New GM ACC Pedal Position Sensor but still throwing P1271 code

[Clooney]

So in January of this year I replaced the ACC Pedal Position Sensor in my 03 TB EXT with the 4.2 after getting a P1271 code. It started throwing the code shortly there after when we had a week long rain event. I started to notice that after the moisture in the air had passed, it works fine. This week it has been very humid and now the code and reduced engine power is back like crazy. I keep a small dehumidifier in it but this week has been brutal with moisture and it quickly got full. Usually I can clear the code while driving and it goes away, but not now. As soon as I clear it, it reappears.

Does anyone know why or what the moisture is affecting, I cant imagine it being the new pedal sensor.

At a loss right now!!

 

[TJBaker57]

So in January of this year I replaced the ACC Pedal Position Sensor in my 03 TB EXT with the 4.2 after getting a P1271 code. It started throwing the code shortly there after when we had a week long rain event. I started to notice that after the moisture in the air had passed, it works fine. This week it has been very humid and now the code and reduced engine power is back like crazy. I keep a small dehumidifier in it but this week has been brutal with moisture and it quickly got full. Usually I can clear the code while driving and it goes away, but not now. As soon as I clear it, it reappears.

Does anyone know why or what the moisture is affecting, I cant imagine it being the new pedal sensor.

At a loss right now!!

It cannot be said often enough that codes never automatically mean a particular part is bad and needs replacing. Codes only identify a symptom of the system. A test that the system did not pass. In this case it sees a mismatch between the two sensors of the accelerator pedal. It could just as easily be a bad spot on any of the 6 wires that connect the accelerator pedal sensor(s) to the PCM. Could be a faulty connection at the PCM connector 1 where that sensor connects.

Best approach is to read the data that the PCM is seeing to see what is happening. Read the freeze frame data to see if there is anything useful there. Short of that, pull the C1 connector at the PCM, inspect, clean etc. Look very closely at the wiring harness for any spots that look suspicious and so on.

 

[TJBaker57]

Additionally, the 5 volt power sources that supply the accelerator pedal sensors are shared by other sensors on the vehicle. So if there is an issue with some of that wiring it is possible for that to cause an issue with the accelerator pedal system. One common such issue is with the engine cooling fan speed sensor wiring which is out of sight in front of the fan clutch.

 

[mrrsm]

As per this friction wear short...

 

[Clooney]

Thank you guys, I'll have my mechanic check the cooling fan wires.

 

[Mramses]

It cannot be said often enough that codes never automatically mean a particular part is bad and needs replacing. Codes only identify a symptom of the system. A test that the system did not pass. In this case it sees a mismatch between the two sensors of the accelerator pedal. It could just as easily be a bad spot on any of the 6 wires that connect the accelerator pedal sensor(s) to the PCM. Could be a faulty connection at the PCM connector 1 where that sensor connects.

Best approach is to read the data that the PCM is seeing to see what is happening. Read the freeze frame data to see if there is anything useful there. Short of that, pull the C1 connector at the PCM, inspect, clean etc. Look very closely at the wiring harness for any spots that look suspicious and so on.

good night friend tjbaker, how have you been?
I have a problem, I have the code p1271… p1635… c037 and c0379. the truck has the "check engine" and "power reduce mode" warning lights
I have the front wheel drive actuator disconnected, as well as the a / c sensor disconnected and the a / c fancluth sensor.
Question: when it is in "reduced power" mode and with the failure of p1271, the gearbox does not make the changes or it has nothing to do with it?
the truck feels when I apply D or any other gear as if it is governed and does not shift or speed. I do not exceed 20km / h

 

[TJBaker57]

I have the code p1271… p1635… c037 and c0379. the truck has the "check engine" and "power reduce mode" warning lights

Hello! Good to hear from you. The P1635 must be the first priority. I believe I once read that our P10 PCM does not have circuit overload protection on the 5 volt reference circuitries. This means the PCM can be damaged if it is allowed to continue to operate in this condition.

Good work so far on removing some of the loads on that 5 Volt ref #1. There are two more on that 5 volt system that you did not mention. The fuel tank pressure sensor and the throttle body position sensor#1. All of these circuits should be tested for a short to ground.

I have the front wheel drive actuator disconnected, as well as the a / c sensor disconnected and the a / c fancluth sensor

You can reconnect the front axle actuator as it has nothing to do with this. That power comes from the TCCM, not the PCM.

Question: when it is in "reduced power" mode and with the failure of p1271, the gearbox does not make the changes or it has nothing to do with it?

Reduced power mode is a safety system. Since there is no physical control of the throttle, the system will not allow high speed operation if there is anything wrong with the throttle control system. This might cause the shifting issues you experience. Even if it did shift it would not be allowed to go faster.

The upper grouping in this picture is the 5 volt reference #1. The lower is 5 volt reference #2

 

[Mramses]

Greetings friends, I have information regarding p1271.
acceleration pedal sensor 1
signal cable with low reference there is variation of the resistance value with the pedal position
but when I measure the signal cable with the 5 v reference there is no change in resistance.
for the other sensor if the resistance varies with a low reference and with a 5v reference with respect to the pedal position. any observations?
question: if I check each of the 5v reference from the pcm output to each sensor and they stay then it is not the cause of p1635?

 

[mrrsm]

There may be a Physical Problem within the ACC Pedal Internal Mechanism to explain WHY this Code P1271 is setting. Always Be Suspicious of Parts that are supposed to be NEW but which may be items Returned to Stock in boxes populated with other Customers' Used-Old Parts:

This Video should appeal to @TJBaker57 's Mechanical Sensibilities and his natural curiosity, too... :>)

 

[TJBaker57]

question: if I check each of the 5v reference from the pcm output to each sensor and they stay then it is not the cause of p1635?

To the best of my knowledge and research, the P1635 operates independent of the Accelerator pedal sensor. The P1635 could be caused by a short of the 5 volt signal to a ground in any of the 5 circuits connected to the 5 volt reference #1, including, but not limited to, the accelerator pedal sensor.





The P1271 appears to have 3 separate, but related, fault scenarios.

sensor 1
signal cable with low reference there is variation of the resistance value with the pedal position
but when I measure the signal cable with the 5 v reference there is no change in resistance.

The only way I can see this is if you had the wrong wires when measuring the 5 volt vs signal wire. The greatest resistance should be seen between the 5 volt and the low reference terminals and this resistance should not vary. From the signal wire to either of the 5 volt or low reference terminals the resistances should vary and these two should be opposite each other as the total resistance seen between the 5 volt and low reference is split between them.

I have just now watched the video linked by @MRRSM and that was interesting in seeing the insides of the sensor. Unfortunate that the fellow did not show a properly illuminated clear view of the circuit board.

Today I intend to do a little experimenting of my own, from the PCM C1 connector end as that us easier to access.

 

[TJBaker57]

So today I made this little graphic up so I would have what I needed without scrolling around in the 2002 wiring diagram...



I probed the PCM C1 connector to read the two APP sensor voltages and observed these while moving the pedal and also watched the PIDs for these sensor outputs in Torque Pro. For 2002 the PIDs are 1478 and 1479. I have no way of knowing if they are the same for later years.

I learned that the PIDs as displayed in the Tech2 as well as any app like Torque Pro are not the raw values. The Pids appear to be massaged into a stable reading while the actual sensor voltages fluctuate slightly. Not surprising really.

Besides that news about the PIDs not being raw values the voltages were seen to rise and fall as expected in response to pedal movements. I also checked the 5 volt references and they were stable. I moved on to resistance tests of the pedal sensor.

I disconnected the PCM C1 connector and used a probe set to make connections to my multimeter(s). Here I began with reading the full resistances seen by the 5 volt circuits of C1:63 to C1:11 for APP sensor #2 and C1:55 to C1:10 for APP sensor #1. Rounding to a single decimal there was about a 200 ohm difference between the two, one was at 4.5k and the other was 4.3k. I verified there were no fluctuations with pedal movement, as expected.

Reading resistances from each sensor output, C1:1 or C1:2, to either the 5 volt terminals, C1;63 or C1:55, or the low reference terminals, C1:11 or C1:10, I observed all the expected variances with pedal movements.

It bears stating that this vehicle has never during my ownership of over ten years had a reduced engine power condition or accelerator position or throttle position error.

 

[Mramses]

So today I made this little graphic up so I would have what I needed without scrolling around in the 2002 wiring diagram...

View attachment 101371

I probed the PCM C1 connector to read the two APP sensor voltages and observed these while moving the pedal and also watched the PIDs for these sensor outputs in Torque Pro. For 2002 the PIDs are 1478 and 1479. I have no way of knowing if they are the same for later years.

I learned that the PIDs as displayed in the Tech2 as well as any app like Torque Pro are not the raw values. The Pids appear to be massaged into a stable reading while the actual sensor voltages fluctuate slightly. Not surprising really.

Besides that news about the PIDs not being raw values the voltages were seen to rise and fall as expected in response to pedal movements. I also checked the 5 volt references and they were stable. I moved on to resistance tests of the pedal sensor.

I disconnected the PCM C1 connector and used a probe set to make connections to my multimeter(s). Here I began with reading the full resistances seen by the 5 volt circuits of C1:63 to C1:11 for APP sensor #2 and C1:55 to C1:10 for APP sensor #1. Rounding to a single decimal there was about a 200 ohm difference between the two, one was at 4.5k and the other was 4.3k. I verified there were no fluctuations with pedal movement, as expected.

Reading resistances from each sensor output, C1:1 or C1:2, to either the 5 volt terminals, C1;63 or C1:55, or the low reference terminals, C1:11 or C1:10, I observed all the expected variances with pedal movements.

It bears stating that this vehicle has never during my ownership of over ten years had a reduced engine power condition or accelerator position or throttle position error.

greetings friends. thanks for answering
I was able to read your tests thanks ... today I plan to corroborate the measurement that does not give me good, I have a stable resistance reading (the resistance does not vary with the variation of the pedal position) between an output signal of one of the sensors and the 5 v from the sensor.
Today I plan to verify those readings and upload them to the thread to discuss them. I am also going to check all the 5v output of the pcm to: map, throttle butterfly, acceleration pedal, a / c pressure sensor ... fanclutch sensor, fuel tank pressure sensor and verify there is no variation.
question: if any of the aforementioned sensors is disconnected, the harness should cause activation of p1635?

 

[budwich]

You probably only need to check the connector at the pedal to ensure it is seated properly and has clean contacts. You never posted what your actual resistance reading is that you are seeing.

 

[TollKeeper]

Theres a recent (last night) episode on South Main Auto about this exact problem... To bad its for a Nissan Sentra, otherwise it would be very helpful

 

[TollKeeper]

So, South Main Auto did one today for an Envoy that may be relevant.

 

[Mramses]

good night friends I hope you are all well. Today take measurements for Accelerator Pedal Sensors 1 and 2. he had indeed performed the first test wrong. In the image that I upload, the values of the resistances of each sensor are shown. Both sensors vary the resistance in the signal cable with respect to the 5v reference and a low reference of each sensor (this with the variation of the pedal position)
For the case of the resistance value between 5v and low reference of each sensor, it gives a fixed resistance value that does not vary with the position of the pedal. so far so good, the values assume that the pedal is good (perform the test several times and exchanging the polarity of the tester)
Now, for the measurement of the 5 v of each sensor I had the following result (the measurement was made directly on the harness being disconnected from the pedal and connected to the pedal gave the same results.
for the 5v of the sensor in the D-connector it measured 5.06v, but for the J-connector it measured 1.92v. I think here is the reason for p1271 and p1635.
To corroborate the interity of the cable from the PCM C1 63 to the pedal connector in J, there is continuity between the ends (22 ohm which is the same when the tester leads are brought into contact) and there is no short circuit to ground or voltage + .
confirm the computer supply voltages at C1 and C3… also confirm the computer ground at C2. everything's fine. I also measured the resistance of each 5v output of the PCM with respect to the mass of the PCM at C2 65 and measured 8.89 on the 20 kohm scale, these resistance values at each 5v output of the PCM and the mass C2 65 were all the same .
I tried with another PCM (not programmed) and it hits the pedal connector at J 2.01 v (too bad you loved PCM's have the same fault)
Is there a way to supply the PCM with ground and 12v voltage to know if the 5v exists in C1 63 without being connected to the wiring harness of the truck?
what to evaluate now? Is there a lack of supply voltage from the PCM? the supply voltages are at the connectors but I am not sure if the PCM receives them since I measured them disconnected from the PCM. or could I have 2 PCM with the same fault in the 5v output on C1 63?

 

[TJBaker57]

I would measure each of the other circuits that use that 5 volt ref #1 to ground, at the disconnected PCM harness.

C1:54 to ground
C1:62 to ground
C1:63 to ground
C3:3 to ground
C3:60 to ground

Here I show measuring C1:54 to ground... (The meter displays "1" when the circuit is "open")



None of the mesaurements listed above should show a low resistance.

 

[Mramses]

I would measure each of the other circuits that use that 5 volt ref #1 to ground, at the disconnected PCM harness.

C1:54 to ground
C1:62 to ground
C1:63 to ground
C3:3 to ground
C3:60 to ground

Here I show measuring C1:54 to ground... (The meter displays "1" when the circuit is "open")

View attachment 101388

None of the mesaurements listed above should show a low resistance.

 

[Mramses]

hello friend tjbaker nice to greet you brother
I only made the measurement of C1 63 to ground and to the cable + from the branch to the battery to check if there was a short to ground or to power, both measurements gave me infinity.
I did not measure the rest of the 5v outputs but I did verify that they had 5v with respect to ground by turning the switch to RUN.
Question: can the PCM (test bench type) be powered with voltage and ground, to check the 5v outputs without being connected to the truck? This is because, I tried with another PCM (not programmed… when giving START the anti-theft is activated, but being only in RUN it activates the 5v) and in the pedal connector in J medi 2.06 v for this second PCM.
When I measure resistance between C1 63 and C2 65 I get 8.89 (20kohm) in a PCM, giving the pedal connector J 1.92 v and in the other PCM I measure 8.01 (20kohm) giving the pedal connector J 2.10 v.
You could get the internal diagram of the PCM, where you could see where each 5v circuit comes from at the PCM output and know if they all come from the same component or are independent.

 

[Mramses]

I would measure each of the other circuits that use that 5 volt ref #1 to ground, at the disconnected PCM harness.

C1:54 to ground
C1:62 to ground
C1:63 to ground
C3:3 to ground
C3:60 to ground

Here I show measuring C1:54 to ground... (The meter displays "1" when the circuit is "open")

View attachment 101388

None of the mesaurements listed above should show a low resistance.

I could only check C1 63 to ground and cable + to the battery, both give infinite resistance.
can be powered with 12v in C1: 19,20 and 21 C3: 17
and giving mass in C2: 65
to get the 5v outputs from the PCM and check their integrity?
Could a plan be located where the output diagrams of each 5v of the PCM are specified? Will they all be from the same component or are they from independent circuits?

 

[TJBaker57]

Could a plan be located where the output diagrams of each 5v of the PCM are specified? Will they all be from the same component or are they from independent circuits?

I have made these measurements of the PCM 5 volts circuits last year. The listing I pictured with the green and the yellow colors (in message number 7) indicates the two 5 volt reference circuits. 5 volt reference #1 is colored green in that chart. 5 volt reference #2 is colored yellow. All 5 of the terminals I gave you to measure at message number 17 above here are connected inside the PCM to same 5 volt source. Because of this, if any one of those circuits has a short to ground then the 5 volt source will be brought low by the overload. This is why you must test all 5 of those circuits for a short to ground.

 

[Mramses]

Hello! Good to hear from you. The P1635 must be the first priority. I believe I once read that our P10 PCM does not have circuit overload protection on the 5 volt reference circuitries. This means the PCM can be damaged if it is allowed to continue to operate in this condition.

Good work so far on removing some of the loads on that 5 Volt ref #1. There are two more on that 5 volt system that you did not mention. The fuel tank pressure sensor and the throttle body position sensor#1. All of these circuits should be tested for a short to ground.





You can reconnect the front axle actuator as it has nothing to do with this. That power comes from the TCCM, not the PCM.




Reduced power mode is a safety system. Since there is no physical control of the throttle, the system will not allow high speed operation if there is anything wrong with the throttle control system. This might cause the shifting issues you experience. Even if it did shift it would not be allowed to go faster.

The upper grouping in this picture is the 5 volt reference #1. The lower is 5 volt reference #2

View attachment 101367

friend I do not understand the table very well. those are measurements obtained in the connectors of each sensor that receives the 5v? or is it a reference table? please if you could explain me a little

 

[TJBaker57]

friend I do not understand the table very well. those are measurements obtained in the connectors of each sensor that receives the 5v? or is it a reference table? please if you could explain me a little

Inside the PCM there are only two different 5 volt reference power supplies. This can be seen with a Tech 2 or Tech2Win in the selection of TAC data seen here...



Each of the two 5 volt reference supplies provides power to more than one sensor circuit that requires a 5 volt power source. There are not separate 5 volt power supplies for each sensor. Inside the PCM several sensors 5 volt reference connections will connect to the same point.

Last year when we were testing resistances on PCMs I also tested continuity between the pins for the 5 volt reference terminals. By doing this I learned which of the many 5 volt reference terminals of the PCM are connected together inside the PCM. The table displays which sensors use 5 volt reference signal #1, and which sensors use 5 volt reference signal #2. At the time I did the tests I did not know which group was 5 volt reference #1 and which was 5 volt reference #2 but I have recently learned this so I have now added that to the table. (Edit: I also reorganized the table for clarity)






So looking at the table, and knowing there are 5 sensors that are connected to 5 volt reference signal #1, and knowing that these are all connected together inside the PCM, you can then know that if for example the 5 volt fuel tank pressure sensor circuit or the 5 volt cooling fan speed sensor circuit is damaged and contacts a ground then all 5 of the sensors that use 5 volt reference signal #1 will be affected.

 

[mrrsm]

I know that Thomas will want to Take a Swing at My Chin... but in this situation, it will be helpful NOT to rely too much on Scan Data. This is because the Signal Information gets averaged and cleaned up in such a manner as to obscure what is really going on.

Since we are getting so far into the technical weeds now in our search for a solution, I'm suggesting that the OP might invest in and obtain an inexpensive Hantek 1008C or PICO Scan 2204A Oscilloscope, as these are the ONLY Tools that will detect and resolve the fine grain aspects of what is actually happening in between the PCM and the ACC Pedal and-or Throttle Position Sensor Modules.

In this Video, the VOP (Video Original Poster) is the Training Instructor for "Dead On Diagnostics" who thoughtfully explains What the Value of these Tools are and How to Use them in order to sort things out:

In this instance... The Analytics of Multiple Position Sensors (Throttle Body Module, ACC Pedal Module, Brake Pedal, etc.)

 

[TJBaker57]

I know that Thomas will want to Take a Swing at My Chin... but in this situation, it will be helpful NOT to rely too much on Scan Data.

Not at alll !! I only included the picture of the Tech 2 as a reference to there being two 5 volt reference sources, numbers 1 and 2. The language barrier being what it is I thought a picture might help.

It is likely scan data for any of the five circuits on 5 volt reference #1 will show an out of range condition since it appears the 5 volt reference is being dragged down by an as of yet unknown condition or fault.

Back in post #7 I stated the P1635 is top priority. I still stand by that statement as that by itself will cause these other faults in the accelerator pedal and throttle position sensors.

However we divert here in our approach as I think this can be handled by fundamental testing with a multimeter coupled with a clear understanding of the system circuitry.

 

[Mramses]

Inside the PCM there are only two different 5 volt reference power supplies. This can be seen with a Tech 2 or Tech2Win in the selection of TAC data seen here...

View attachment 101390

Each of the two 5 volt reference supplies provides power to more than one sensor circuit that requires a 5 volt power source. There are not separate 5 volt power supplies for each sensor. Inside the PCM several sensors 5 volt reference connections will connect to the same point.

Last year when we were testing resistances on PCMs I also tested continuity between the pins for the 5 volt reference terminals. By doing this I learned which of the many 5 volt reference terminals of the PCM are connected together inside the PCM. The table displays which sensors use 5 volt reference signal #1, and which sensors use 5 volt reference signal #2. At the time I did the tests I did not know which group was 5 volt reference #1 and which was 5 volt reference #2 but I have recently learned this so I have now added that to the table. (Edit: I also reorganized the table for clarity)



View attachment 101391


So looking at the table, and knowing there are 5 sensors that are connected to 5 volt reference signal #1, and knowing that these are all connected together inside the PCM, you can then know that if for example the 5 volt fuel tank pressure sensor circuit or the 5 volt cooling fan speed sensor circuit is damaged and contacts a ground then all 5 of the sensors that use 5 volt reference signal #1 will be affected.

good afternoon to all friends. Following the steps indicated by tjbaker, I set out to measure each 5v output on PCM connectors C1, C2 and C3. This was the sequence of resistance measurements, I started at C1 54,55,62 and 63, none of them gave a short to ground or to the power supply positive cable. then I measured C2 64 there is no short to ground or positive. finally C3 3,49 and 60… bingo: this last C3 60 was short to ground. disconnect the harness from the fanclutch and the short to ground is eliminated.
I am about to connect the battery, I turn the switch to RUN and measure the 5v for sensor 2 of the pedal and I have 5.06 v (thanks to you I did not go straight to buy the pedal and lose money)
take advantage and measure all the 5v of all the sensors that governs the PCM and all ok.
Observation: when connecting the branch to the pedal the voltage drops from 5.06v to 4.01v (is it normal?) then I connect the vxdiag (thanks to this cheap scanner) and read the PCM codes and there was the p1271, p1635 and u1000 (remember I have modules from my original truck and those acquired in the drain) ... I proceed to erase the DTCs and they do not return, no more p1271 or p1635 ... I only have the u1000 which requires reprogramming. Question: why was it C3 60 5v ref a short to ground fanclutch the rest of the sensors linked to the 5v source were fine except for the 5v of the acceleration pedal? I was left with the doubt friends.
Another question: I could not start the truck due to a lack of battery charge, but I think the checkengine and the reduced power indicator should be eliminated.
thanks to all, tomorrow I have to locate another borrowed battery to turn on and scan with vxdiag again and confirm the result of the diagnosis, I cross my fingers so that I accelerated well and start changing the transmission

 

[TJBaker57]

Question: why was it C3 60 5v ref a short to ground fanclutch the rest of the sensors linked to the 5v source were fine except for the 5v of the acceleration pedal? I was left with the doubt friends.

If the truck was able to operate longer then the other sensors would likely set error codes. But because the throttle control is a serious safety concern that system reacts faster to set codes and prevent unsafe operation of the truck.

Observation: when connecting the branch to the pedal the voltage drops from 5.06v to 4.01v (is it normal?)

This may be due to the low battery charge you spoke of.

 

[Mramses]

Good morning friends, how are you all, greetings.
good according to the result of the diagnosis achieved by all and in advance thank you very much. effectively, when disconnecting the harness from the fanclutch (short to ground) the 5v is reestablished in the pedal sensor that had 1.92v. After this, the codes are reset and the code P1271 and P1635 is effectively erased. then it is scanned again and the codes do not reappear but the one for the disconnected fanclutch and a fuel trim code.
I was able to start the truck (there was no fuel in my city in Venezuela and it remains to test that the box makes the changes.
PS: the engine reduced power warning light with the arrow pointing down was deactivated.

 

[59840Surfer]

I've read each post in this particular thread to see when/if someone would decide to look at the resistance in each pedal sensor. It finally happened, but I was chagrined to see it not developed further.

I was popping codes for the throttle position sensors and they were consistent in their failure... sometimes happening spontaneously and something after hitting a moderately sharp impact in the road.

Spontaneously happening is a consistency in my mind, so ... running with that as the sole base for my exploration ... I tried to duplicate spontaneousthings ... looking for the cause.

Prior to me getting this vehicle ... my son put a new throttle assembly in it ... but it seemed to not be the cure.

Getting down to actually testing "things" that could be spontaneous, I will list some of my observations.....

1. Hitting a bump would sometimes pop the REP/CEL.
2. Starting the car in very cold weather and letting it idle for 10 minutes or so .... would sometimes pop the REP/CEL.
3. Running on Cruise Control for 40 minutes or so would sometimes pop the REP/CEL.
4. Using heavy throttle in a passing situation, would sometimes pop the REP/CEL.
5. Restarting the engine after I ate lunch at Burger King, would sometimes pop the REP/CEL.
6. Changing spots where I was fishing and driving less than 1/4 mile or so to a different spot would sometimes pop the REP/CEL.
7. Driving uphill backwards would sometimes pop the REP/CEL.

All in all ... much too varied to find a theme.

So I bought a 2 channel oscilloscope and watched the throttle sensors both at the same time .... I found it!

There was a small amount of what I'll call "chatter" happening on the #2 sensor while it was in it's "home position" with no throttle application ...... IOW ---> the resistance moved ever so imperceptibly... not really changing enough or with a slow enough frequency for a DVOM to see it .... but the oscilloscope did!

I actually cleaned that potentiometer with MAP Cleaner, leaving it intensely clean but unlubricated.

The problem has yet to reappear and it makes me happy to take Burger King off my bad places to go list.

☆ If anyone reading this post eats at McDonalds and has UTD (Unable To Diagnose) REP/CELs, well .... you and your stomach are on your own.



.

 

[mrrsm]