P1680 diagnostic

KNBlazer

Original poster
Member
Feb 8, 2012
811
On the gas pedal, are the two pins that are tested, the bottom two?

yduzypyq.jpg


Once I press the pedal, I get a reading of 800-840 ohms.... I remember reading anything over 450 was good, right?

I guess an update will be my solution...
 

IllogicTC

Member
Dec 30, 2013
3,452
KNBlazer said:
On the gas pedal, are the two pins that are tested, the bottom two?

yduzypyq.jpg


Once I press the pedal, I get a reading of 800-840 ohms.... I remember reading anything over 450 was good, right?

I guess an update will be my solution...

Not sure, but I can help with understanding the wiring. I'm not sure on the orientation to know which pin is pin A, so we can go off the color of the wires to determine that.

Pin A - Purple - Low Reference (APP 2)
Pin B - Light Blue - Accelerator Pedal Position Sensor 2 Signal
Pin C - Tan - 5V Reference
Pin D - Brown - Low Reference (APP 1)
Pin E - Dark Blue - Accelerator Pedal Position Sensor 1 Signal
Pin F - White/Black - 5V Reference

Also, as far as I know, the P1680 is a Powertrain Control Module Fault. If there was an issue with the accelerator pedal the reduced power light should also appear, did it or no? It may still involve the pedal anyway, but here is more likely your issue:

TSB

Models: 2004 Buick Rainier

2004 Chevrolet Trailblazer

2004 GMC Envoy

2004 Oldsmobile Bravada

with 4.2L Engine (VIN S - RPO LL8)

Some customers may comment on the Service Engine Soon Light coming on. Upon investigation, the technician may find a P1680 diagnostic trouble code. Check the resistance of the accelerator pedal position sensors using the procedure in the appropriate Service Information for DTC P1680.

If the resistance of the accelerator pedal position sensor is within the specifications shown in the Service Information and the vehicle was built prior to the following VIN breakpoints, then reprogram the PCM with the latest calibration.

If the resistance of the accelerator pedal position sensor is within the specifications shown in the Service Information and the vehicle was built after the following VIN breakpoints, then replace the PCM. If the resistance of the accelerator pedal position sensor is outside the specifications shown in the Service Information, then continue with the diagnostics for DTC P1680.

VIN Breakpoints for the issue:

Vehicles built at Oklahoma City Assembly Plant - 46192755

Vehicles built at Moraine Assembly Plant - 42315833
 
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KNBlazer

Original poster
Member
Feb 8, 2012
811
Thanks, I had seen a variant of this TSB minus the wire color legend....I do get Reduced Power.... I think it's the two 5v pins I need to test....
 

IllogicTC

Member
Dec 30, 2013
3,452
I provided the wire color legend so you can better understand what pins are supposed to do what when testing your sensor, just in case. I don't know the exact values on what defines "good" resistances, but if I remember right the two sensors are opposed to each other. Meaning at 0% one reads high and the other low, and at 100% one reads low and the other high. Perhaps you can compare the resistances of the two sensors to better understand how they're working and if it's within a decent range.
 

bobdec

Member
Apr 19, 2013
233
I would first test resistance in between pins A (sensor 2 ground) black meter lead and pin B (sensor 2 output) red meter lead. The resistance should swing with the pedal movement, Record the Hi/low points . Next meter pin D (sensor 1 ground) black meter lead and pin E (sensor 1 output) the readings should be the same resistance swing , BUT move in the OPPOSITE direction. Look for differences in the resistance hi to low between sensor 1 and 2, also look for a smooth flow without any dead or hot spots while moving the pedal slowly.
Another better test would be to w/key on engine off, plug in the connector, use a straight pin to pierce the wires and check voltage on pins B to ground and pin E to ground. One should move from about 0 to 5 Volts and the other should move 5 to 0 volts as pedal is depressed. NOTE... voltage is not exactly 0 and 5 volts, just make sure the high/low's are equal, they move in opposite directions, also smooth change, no jumps or drops as pedal is moved..
 

mrrsm

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Here is the Complete Text of the Related TSB:

TECHNICAL SERVICE BULLETIN

Reference Number(s): 04-06-04-038, Date of Issue: June 14, 2004

Affected Model(s):

2004 Buick Rainier; 2004 Chevrolet Trailblazer; 2004 GMC Envoy; 2004 Oldsmobile Bravada; with 4.2L Engine (VIN S - RPO LL8)

Related Ref Number(s): 04-06-04-038

ARTICLE BEGINNING

CONDITION


Some customers may comment on the Service Engine Soon Light coming on. Upon investigation, the technician may find a P1680 diagnostic trouble code.

CORRECTION

Check the resistance of the accelerator pedal position sensors using the procedure in the appropriate Service Information for DTC P1680. If the resistance of the accelerator pedal position sensor is within the specifications shown in the Service Information and the vehicle was built prior to the following VIN breakpoints, then reprogram the PCM with the latest calibration.

If the resistance of the accelerator pedal position sensor is within the specifications shown in the Service Information and the vehicle was built after the following VIN breakpoints, then replace the PCM. If the resistance of the accelerator pedal position sensor is outside the specifications shown in the Service Information, then continue with the diagnostics for DTC P1680.

VIN Breakpoints

Vehicles built at Oklahoma City Assembly ◦ Plant - 46192755
Vehicles built at Moraine Assembly Plant - 42315833

The new calibration will be released beginning with TIS satellite data update version 1.5 for 2004, available January 2004. As always, make sure your TECH2(R) is updated with the latest software version.

PARTS INFORMATION

Parts Information

Part Number Description Qty


12574976 Module, Powertrain Control 1 as Req'd

Parts are currently available from GMSPO. Service Engine Soon Light On, P1680 (Reprogram or Replace PCM) -2004 GMC Envoy Page 1 of 2

http://www.ondemand5.com/mric/common/asp/printart.aspx

12/1/2011

WARRANTY INFORMATION

For vehicles repaired under the applicable 8 year/80,000 mile (130,000 kilometer) emission controller warranty, use:

Warranty Information

Labor Operation Description Labor Time


J6353 Module, Powertrain Control - Reprogram 0.4 hr
Add: Diagnostic Time 0.0-0.3 hr

J6360 Module, PCM/VCM - Replace 0.9 hr
Add: Diagnostic Time 0.0-0.3 hr


If needed... The GM PCM Part# 12574976 for the 2003-2005 Trailblazer-Envoy SUVs is presently available (10/17/2020) over on eBay and the Pricing Starts at around $35.00:

 
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Dadwagon

Member
May 21, 2020
141
West coast
Appears bringing the vehicle to a GM dealer is required for getting this issue fixed. This reflashing of the PCM seems to fix a few of the electrical problems with the GMT360s.
 

mrrsm

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They will Charge you around $100.00 just for the Re-Flash...which is roughly 1/3 of the cost of buying either a "GYMKO" (General Motors Knock Off) Tech 2 for around Three Bills or a VXDiag Nano style Unit for even less... and having solved that ONE Problem, the Question Begs:

"What will you do if you need the Dealership Tech 2 again for the NEXT issue that requires it?"

If you feel that your Skill Set with Learning and Using such Equipment is within your "Mechanic's Wheel House"... Check out THIS Thread for the MOST recent and contemporary Posts about those that have successfully purchased either the Tech 2 or some Alternative version of the Gear necessary for communicating with the PCM and Read-Write the Updates on your own:


It would be very helpful if others who have "taken the plunge" would chime in with their suggestions and recent experiences with getting their own "GYMKO" Tech 2 or one of the Higher End Scanner Alternatives as well.

@Expeditor ???
 
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Dadwagon

Member
May 21, 2020
141
West coast
I was leery of getting a knockoff Tech 2 device in case it failed to work with my Rainier. And I can't afford to buy a legit GM Tech 2, even used they are out of my price range. Honestly I have no time to bring the truck to the dealership anyways given work and childcare, so I am open to trying one. The computer work isn't an issue, it's the knockoff being a worthless expensive brick that I can't return.
 

Reprise

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And I can't afford to buy a legit GM Tech 2, even used they are out of my price range

Check your local Craigslist, if you haven't already. That's where I found my real deal Vetronix, courtesy of a retired service tech.
 
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mrrsm

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Well... I'm not certain where you obtained the idea that getting a "Bricked Tech 2" will be the expected outcome, so I can't do any more than suggest that you visit the Tech 2 Sub-Forum (Set up by @Mooseman) and perhaps browse around.

While checking all of the many resources there, you'll be able to read through the various Threads posted over the last 3-5 years and see if your opinion changes based upon the very favorable experiences presented there by other GMTN Members.

Other than that, if you have to go the Dealership Route, I'm with those of us who'll wish you well with the sincere hope that this issue will finally be resolved in your favor. One last thought... Right now, you'll have NO Idea just how COOL this Cool Blue Light looks that comes off of the Tech 2 Screen ... until you Own One:

GYMKOTECH2KIT.jpg
 
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JayArr

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Sep 24, 2018
504
Mission BC Canada
I paid a lot for my knock off and it's worked beautifully. It's paid for itself many times over in just two years. I diagnosed a bad wiring harness to a fan clutch with it while sitting in a campsite on vacation.

Imagine your wife's face while sitting in a dealership while on vacation waiting for the car to be repaired and then tell me you won't spend $500 to avoid that look! The dealership is going to take $500 of your money anyway.

Live data while driving down the road is fantastic when looking for a problem, clearing a CEL without even stopping the car, interactive menus that allow things to be forced on/off can cut diagnostic time by half or more.

I think your fear of it not working with the Rainier is misplaced. It's the same PCM from the same Delphi factory as the Envoy and Trailblazer.
 
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Reprise

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I think your fear of it not working with the Rainier is misplaced. It's the same PCM from the same Delphi factory as the Envoy and Trailblazer.

I think he meant, with it being a clone, that it might not work "at all" (with any vehicle), not just his Rainier. That was how I took it. Also, as an aside, it also communicates with the BCM and everything on the CANbus, not just the PCM. And probably some other things I've forgotten, as well.

To be fair, I think the GMTN people who've bought their clones have fared pretty well -- everyone got their devices (some waiting longer than others), and they all seem to work OK as a 1-1 replacement, vs. the 'genuine' ones. I'd definitely research my vendors before sending a wad of cash to China.

Right now, you'll have NO Idea just how COOL this Cool Blue Light looks that comes off of the Tech 2 Screen ... until you Own One:

Are you looking at this parked in the garage, with the lights out? LOL

Generally, when I look at the screen, I'm thinking "gee, this thing is really old, and the UI / menuing is really slow to navigate". Not to mention that things can be hard to find (for me, at least). Some competing high-end devices are easier to navigate / better UI. They also cost arm / leg / firstborn.

But I am glad I have mine. :2thumbsup:
 
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JayArr

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Sep 24, 2018
504
Mission BC Canada
That makes more sense, I thought he had a fear that it wouldn't work with just his Rainier.

I buy stuff from China through eBay three or four times a week. I run an electronic repair company and China is where all the parts are. I've got to say I've always gotten my $$ back on anything I wasn't happy with, eBay is pretty good at settling up, sometimes it takes them a few days but if what I was sold doesn't work, isn't what they advertised or is just plain junk I just start a complaint and get the $$ back.

JayArr
 
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Mooseman

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Dec 4, 2011
25,262
Ottawa, ON
As one of the earlier adopters of one of these clones, it's been a blessing. I got charged $150 at the dealer just for a CASE relearn so when I saw these clones for $300 at the time, I jumped on it. Hell, I even paid it off by putting an ad on Kijiji and scanning and doing stuff for people for a modest sum (until Kijiji started charging for "commercial" ads). Just love thumbing my nose at the dealer.

Just one warning. Buy one from a seller with stock in the US as US Customs has been seizing them and fining those importing them as trademark infringement. (Does not affect Canada)
 

Reprise

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I buy stuff from China through eBay three or four times a week. I run an electronic repair company and China is where all the parts are.
Word. Every-frickin-thing is made there.
I did get burned on an item, once (long story, not an auto part). I got the item, but it wasn't what I ordered. Even got a response from the seller, over in China. In the end, I ate about $135.

Just one warning. Buy one from a seller with stock in the US as US Customs has been seizing them and fining those importing them as trademark infringement. (Does not affect Canada)


I was going to mention this exact thing. And I was wondering how loosely Canada ran their customs, compared to us (you guys aren't in a trade war with China, for starters.)

Along these lines, I was going to suggest perhaps using a Canadian liaison to use as the go-between, if one was worried about US Customs.
Obviously, this works better if you *know* a Canuck. 🇨🇦
 

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