A lot of codes, reduced power

Russ

Original poster
Member
Jan 4, 2012
43
Just got home from Hawaii for Christmas and my daughter tells me her 2002 Trailblazer's check engine light is on and reduced power light is on. I put the reader on the car and this is what I come up with: P0495, P0105,P0507,P1516,P1512,P1482.

Any ideas where I should start first? Only home til the first of the year, then back to Hawaii for another 30 days.

Thanks in advanced

Russ
 

limequat

Member
Dec 8, 2011
519
Russ said:
Just got home from Hawaii for Christmas and my daughter tells me her 2002 Trailblazer's check engine light is on and reduced power light is on. I put the reader on the car and this is what I come up with: P0495, P0105,P0507,P1516,P1512,P1482.

Any ideas where I should start first? Only home til the first of the year, then back to Hawaii for another 30 days.

Thanks in advanced

Russ

You got a lot going on there:

Fan, MAP, Throttle, idle speed.

I'd suggest replacing the PCM.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Or looking for a shorted/open wiring harness in the vicinity of the 5V reference line that connects many of those mentioned systems.
 

CaptainXL

Member
Dec 4, 2011
2,445
Yeah that's the infamous fan clutch harness short issue if I'm not mistaken. Which causes throttle codes and such.
 

Russ

Original poster
Member
Jan 4, 2012
43
the roadie said:
Or looking for a shorted/open wiring harness in the vicinity of the 5V reference line that connects many of those mentioned systems.


Where is the "5V reference line"? I know it must come off the PCM but is it a special wire/bundle?

Again, thanks in advance

Russ
 

Russ

Original poster
Member
Jan 4, 2012
43
CaptainXL said:
Yeah that's the infamous fan clutch harness short issue if I'm not mistaken. Which causes throttle codes and such.

I replaced the clutch fan awhile ago and yet it still roars. Could a short be causing the roaring?

Thanks

Russ
 

The_Roadie

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Nov 19, 2011
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Portland, OR
Replacing the fan clutch is a very relevant issue, and I should have asked first if there was any maintenance history on the truck. Anything else?

The 5V reference wire is in the normal fat harness that goes everywhere from the PCM. To measure it, you need to poke through the wire with a needle, or poke in the back of a connector body at the right wire. We have schematics available in a thread here with "get your manuals" in the title. Do you have experience with electrical troubleshooting and want to follow some schematics? Otherwise a good first step, especially with a roaring fan, is to just disconnect the fan clutch harness at the fan and see if its behavior changes. It could be a short or open in the wiring, a bad clutch (depending on whose you bought) or a bad control relay.

The Efan installation should be the subject of its own thread, so as to not hijack this one. Unless you know for sure the Efan controller (whose did you buy?) isn't the root cause.

Here's the fan clutch schematic:

FanClutchSchematic.jpg
 

Russ

Original poster
Member
Jan 4, 2012
43
Roadie,

I have almost no experience with electrical problems.Learning as I go here, from the best. The fan clutch I bought from RockAuto and if I remember correctly, it was from Dorman. It howled right after I installed it.

The other maintenance performed has been basic stuff. TB removed, cleaned. Plugs replaced. One coil replaced. Shocks, tierods, etc.

Thanks

Russ
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Dormans aren't recommended for fan clutches because of high failure rate. Yours could have been a return, or bad out of the box, but why didn't you have a conversation with Rockauto at the time you put it in? Does it always sound like an F16 on afterburner, or just for the first minute or two? A roar that goes away is normal.

Is the vehicle driveable now? Does the REP mode ever go away? Is it permanent or intermittent?

As I said - for the first thing, see if it's a permanent REP problem, then pull the fan clutch connector to see if the 5V reference issue is down inside the fan clutch.
 

Russ

Original poster
Member
Jan 4, 2012
43
the roadie said:
Dormans aren't recommended for fan clutches because of high failure rate. Yours could have been a return, or bad out of the box, but why didn't you have a conversation with Rockauto at the time you put it in? Does it always sound like an F16 on afterburner, or just for the first minute or two? A roar that goes away is normal.

Is the vehicle driveable now? Does the REP mode ever go away? Is it permanent or intermittent?

As I said - for the first thing, see if it's a permanent REP problem, then pull the fan clutch connector to see if the 5V reference issue is down inside the fan clutch.

Roadie,

I do appreciate you taking time to help me.

The fan really only roars when starting up. Eventually it goes away. So, I guess it's normal. Trying to get the daughter to explain what's happening is difficult. :crazy:

When it first happened, it wouldn't start. Then she got it running and it ran fine. When she stopped for gas, she shut it off and when she started it again, it was in reduced power mode again and the whole car was shaking. She shut it off again and let it sit for a few minutes. She then started it and drove it home without REP. Again, she parked it and when she started it again, it was again in REP. And that's how it is now.

Hoping it may be something simple like just replacing PCM. Not cheap but simple.

Thanks again

Russ
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
It may be a chafed harness going to the accelerator pedal assembly, or the pedal assy itself.

Without some deep electrical troubleshooting work, your best bet may be to take it to somebody with a high end scan tool or GM Tech II that can ask the PCM to read the five sensors involved in the 5V reference circuit (2 on the accel pedal, 2 on the throttle body, and one on the fan clutch). If replacing the PCM is even on the table as a desperation cure, you will want to get a guaranteed diagnosis before spending money that might ultimately be wasted. Locate an honest independent mechanic with experience on drive-by-wire systems and GMT360 schematics, or use a dealer. But my strong recommendation is to not spend money unless you KNOW what the root cause is, and I don't think anybody here can give you that process. Personally, I'd spend a couple of hours examining the wiring to the accel pedal, throttle body, fan clutch, and PCM before taking it to a professional. I'm lucky enough to have such a professional, independent GM-only shop nearby, for the sticky ones I need help fixing. I never bring him electrical problems, but things like broken bolts or transmission servicing I just don't do well on. (I have an aversion to transmission fluid due to an incident 40 years ago, for instance.) :redface:
 

Russ

Original poster
Member
Jan 4, 2012
43
I'll have to ask my cousin if he can use his GM Tech II scanner on it. He works for a Buick/GMC dealership but does a lot of work on the side.

Wish me luck.

Thanks Roadie

Russ
 

2007TB

Member
Dec 30, 2012
1
My Wife has a 2007 TB I6 4.2L and had loss of power and driving like Sh*t. When driving it would try to shut off every so often. Check engine light was on and multiple trouble codes too. The P0495 code sounds familiar to me but I didn't save the codes... Tried Auto Zone, Pep boys and they could not tell me what the codes meant.

I took it in to NTB and they said it was the MAF Sensor after diagnosing it for over 2 hours. It was dirty and was going bad. They replaced it and did a fuel system cleaner including the throttle body. The truck runs like new now with 80,000. Mass Airflow sensor is pretty easy to replace so maybe start with that and disconnect the battery for a bit to reset the PCM. Try some seafoam cleaner so you can spray into the Throttle Body directly but NOT the MAF SENSOR since it would damage it. It might remove any carbon build up in the intake. If the MAF Sensor does not fix it return it and say it was never mounted. Hope it helps! Good luck!


Russ said:
Roadie,

I do appreciate you taking time to help me.

The fan really only roars when starting up. Eventually it goes away. So, I guess it's normal. Trying to get the daughter to explain what's happening is difficult. :crazy:

When it first happened, it wouldn't start. Then she got it running and it ran fine. When she stopped for gas, she shut it off and when she started it again, it was in reduced power mode again and the whole car was shaking. She shut it off again and let it sit for a few minutes. She then started it and drove it home without REP. Again, she parked it and when she started it again, it was again in REP. And that's how it is now.

Hoping it may be something simple like just replacing PCM. Not cheap but simple.

Thanks again

Russ
 

Russ

Original poster
Member
Jan 4, 2012
43
2007TB said:
My Wife has a 2007 TB I6 4.2L and had loss of power and driving like Sh*t. When driving it would try to shut off every so often. Check engine light was on and multiple trouble codes too. The P0495 code sounds familiar to me but I didn't save the codes... Tried Auto Zone, Pep boys and they could not tell me what the codes meant.

I took it in to NTB and they said it was the MAF Sensor after diagnosing it for over 2 hours. It was dirty and was going bad. They replaced it and did a fuel system cleaner including the throttle body. The truck runs like new now with 80,000. Mass Airflow sensor is pretty easy to replace so maybe start with that and disconnect the battery for a bit to reset the PCM. Try some seafoam cleaner so you can spray into the Throttle Body directly but NOT the MAF SENSOR since it would damage it. It might remove any carbon build up in the intake. If the MAF Sensor does not fix it return it and say it was never mounted. Hope it helps! Good luck!

The 2002 Trailblazer doesn't have MAF sensor. I've cleaned the throttle body and that didn't seem to help.

Leaving for Hawaii on the 2nd, so it will have to wait til I get back in Feb.

Thanks

Russ
 

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