2002 trailblazer P1275 &P1280 Pedal doesn't respond at all

Hello there! I got a 2002 trailblazer with 151298 miles and p1275 and p1280 code on the scanner! I also have reduced engine power. I've cleaned the grounds, checked the wires from the pcm🤔🤔. Tps looks great. No blown fuses. Other then replacing the pedal sensor which I'm told 99% isn't the issue I'm having a hard time figuring the problem. I'm not just trying to replace stuff I'm trying to learn why. I did see something about fan clutch can effect acceleration. But mine doesn't do anything. HELP PLEASE!
 

MRRSM

Lifetime VIP Supporter
Welcome Aboard GMT Nation!

These Prior GMTN Related Threads are worth looking over:


...and another [SOLVED] from over at TV that covers the solution of things in fine grained detail:


NOTE: If it turns out to that your PCM is "T*TS UP" scour eBay as there may be some available for not too much Moolah... :>)
 

budwich

Well-Known Member
"checked the wires from the pcm🤔🤔." hopefully with a meter and not your eyes... I have never seen electricity but my meter has... :smile:

You want to do some "end to end" measurements (from one end and then the other, check the schmetics to determine what the "makeup" of the circuit is, and what to expect), both voltage wise and resistance wise to determine if the circuit involved are in deed "good".
 

Mooseman

Moderator
You can also try unplugging the radiator fan connector. It's known to sometimes cause a short in the 5v reference line, which is shared with the APP and throttle sensors.
 
OP
OP
L

Lifechanger

Member
You can also try unplugging the radiator fan connector. It's known to sometimes cause a short in the 5v reference line, which is shared with the APP and throttle sensors.
I did have time to unplug it before work. Still no throttle response
 

MRRSM

Lifetime VIP Supporter
When you replaced the ACC Pedal... Did you use either an ACDelco or Delphi OEM Replacement Part...or did you choose an Off Brand or After-market Component? This choice may make ALL of the difference in whether or not it works well with the PCM in a compatible way; given the sensitive nature of the Dual High-Low 5 Volt variances used to calculate Pedal Position accurately via Pulse Width Modulation (PWM) on the Class 2 Network.

Also... Chafed, Broken and Shorted wires hidden inside of Wire Bundles or in/near Metri-Pak Weather-Proof Plugs that connect up the The MAF Sensor, The Throttle Body and The ACC Pedal; all and sundry, if shorted or damaged can cause the PCM to place the Engine in Reduced Power Mode instantly if ANY of them suffer Poor Plug Connections or Broken or Sketchy Wiring.

Be suspicious ...Use a Bright Flashlight and a Light Touch when performing any "Push-Pull" Wire Harness and Plug Testing around the Engine. An inexpensive "Broken Wire Probe" Kit from Harbor Freight can be VERY useful in rapid, pin-point Broken Wire Tracing inside of harnesses as shown by Brian from Briansmobile1 using a less expensive variant in this Youtube Video:


...and here is another Video on the subject from Eric "O" over at South Main Auto discussing the "Power Probe" Variant of this Handy Tool:

 
Last edited:
OP
OP
L

Lifechanger

Member
Thanks about to watch the video! I haven't replaced the Acc pedal yet. I didnt want to untill I knew 100% that's what is was. I'm a farmer, money is tight lol. I plan on going through more wires today. I did see the I have to wires disconnected from what I believe is the pcm. I'm dealing with getting a new (used) cluster
 

budwich

Well-Known Member
the pedal sensor can be readily checked out with a meter before gambling with replacing. I doubt that it is the sensor. The two "dangling wires" doesn't sound right.
 

Mooseman

Moderator
A wire tap on anything from the PCM harness is not good. Download the manuals from the link in my signature and trace them. I'll bet it's the source of your troubles.
 

budwich

Well-Known Member
pull the connector and look to see if you can determine / trace which pin on the connector is going to the "pictured" wire. Might be tough but hopefully you can see where that wire shows up on the connector body. Once you have the pin number / connector number, you might be able to determine what it involves. You can also use the wire color to help determine which is which from a connector diagram.
 

Mooseman

Moderator

MRRSM

Lifetime VIP Supporter
Please view Post #4 in this Link and Download ALL of the PCM Wire-Pin-Out Diagrams of the GM P-10 PCM and the C1-C2-& C3 Plugs to PCM interfaces. The Blue Plastic Wire Connectors in plain view just below the White (Natural) Colored Connector shown in your Image appears to be some type of Non-OEM or After-Market wiring Add-On that is foreign to me.

If nothing else... knowing whether or not the vehicle is equipped with any Non-Factory Alarm or Remote Starter System and then getting online access to whatever Installation PDF Manuals were followed might give you an idea as to what that Clipped Off, Large caliber White Wire and both of those Blue Plastic Connectors happen to be functionally wired into:

 
Last edited:
OP
OP
L

Lifechanger

Member
I've been going through these diagrams Holy S#it... I got Wednesday and Thursday off hopefully that gives me enough time. Lol. Thanks yous guy have helped alot. I've severely underestimated this project. In my defense I've never used wiring diagrams before 😂🤣
 

MRRSM

Lifetime VIP Supporter
Your two best allies for understanding and explaining anything Electrical are @budwich and @coolasice. If anyone can offer some help and guidance in working through these issues... They can.

@Mooseman 's link to the GM Digital Manual provides you with One Half of the information with discreet Wiring Diagrams that correlate to those PCM Pin-Out Images... then it's just a matter of figuring out Which Connector hooks up to Which Colored Wire(s) Goes Where and Does What...and using the Alpha-Numeric Code unique to Each Wire makes it a fairly straightforward Diagnostic Process. ;>)
 

Maverick6587

Well-Known Member
@Lifechanger I highly suggest using that wire tracer from the video that MRRSM linked in the 7th post in this thread. I used a similar tracer for a fuel pump/5v reference issue I spent a week or two tracking down and it saved my life!

I'd be happy to walk you through understanding the wiring diagrams if you need help with that, just give me a call. Message me through conversations for my number. Otherwise good luck on the wire hunting.
 

MRRSM

Lifetime VIP Supporter
If you manage to locate any Wire Breaks and thus require new lengths of Automotive Grade Wire... This Auto Quality 20 GA AWG High Temperature Multi-Colored (10) Wire Set Bundle shown below are what you will need to Match the Colors if possible... then slip some Weather and Corrosion Resistant Sealant Type Heat Shrink Insulation Tubes on FIRST. You could also choose to use 18 AWG of the same Auto Wire Quality if you think a thicker set of Real Copper Wiring is called for.

As mentioned... Slide Weather Proof Heat Shrink Tubing Insulation sections of the appropriate lengths over the wires and slide them well away from the areas being repaired FIRST. Then Solder the Wire Splice attachments together with Silver Solder and follow up with using a Heat Gun to position the Heat Shrink Tubes back around each repair... and Melt the Sealant around each one until its "As Tight as Dick's Hat Band...".

There are shorter lengths of Auto Quality Wire Bundles available (10') displayed as alternative choice on that Link... but this particular one gives you an idea of what is required and has 25' Lengths that can come in VERY handy for many projects. Obviously... Whoever installed that Blue Plastic, After-Market Wiring in your vehicle...chose to use a lesser secure method for Cutting/Splicing the add-ons. Because the wire connections are going to and from the P-10 PCM... they deserve the more secure method of being Soldered; given the harsh Condition under the Hood:



88129
 
Last edited:

budwich

Well-Known Member
If you have some kind of "after market" / "DIY" wiring, then it costs nothing to temporarily remove the "quick splice" clip CAREFULLY (You can readily pick one up if you need to replace it). Then, this will give you a chance to inspect the wiring to see if it is broken at that point. Further, with that point exposed AND with the battery disconnected, you can use your meter (on resistance) with a probe at that point and with the other probe GENTLY / CAREFULLY test on the pcm connector which pin that wire is connected to. This should quickly help you find the right number on the pin which then will readily determine which circuit is involved.
 
Last edited:

coolasice

Well-Known Member
Looking at that picture of the harness, looks like the one of the taps in on the knock sensor 2 signal wire (lt-blue). I can't see the other wire color that the tap is on. Are there any other taps on the pcm harnesses? Vehicle history? Did you purchase it like this just recently?
 
OP
OP
L

Lifechanger

Member
Looking at that picture of the harness, looks like the one of the taps in on the knock sensor 2 signal wire (lt-blue). I can't see the other wire color that the tap is on. Are there any other taps on the pcm harnesses? Vehicle history? Did you purchase it like this just recently?
Yes just like this. I've had it for a week. I've done nothing except taken out the cluster replaced one of the wheels. The guy that had it before me didnt put alot of things back properly. So just been going through everything. I have to 10th and 11th off. So I'll be able to spend both days on this
 

Online statistics

Members online
8
Guests online
177
Total visitors
185

Forum statistics

Threads
19,203
Messages
576,513
Answered questions
1
Members
11,919
Latest member
Pepolleke
Top Bottom