Codes P1275, P1635, REP, and SES

Tiny
VIKKI MARIE2
  • MEMBER
  • 2002 GMC ENVOY
  • 4.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 183,000 MILES
Just installed a new fuel pump, now there's no throttle response when I push down the pedal. Starts and idles fine. But pump the gas, , othing. I've replaced the APP sensor (only to find out the old one was fine) as is the new one. Had an electrician come hook up to it, told me to check multiple wires. Specifically the ones to the TB and the APP. Both getting 5v. The wires on the ECU for the TB/APP are also getting 5v. So why am I getting these codes? And why doesn't the engine rev when I hit the gas? The Reduced Engine Power light is on, as well as the Service Engine Soon light, and it's throwing codes P1275 and P1635 Going crazy, please help. TIA
Sunday, January 10th, 2021 AT 12:06 PM

4 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Unfortunately the only way we are going to know what the issue is on this is to run through these tests and find out what we have for each step.

The thing that is concerning about what he found was that he said it was 5 volts. This will set this code if the voltage is greater then 4.87 volts. I understand if he was rounding up but we need to be accurate on this type of testing.

Here is a guide that should help with this type of testing?

https://www.2carpros.com/articles/how-to-check-wiring

Let us know what questions you have and we can go from there. Thanks
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Monday, January 11th, 2021 AT 4:03 PM
Tiny
VIKKI MARIE2
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Okay, so I am thinking this maybe where my problem is. Because I'm getting 5.05v on all 4 wires. The 2 relative to the TB and the 2 for the APP. So if that's the issue, how do I fix that?
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Wednesday, January 13th, 2021 AT 7:04 PM
Tiny
VIKKI MARIE2
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  • 3 POSTS
Okay, so scratch that. I think the volts I'm getting is correct. The 4.87v your referring to is on the signal wire. Which is where it should be. I think I have a bad ground somewhere. But I can't find any diagrams to tell me where to look.
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Thursday, January 14th, 2021 AT 11:54 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I am not so sure this is a ground issue because that is not how the 5 volt system works. The control module grounds these circuits so there is not a traditional ground. I included the wiring diagram for the APP sensor. You will see the 5 volt reference wires and the signal wires. If you have 5 volts on the signal wires then that means the PCM is being told that the accelerator is at wide open.

So you should have just under 5 volts on the 5 volt reference wires and then the low reference is the difference between between that and 5 volts. So if you have 4.87 volts on the 5 volt wires then the low reference would be 0.13 volts. The signal wire is going to vary in voltage from.5 volts to 4.5 volts depending on how far the pedal is depressed. Does that make sense? If so, we really need to go through that testing from the last post and see what we turn up.
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Thursday, January 14th, 2021 AT 8:06 PM

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