Codes P0137, P0157, P0171 and P0174 P129f, the engine cranks but does not start?

CWARD1450

MEMBER
2020 GMC SIERRA
5.3L
V8
4WD
AUTOMATIC
80,000 MILES

I got home from work one afternoon. The truck was running fine. 30 minutes later I went to leave, and the truck would not start. As I kept messing with it, it eventually started but was sputtering and shut off. Vehicle no longer starts, and I have the following codes.

P0137
P0157
P0171
P0174
P129f.

Where do I begin in trying to fix the issue when the vehicle will not start?

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
47,186 POSTS

We need to see if the problem is fuel or spark related, this is the code that starts things off and causes the additional codes, P129F

P0137: O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
P0157: O2 Sensor Circuit Low Voltage (Bank 2, Sensor 2)
P0171: System Too Lean (Bank 1)
P0174: System Too Lean (Bank 2)
P129F: This is a manufacturer-specific code, and for GMC, it often points to an issue with the fuel system,

So, if the high- or low-pressure fuel pump starts to go out it will cause these codes and when it fails completely the engine will not start anymore.

I would use starting fluid to see if the engine will run which can help confirm it is a fuel issue. Please go over this video to see how:

https://youtu.be/lXLJbuAZ4CE?si=Y1VaJpos0Qy4KLtH

If the engine runs on starting fluid and you turn the ignition system on and hear the fuel pump in the tank run for about 5 seconds, I have seen the high-pressure fuel pump goes out or the camshaft lobe is worn down. When the pump is out, I would use a flashing to check the camshaft lobe condition. Here is how the job is done, clear the code once completed. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.

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