Throwing p0137 p0157 CEL codes during heavy acceleration only

[DeplorableACE]

So I bought a 2000 GMC Sierra 5.3l auto 4x4. 173k miles.

 

The first night I drove it home after buying it, the CEL came on after flooring the gas pedal. I check the codes and they are p0137 and p0157. "Low voltage" for "bank 1 sensor 2" and "bank 2 sensor 2" O2 sensors. So naturally the first thing I do is replace both downstream o2 sensors. No difference. CEL still lights up if you step into it a bit.

 

CEL will go away on its own after a period of time of normal driving, but will come right back if you give it 3/4 throttle or more a few times. Truck runs great as far as I can tell, doesn't seem to affect driveability. Not getting any other codes, just the p0137 and p0157.

 

Any ideas? The CEL is very annoying, and I want to get this problem fixed. Otherwise the truck is in great shape and I'm really happy with it.

 

Edited January 14, 2020 by DeplorableACE

[sefiroxx]

Run a scanner to see what the voltages are coming in. If at 0, then likely a wire problem.

[davester]

Even if not zero, I'd look over the wiring and connections, starting at the O2 sensor and working forward.  The engine rotating slightly from the extra torque when hitting the go pedal might cause the relevant wire to touch metal when it normally doesn't...

[DeplorableACE]

I took the truck to a local shop, and the tech told me their diagnostic machine couldn't find any problems. He wanted to install oem downstream sensors, also suggested installing a new MAF even though the current one appeared to be in spec according to the machine. Those seem more like blind guesses and firing up the parts cannon instead of troubleshooting. The chances of both the old sensors and the new sensors ALL being bad is very small. Something else is causing it.

 

I asked him if they checked the wiring harness, and he told me their diag machine says the sensors are getting power. Also said fuel pressure at the rail appeared be in spec.

 

If anyone knows someone in Denver that knows these trucks and can do some diagnostic work for a reasonable fee...

Edited January 17, 2020 by DeplorableACE

[swathdiver]

On 1/14/2020 at 2:59 PM, DeplorableACE said:

The first night I drove it home after buying it, the CEL came on after flooring the gas pedal. I check the codes and they are p0137 and p0157. "Low voltage" for "bank 1 sensor 2" and "bank 2 sensor 2" O2 sensors. So naturally the first thing I do is replace both downstream o2 sensors. No difference. CEL still lights up if you step into it a bit.

Get your battery checked out regardless of its age.

[DeplorableACE]

29 minutes ago, swathdiver said:

Get your battery checked out regardless of its age.

Thanks for the tip. You mean from a battery health tester that you'd find at a parts store?

[swathdiver]

54 minutes ago, DeplorableACE said:

Thanks for the tip. You mean from a battery health tester that you'd find at a parts store?

Maybe, I'm referring to a dealer level tool that can run the battery though its paces to identify it's ability to hold a charge and whether or not it has a bad cell.  Some auto parts stores will test for free and this is usually fine if the person knows how to operate the tool; many do not.

[Jojoman]

Did you ever figure out the problem? 
I’m having the same issue 

[davester]

...4 year old thread, and Deplorable (the o.p.) hasn't logged onto the site since around then, you are pretty unlikely to get a response from that user.