P0157?

DareDog · October 2, 2020

2005 1500 5.3L 160k. Gotten this code. The O2 sensors are new in last 2 years. New Acdelco parts put on. Could i have a defective part? How to tell if sensor is actually bad? Or something else? Coolant temp sensor? Truck runs normally and no decrease in fuel economy.

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CamGTP · October 2, 2020

It won't change fuel mileage or running performance because it's the sensor after the cat converter.

The code says that it's possible there is a wiring issue with the sensor. Be it within the o2 sensor harness itself or with the wiring going down to the sensor.

If you want a free test that only takes your time you should flip flop the rear o2 sensors side to side. If the code changes to the Bank 1 sensor 2 fault, then you know that sensor is the cause. If the fault stays as a Bank 2 sensor 2 fault then you have issues with that side still.

DareDog · October 10, 2020

It won't change fuel mileage or running performance because it's the sensor after the cat converter.

The code says that it's possible there is a wiring issue with the sensor. Be it within the o2 sensor harness itself or with the wiring going down to the sensor.

If you want a free test that only takes your time you should flip flop the rear o2 sensors side to side. If the code changes to the Bank 1 sensor 2 fault, then you know that sensor is the cause. If the fault stays as a Bank 2 sensor 2 fault then you have issues with that side still.

Looked at it today. Took sensor out that is throwing the code. Last year put New sensor and put extender on it with also.. Well extender rotted out. Took it out with o2 sensor. Nothing is in there now. Drove it and CEL went off.

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DareDog · November 9, 2020

So now got P0158 code. Swapped o2 sensors. It did not change the code. So its not the sensor then. Researching online it could be ECM, fuel pressure regulator, coolant temperature sensor. Thinking now changing coolant temp sensor. with scan tool its reading 192F. Shouldnt it be 210F? Have not done anything and CEL went back off.

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CamGTP · November 9, 2020

The thermostat in that truck should be a 192 or 195 so that temp is normal. The cluster and real coolant temp are never the same, the gauge will always report higher than actual on those years.

I'd be looking at the harness now because both those codes are circuit codes.

Ian Mills · November 10, 2020

58 minutes ago, CamGTP said:

the gauge will always report higher than actual

How much higher? As in the gauge will show ~210 when it's actually ~195?

CamGTP · November 10, 2020

Yeah, pretty much.

The NBS and NNBS trucks are pretty well known for that. The gauge will be about 10-15 degrees over the actual temp in the engine. The later 2014-2018 trucks are a little more accurate but still off some. The newest trucks are much more spot on from everything I've seen.

Even the warm up temps are more off. Once it creeps past 160 degrees it's more like 120-130 degrees.

DareDog · November 21, 2020

The CEL now goes off on its own. Then will only come back on when truck is idling for over 4 minutes. Is it electrical? Some where in wiring?

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sefiroxx · November 21, 2020

Wiring heats up, expands, causing the cracked copper to separate. Try replacing the pigtail for the sensor.

DareDog · December 11, 2020

now its constant with cel code now. now getting p0158. High voltage in 02 sensor bank 2 sesnor 2. could it still be the wiring? going to check wire at some point.

sefiroxx · December 13, 2020

High voltage code is usually a short in the wiring, but sometimes in the sensor.

DareDog · December 27, 2020

How do i test the sensor? What setting on multi meter. I tested it and getting 0.

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CamGTP · December 28, 2020

O2 sensors run from 0-1000mv, a good multimeter will have a Millivolt setting.

A properly working rear o2 sensor will switch back and forth as the engine warms up and settle around 600-700ish mv if the cat converter is working correctly. A bad sensor will read near zero or really high off the charts all the time.