More on the P0174 Code.....

**jfl330** · 06-05-2012, 11:44 AM

I decided to watch the O2 sensors with key on, engine off. 3 out of 4 behaved identically with the problem one showing 0 mV almost immediately. This showed it's either a O2 sensor, the wire harness, or the PCM. I swapped O2 sensors with one that behaved normally and it too showed 0 mV almost immediately.

So, its down to either the harness or PCM.

Will remove the PCM and test the harness soon.

Jon

**cammed goat** · 06-05-2012, 11:48 AM

Test the harness first. Could be a connector that has expanded over time, causing a loose connection.

**jfl330** · 06-05-2012, 12:28 PM

Originally Posted by cammed goat

Test the harness first. Could be a connector that has expanded over time, causing a loose connection.

Absolutely!

Jon

**NaviDyn** · 06-09-2012, 06:12 AM

I haven't been here in a while, and this looks like a comanion thread to another problem since you said more on the P0174. Is that correct?

Is there a GM schematic online? With the key on and engine off, there shouldn't be voltaged produced because there is no potential difference between the manifold and sample in the sensor. Any voltage should be for the heater through a fuse, which is why I ask if there is a diagram. You guys problably know already from memory what the circuit looks like. What are the 3 identicall ones doing?