[Dave K]

P2097 has me all confused. I have struggled for years to get it straight what the code means. This is what I -think- it means based on reading the factory repair manual. Please fix my conceptual error…

P2097 indicates that the ECM is demanding too much fuel injected due to too much oxygen in exhaust after the catalytic converter. It has exceeded the threshold for LTFT multiple times. Something isn’t quite right with the engine, therefore throw the code.

That statement is more or less the opposite of what I thought it meant for a couple of years now. So do I get it now or am I still jacked up?

 

[bboaze]

Maybe your oxygen sensors are reporting incorrect exhaust gas temps.

 

[MikeBCo]

The code just means the mixture is too rich. Look for exhaust leaks, O2 sensor wiring, and observe both O2 sensors output. upstream should move up and down from0.1 to 0.9 (or thereabouts), while the downstream should be fairly steady and somewhat in the mid range of the upstream. Tap on the cat with a rubber mallet. does it rattle?

 

[Dave K]

The code just means the mixture is too rich. Look for exhaust leaks, O2 sensor wiring, and observe both O2 sensors output. upstream should move up and down from0.1 to 0.9 (or thereabouts), while the downstream should be fairly steady and somewhat in the mid range of the upstream. Tap on the cat with a rubber mallet. does it rattle?

Thanks for the reply. Your statement is my confusion. Does it mean the mix is actually sensed as rich or does it mean the ECM is trying to make it too rich?

 

[MikeBCo]

It is being sensed as too rich by the O2 sensors

 

[Dave K]

It is being sensed as too rich by the O2 sensors

That had been my understanding. Until I looked at possible causes from the factory repair manual:

exhaust leaks
vacuum leaks
missing engine air filter
low fuel system pressure
bad gas
lean fuel injectors

All of that points in the opposite direction- too much air, not enough gas. I also read on the web that GM uses the DTC differently than other manufacturers. Again, I feel confused as your statement is what I have read generically about P2097.

 

[MikeBCo]

I don't have any Volt specific insight to that code, just the usual Google research. How does the output from the O2 sensors look?

 

[Dave K]

I don't have any Volt specific insight to that code, just the usual Google research. How does the output from the O2 sensors look?

I have a voltage I can check on the scan tool. Not sure if i need to see it graphed or if a digital indication works, as in it changes rapidly. Any particular driving condition to check? Most of my ICE drivig is interstate, 80 mph.

 

[MikeBCo]

seeing a digital readout can lead you to bad conclusions potentially if the scan tool does not update the data frequently. Many update too slowly to be a useful diagnostic tool.

Generally, you would look for the upstream sensor to vary from 0.1 to 0.9V and back over a few seconds. The downstream should be around 0.4 or 0.6 and vary slightly, but generally be fairly stable. If the downstream bounces around similar to the upstream, that is usually the sign of a dead cat. The car must be in closed loop control after the car has warmed up to full operating temperature.

Here is a good picture found at: https://community.cartalk.com/t/bad-o2-sensor-or-cat-problem/167895 (see the second post). Not sure if the photo is copyrighted, so I am giving credit to where I found it. I cannot vouch for the discussion contained therein...