After doing a pretty extensive search of past topics and responses, I've not yet come across the answer to my problem.

The car is an 89 TA GTA 350 auto with the following mods: cat back exhaust, TB coolant by-pass, and is doing the following:

Here's everything that I've tested. I DVM'ed the O2 wire at the sensor and came up with 1.08V at idle. I figured that couldn't be right so I checked it at the ECM and got the same voltage. Step 2 involved DVM'ing the actual O2 sensor and got the normal voltage from it starting at cool idle was .03~ volts and rising the longer it was idling. The O2 sensor reading is accurate, but the ECM is not receiving this voltage reference. It is stuck at 1.08V leading me to believe that either the wire is toast or the ECm is toast. If there are any other options please let me know. The car is stalling when being driven around town and it will not idle when warm at all. Obviously because of the voltage at he ECM it is running rich, yet no code 43 is being set or triggered by the ECM.

I'm quite confused by this situation, and can't quite figure out what to check next.

The TPS voltage is within spec at idle and the base timing is ~8* at idle. Any help would be appreciated. Thanks

 

Any ideas anyone?

 

V6, have you checked the O2 sensor ground wire at the ECM? It's tan and it's right next to the purple O2 sensor wire.

With one probe of your multimeter (set on ohm check) directly on the (-) battery terminal, you should see less than two ohms.

 

Unplug the O2 sensor and measure the voltage on the ECM side. It should read 450mV (or .45 V). If it does not read 450 mV (give or take a few mV) then the problem is the ECM side of the circuit, wether it be the ECM itself, or like others mentioned, possibly a ground issue. If it does read 450, then I would be leaning towards the O2 sensor itself. How new is the sensor you have?

What are the chances that you are really running rich and the O2 sensor is just doing its job? Maybe you have a leaking injector dumping fuel? Just a thought.

 

I know which wire you are talking about, it was the object of my attention a while ago. It had been pulled out of the body harness that runs behind the engine and cut. Since this is obviously not the way it was installed, I used a butt connector and reattatched them. I'll have to test it for resistance, I don't think we did that. where should I probe at? The ecm or where it goes through the body harness? If the resistace is more than 2ohms, due to the connectors, what happens?

The wire going from the O2 to the ecm is reading 1.080V steadily, wheather the O2 is plugged in or not, engine running or not. The O2 is less than a year old, who knows, the old one may have been ok. Its like the ecm is sending out 1.080V all the time. If that is the problem, would a different prom be neccessary? Or the whole ecm? I don't know a lot about the ecm to know what would need to be changed.

Always possible I suppose, but I did change injectors. I'll test the voltage when the engine is hot to see what it's seeing.

Thanks for the info guys, I'll let you know what happens.

 

Unplug the ECM connector and then check the tan wire. That way, your multi-meter is seeing what the ECM sees.