robertmee said:
That's not odd...that's what I was saying. The message is ultimately driven by the sensor. Not the position of the gauge. What I meant by that is there isn't some internal wiper on the servo that based on needle position turns on a light or message. So we're on the same page. I maybe wasn't clear enough in the brevity of my message
Yes, I got that, the light is not generated by the physical needle position. But there's a 50% chance that is approximately what is happening -- at least on a 2004 model.
Let me explain: I hooked up my Tech2 to my 2004. I have 3 different oil pressure readings. From the PCM, I get the actual raw data -- a voltage reading (1.67v at idle). From the IPC, I get interpreted values of 244 kpa measured, and 248kpa displayed. In other words, there
is a feedback circuit on the needle movement.
So which one triggers the warning display? I personally would pick the PCM signal, but who knows what the GM engineers were thinking sometimes, they might have linked the warning to the feedback circuit.
Now, that's with a 2004, which is all I have here to check. The 2004 uses a 3-wire sensor connected to the PCM. Looking at the schematics I downloaded for the 2002 model, the system shown is somewhat different. Schematics show a single-wire sensor connected directly to the IPC. I don't know if there is a feedback on the 2002 gauge or not.
All that said, I don't know which system he has, because the damn FSM shows
both types in the 2002 component locators! Mid-year change? Error in the FSM? Who knows, but the engine component locator shows a 3-wire sensor at the back of the engine (same as my 04):
And the IPC component locator shows a 1 wire sensor under the intake manifold between cylinders 5 and 7:
This is certainly the sensor that matches the 2002 schematic, but I think the OP would have mentioned it if he had to remove the intake manifold to access the sensor!
So I'm really curious now: acedown13, do you have a 3 wire sensor or a 1 wire sensor, and where is it located?