Problem with 2 bar MAP

[Jim Blackwood]

I've attached a datalog, P01 controller, '02 Camaro 2 bar OS. The trace numbers for MAP match the PID numbers. What is strange is that the reading when cranking is up around 195 kPa, which makes the injectors go way rich. I then unplugged the fuel pump relay (note the MAP reading did not drop while doing this) which then allowed the engine to start long enough to burn off the fuel in the intakes, with the MAP dropping to a low of about 55 then coming back up to about 130 as the engine died. Why it didn't return to 195 I don't understand either.

Has anybody seen something like this before? I unplugged the MAP and then the engine will crank up easily and I think if it were warmed up it might continue to run.

I looked at the MAP settings and they are around 210 with an offset of 10.

Any suggestions? I'll check the wiring tomorrow.

Jim

[5FDP]

Possible the 2 bar MAP you have is bad or the linear and offset data is wrong for the MAP you are using.

[Jim Blackwood]

It does appear to be a MAP sensor issue. Looks like I was shipped a 1 bar instead of a 2 bar. I swapped in a 2 bar and the values came down to half and the car starts.

So here is my question: What 2 bar sensor is properly matched to the '02 Camaro 2 bar OS? The two that I have tried are 12615136 (Camaro) and 16235939 (GMC). I would prefer to use the right sensor rather than recalibrate. Photo below.

Presently the MAP sensor reads 65.8 kPa at rest which can't be right. I'm at 600 ft above sea level so it should be reading about 99.

Jim

[5FDP]

A lot of people run the cobalt 2 bar sensor but I don't have the part number for it.

You can run a 3 bar sensor too, many use the ZR1/CTSV 3 bar MAP sensor. Just swap two pins on the connector and plug in the new linear and offset data.

[Jim Blackwood]

Maybe it would be better to change the calibration to match the 2 bar sensor that the '02 Camaro used and buy a new one. The number I have should be right I think but I'm sure I can confirm that. (12615136)

So where do I find the settings that I need to change? I know where the range and offset settings are but apparently they have little or nothing to do with conversion from 1-5v into 0-210kPa.

Jim

[5FDP]

The camaro in those years never ran a 2 bar sensor. It just automatically changes the linear and offset settings to generic 2 bar settings when the 2 bar OS is applied.

The 12615136 MAP sensor should be 200/10.33 for the linear/offset settings.

There is nothing else to change for the MAP sensor past that. Make sure to remove the 1 bar map sensor channel in the log and replace it with the 2 bar map sensor channel. If the readings in the log are still off then I'd say it's a sensor problem.

[Jim Blackwood]

Thanks. The MAP settings are right. I ordered a new ACDelco sensor, the 12615136 was apparently superceded by ACDelco # 213-1631 which is the same one used in the '05-'07 Cobalt. In the meantime I installed a Chinese sensor and it seems to be reading correctly for now.

The PID channels seem a bit off. I was using the only one that is labeled as a 2 bar. It read zero at KOEO and about 65 after the engine died. I enabled the MAP voltage and SAE MAP channel and had proper readings there, so switched in the SAE channel, but here's another issue. (Presumably with the scanner or the OS) After selecting the SAE channel the dialog popped up asking if I wanted to use the SAE channel. (?) When I selected 'yes' it didn't give an output at KOEO. I didn't test to see what it did after starting. I went back and selected the SAE channel again, told the box 'no, don't bother me' and then it worked correctly. MAP reading is now 99kPa at KOEO which is exactly what it should be at my altitude.

I will test again when the Delco part comes in, and do a pressure test as well to confirm the upper end of the scale. Thanks for the help.

Jim

It seems the Chinese sensor failed in such a way that it began to output very much like a 1 bar sensor but the bottom of the scale seems to be off. That's the only thing that explains why I was able to tune and then suddenly I was not. So... Buy genuine parts.