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1999 Chevy Cavalier no communication with scanner.
As mentioned in the title, I have no communication with my scanner. The scanner works on another vehicle so It's not the scanner. I have good power and grounds to the DLC. I only have about 18 millivolts at the DLC on pin 2 which is the serial data line to the PCM for communication and 18 millivolts at the computer itself. It should be around 7 volts. Here is what I have done so far and if there is something that I missed or should do next.
1. Disconnected the connector at the PCM and placed a test light at the DLC with one pin at pin 4 and the other at pin 2. I used my power probe on the disconnected connector at the PCM and put power to that circuit and the light lit up bright so no open or short in that communication line.
2. I checked all power and grounds to the PCM and they were all good.
3. I also voltage drop tested the ground wires for the computer where they bolt to one of the transaxle bolts and got 2.2 mv and I also checked the case of the transaxle and it had the same 2.2 mv.
4. All tests were done with key on, engine off.
So, are there any other tests that I need to do to condemn the PCM? Thanks.
Well, it turns out that my scanner is the problem on this car even though it works on other cars. It's an Otofix D1 that has worked on this car in the past and now for some reason it no longer does. I tried my Innova 5610 and Thinktool Pros on it and they both could communicate.
I did find in service data that there is not any voltage on the class 2 data line unless the scanner is trying to talk to the PCM so my voltage measurements with just key on, engine off with the scanner not hooked up were not valid. At least it seems like I don't need a computer for that problem anyway.
This car still has the intermittent long crank that I posted about a year ago. I've been hoping that the car would just break so that maybe we can figure it out.
