I spent a good part of today working on a '96 Grand Am w/ a 2.4L. Original complaint was really rough idling and driving, black soot shooting out of tailpipes, poor milage, and occasional lack of response to throttle. It had 2 DTC's; one for the downstream O2 sensor and one for a random misfire.Owner didn't recall whether O2 was lean, rich, or not responding. Plus were completely fouled with carbon, as was the tip of the O2 sensor. O2 tested bad with my inexpensive sensor tester. She also was running w/out an air filter and the throttle body was really thick black carbon. Replaced plugs, O2, air filter, and cleaned the throttle body as well as I could w/out removing it. Re-connected battery that I had disconnected to clear codes and started it up. Idle was smoother (after all the cleaner burned off), throttle response was more precise but it still wasn't "right". I took it to Auto Zone to check the codes and had two new ones: bank one too rich; and the killer; "PCM has determined that a malfunction exists in the serial communication link between the PCM and other modules in the system". On the drive back the ABS light came on for several minutes, then went out and then the seatbelt light did the same thing. Also, there was still a code for the downstream O2;"insufficient activity for current operating conditions" Tomorrow I plan to check all grounds and relevent connections, but if anyone out there has some experience with this or similar problems, I can use all the help I can get. It's so much harder when you can't link to the PCM and see what's actually going on; nor can I read or clear codes. Can't you do that by disconnecting the battery in a '96, or do you need the tool? Thanks in advance to anyone who can help with this... Chip
- posted
18 years ago