Pontiac Repair: Car wont start - intermittent, obd ii code reader, external circuits

Question
QUESTION: Hi,
I have a 1996 Gran Am with a 2.4L engine. In the morning, if the weather is damp, the engine will turn but the car will not start. By the time I get home at night, the car will start. What should I look for?


ANSWER: It could be a bunch of things.. does it start and stall? If so does the security lamp come on or flash? if so the factory anti theft is causing you an issue. In order for it to star tand run you need spark,fuel and compression I'm sure it has compression if it does indeed start and run. so either your missing spark or fuel. you can get a spark tester at the parts store and check for spark but you have to make sure the other plug wire is gounded on the coil that you are testing. There are 2 coils that run the 4 plugs. check the fuel pressure on this engine it's a pian because it doesn't have a pressure tap. you could have a temp sensor that's acting up telling the computer the engine is hotter or colder then it actually is. Has and service engine light come on? if so that could be a clue. Other than that you'll have to take it to a shop and let it sit overnight and have them check it out cold to see what's going on with it. Good luck :)


---------- FOLLOW-UP ----------

QUESTION: Hi Todd,

It does not start and then stall.
I bought an OBD II code reader. When I hooked it up, I got error code P0600. This told me that there was a Serial Communication Link Error. Like I said this only happens when the weather is damp in the morning. At night it starts. Is it the CPU module or do I have a cold joint somewhere. If so, where should I look.

Answer
Hey Frank:

I do not have access to any service info from home back any further than '98 and that code is not aplicable for that year car. but as a rule of thumb any 600 series dtc is an internal failure of a control unit and it usually doesn't involve any external circuits. It';s basically an internal watch dog for the computer I would say it's the computer is bad but like I said without a manual I can't say for sure. Also the ecm on that car has to be programmed to match the car this is to be done my either a a/c delco dealer or a gm dealer.. Good luck:)