Recently the car started idling at 1500rpms when it was warm. It also started to throw a code so I pull out my handy paperclip figuring I'll pull the code and figure out the problem.

Well I hook my pin up (A to B) to the ALDL, turn the ignition to on AND....nothing. The SES light comes on like it does when the car is about to start. Doesn't flash, the fans don't come on like they normally do in diagnostic mode or anything. I've run the codes before and it worked just fine. I also put a Voltmeter to it and while off was zero, when I turned the ignition on I got 5 Volts so I'm getting power at least lol.

Anyways, the idle thing is bothering me also, but more importantly, anyone have any ideas on how I go about diagnosing while the car won't go into diagnostic mode? Thanks for the help!

 

I dont know TPI that much or thirdgen ecm's but a high idle could be vacuum leak or a sticky throttle.

 

I thinking the vacuum leak might be the cause of the idle as well. I'm gonna slowly go through and check them. I know the throttle isn't stuck, checked that end already. Thanks for the input though

 

with the key off unplug the ECM & turn the key on & see if the check engine light is still on, if it is then you have a short somewhere, if it is off, turn the key off & plug the ECM back in & see if you can pull codes. if you can't odds are your ECM is bad. but before replacing it check all the grounds, from the battery to the motor, motor to body, battery to body, also check for good computer powers & grounds.
if everything checks good so far, odds are this won't do anything, but you can also unplug all the sensors & see if that lets you pull codes.
if you still can't pull codes pull the ECM out & try reseating the PROM or MEMCAL, i don't remember which one your car has.
if you still can't pull codes at this point then its time to try another ECM.

 

vacuum leaks can happen if the intake manifold gasket isn't sealing too