TPI ignition trouble
 

Hey guys, got a bit of a problem. My car stalled out in traffic about two weeks ago and would start up after it cooled down. Turned out to be the ignition module. Fixed that and then while test driving with the new module the car stalled out again and now will crank but won't catch due to no spark. It seems like whatever caused the ICM to die in the first place konked out from the resistance of the new ICM. I tested the new ICM since the final stall out and it is fine. So far I have replaced plugs, cap and rotor, external coil and I've removed the starter and had it tested for shorts and I'm getting nothing. After clearing the codes by removing the negative cable, I still have an SES light on making me think that my ECM might be to blame. I don't own a DVM and I don't really want to invest in one just to find out this whole mess was just something stupid. I haven't touched the distributor besides the cap and rotor and the ignition module. The distributor is also new as of last year. Anybody ever had similar issues?

If you don't want to invest in the needed tools I would reccomend getting the car to a shop to be checked out by someone that has the correct equipment and knowledge to diagnose such a problem. Anything someone tells you will be useless if you have no way of checking the system other than by swapping parts.

theres a way to read the codes with a paper clip on 3rd gens... i forget how, since i bought a scanner lol

Yeah, just jump the ALDL and count the SES lights.
Check the ESC. It sits behind the fuel pump and maf relays on the driver side fire wall. I replaced my ESC and ICM, cured any stalling and sputtering problems I had.

http://www.chevythunder.com/aldl_terminal_id.jpg

Trouble code retrieval
With the engine not running, key in the "on" position, jumper terminals "A' and "B". With the ecm in the diagnostic mode, it will first flash a code 12, indicating the ecm has entered this mode. You will see the SES do this for a code 12: flash, pause, flash, flash. Think of it in on/off state: 1, pause, 1+1 = 1+2, or 12. It will flash this code three times, then there will be a short pause, and it will flash code 12 again three times, as long as there are no trouble codes, the ecm will flash this over and over until the jumper is removed from the ALDL.
If there are trouble codes stored, it will follow the code 12, starting with the least numerical code first, flash it three times, go to the next numerical code, flash it three times, and so on until it has reached the last code. Then it will flash code 12 again, and start the whole process again, until the jumper is removed. This will give you plenty of time to retrieve the codes, and double check yourself to make sure you have written down the right ones. Example: Code 34: flash, flash, flash, pause, flash, flash, flash, flash. (1+1+1, pause, 1+1+1+1= 3+4, or 34.
Below is a list of trouble codes:
12 ecm diagnostic mode
36 maf burn-off malfunction
13 oxygen sensor
41 ecm tach signal failure
14 cst voltage low
42 est failure
15 cst voltage high
43 esc (knock sensor)
21 tps voltage high
44 lean exhaust
22 tps voltage low
45 rich exhaust
23 mat voltage high
51 prom failure or installation
24 vss
52 calpak missing
25 mat voltage low
53 high battery voltage
32 egr system malfunction
54 low fuel pump voltage
33 maf or map reading high
55 defective ecm
34 maf or map reading low
61 Oxygen sensor
35 idle speed error

I already pulled codes, I only have a code 23 (IAT, TPS) but this shouldn't be causing my car to have no spark at all. What I meant with the SES light is that I don't think it should be on at all because I had the car disconnected from the battery for over 15 minutes and this should have cleared all codes and the SES light shouldn't be on anymore but it is and when I pull codes now it only throws me the code 12. Is this a sign of my ECM being damaged?

when running, if the ses light is on and the ecm only puts out a code 12, then something is def wrong, possibly some wiring shorting, or yes, the ecm could be bad. a code 12 only means everything is functional.

what year/motor is your car, ill let you know what ecms are compatible if you wanna try to find a used one to swap and test it.

Its a 91 305 TPI, I gave up and took the car to a shop today, I've been working on this for the past three weeks. J Larue, in Princeton. Shop owner there owns an 88 C4 and a ZR-1 and so does his wife. I think I'm in good hands.

ok thats fine. let us know how it turns out.

and yea, u have a "730" ecm, same as 90-92 tpi cars and 3.1l v6 cars.

Fixed: One of the wires connecting to the coil had burnt through its coating and wasn't carrying any voltage, easy fix. Don't know how I missed this when I replaced the coil. Glad it wasn't my ECM, would've been the second one in a year.

Glad to hear that you got it back together and it was just something simple.

- Justin