4cefed

Man, what a classic lesson in fundamental troubleshooting.
ECM failed, crank but no start. No fuel pressure, no spark, no check engine light.
Sent the ECM to get checked/fixed. They found some ic drivers that were toast. I get it back and install it in the car and it doesn't cure the problem. Same syptoms. Send the chip out, nothing wrong with the chip.

Get a friend to let me borrow his tech 1 and I start from the beginning with a complete system check. First chart tells me to check the fusable link that connects to the + battery cable. I do that it checks out fine. Then it wants me to pull connector b from the computer and check pin 10 and 11 (one is the circuit I just checked, the other is circuit 239 which is the ignition feed from the ECM. The test tells me to ground a test light and check each circuit. 239 does not light up and therefore I have an open in that circuit.

What is in that circuit? The SIR (DERM) module and the ECM fuse and the air bag fuse. Pull both fuses and the ECM fuse is bad. CHange the fuse and that bad *** 415 fired right up. It sounded REALLY good after a really bad week.
I love how these cars can just make you happy inside.

Now to get her cleaned up and ready for the spring.

xlr8nflorida

Nice

-=Jeff=-

What caused the issues with the ECM though?

FU

There ya go

flyboybob

it sure feels great when everthing works after all the frustration is over.

Vette Daddy

Congrats! I am not looking forward to trying to stat the 88 in a couple of months.

4cefed

Good question and one that I have been trying to get to the bottom of.
1. I am going to check all of the ecm pin grounds to make sure they are still good.
2. My chip has had a problem in the past and have a new chip in it right now.
3. my ecm mount was broken when I first looked at the ecm, might of had some shock damage?
4. and this is the one that is probably correct..........I burned out the ic drivers checking the fuel pump circuit with a test light (ouch, I know, not the smartest thing I have done with a car) and the ECM fuse just failed with old age because it doesn't look burnt, just looks like the element is broken.

4cefed

Threw the 3amp fuses in the car and took off for a shake down. I was expecting the fuse to blow again and it did. Car drove great in normal mode but when I opened the throttle with the full power switch on it immediately blew the 3 amp fuse. It might of done it if I floored it in normal mode. Looks like I have a short. I don't think a bad ground would cause that but I am going to check all of the ECM pin grounds.

LT5corsa

Can we see pictures of that "Biatch"?




David

tomtom72

Hi Joel,

not trying to stick my nose in but be careful when using anything like a test light blade to probe the female ECM plugs. One of our west coast members was doing that and the thickness of the test light probe opened up the female sockets in the ECM plugs. The result was intermittent contact because the ECM pins no longer were tight in the harness plugs, even with them fully seated. He ended up repining all four ECM harness connectors.


Tom

cadillac531

Did you check all the wiring for the SIR? It may be a wire coming up into the steering wheel for the air bag that has some insulation stripped away and is contacting some metal or another wire.

I had that happen to me with a 95 Suburban. Hit a big bump or jostle the vehicle in any way and it would blow a fuse. Turned out to be a wire coming through the dash into the wheel had some bare wire exposed.

Hope you get 'er all sorted out.

Constantine

4cefed

Sounds like good advice.

4cefed

I think I have a bad ignition module or ignition module wiring harness short. Circuit 239 (with the 3 amp fuse blowing) is the ignition feed signal from the ECM which gets it from the ignition module ignition feed output signal.

Going to check a few things out this weekend. I was also going to check the wiring you mentioned becasue SIR is in the circuit that is blowing.

Seems to run better when the engine is cold. Doesn't blow the fuse unless I floor it and let off (engine rotates in mounts slightly). After the engine gets hot fuse blows with little throttle input.
The first makes me think it is a wiring short and the second makes me think the ignition module is bad.

I will find it, pain in the ***, that's for sure.

When the fuse is in and the car is running it runs great with no codes.

8388

Hi Joel. Almost sounds like a wire between the firewall/engine bay and the engine may be making intermittent contact when the engine torques up. Have you checked all the wires that run under the ECM?

4cefed

With the engine running I have wiggled all harnesses from the fuse panel to the ECM without it blowing the fuse one time.

Wide_One

I'm sure you probably already done this but I remember from clutch replacement that there is a lot of wiring in the area of the throws from both accelerator, clutch and brake areas. Maybe a visual full stroking of all may be in order both running and off.