ECM repin accident, now wont fire, but have spark

[ghrarhg]

So I've been having what I thought was a ground issue. I tried to re-pin my grounds with a wire that I ran as a ground. I was popping pins out, and replacing them with the ground wire I ran.


Well, I got careless and accidentally put the ground to pin D13 in the ECM. That's the reference voltage to the DIS module.

I figure I popped the ECM.

What I've tried:

I got another ECM from the junk yard, no improvement. (I can't guarantee this one was good though)

Replaced the CPS no change.

What I've got.

1.) I've got spark. When cranking it is firing.

2.) It smells like I've got fuel, but it's not very strong.

What I don't have.

1.) In tunerpro the aldl data stream shows the engine RPM as 0 even during cranking.

According to the manual, I've tried trouble shooting a couple things, and it seems to point toward a bad ECM.

Does anyone have any ideas what else it could be? I can't make it to the junk yard for 2 weeks, so getting another ECM is going to be tough. I have a spare set of coils/icm that I could swap in, but it's a severe pain in my ass.

I don't see why it would be the coil pack since I grounded the ECM where it shouldn't have been, and the coil was essentially unplugged.

Does anyone have any ideas?

[ghrarhg]

Update:

Don't actually have fuel.

I was able to obtain another 7727, and nothing. Swapped out the ICM with one I had laying around and same result.

I've tried running through some of the diagnostic tests in the manual, but it keeps coming back to a bad ECM. I've tried 3 now with the same results. I can't believe that I would have grabbed 3 bad ECMs.

Anyone?

[IsaacHayes]

fried ICM?

[ghrarhg]

I'm thinking it's a possibility but i've already swapped it once...could be that the one that i swapped in was a dud.

I have a pretty basic test bench set up here, I may have to try it there and troubleshoot. It's amazing how frustrating a 5 second mistake can be.

[1988GTU]

you did check the fuses? theres one in the fuse panel and another going to the fuel pump relay.

[CNCguy]

Three bad ECMs seems unlikely.

Is Tunerpro correctly displaying other data like TPS, MAP, CTS etc?

If yes, it would seem that the ECM isn't getting the "reference" signal to know that the engine is spinning. I would think that there would be a simple way to check if there is a reference signal coming from the ICM. I know it can be checked with a scope but wonder if it would be possible to use a VOM to see if there is any signal when cranking.

Double check all the connections that you were working with. Especially the reference signal and its ground from terminals "E" & "F" on the five wire ICM connector since you are seeing 0 RPM.

[ghrarhg]

Yeah, I've checked all the fuses a half a dozen time hoping to find something, but once I realized the ECM was still getting power I gave up on that.

In the ALDL data stream, other things appear correct and are being updated, like O2 sensor stuff. I have my wideband logging through the ECM and I can see that change (+/- 0.01, not actual change like there's fuel being injected), so the ALDL output seems to be working. TPS also changes as I mess with the pedal, so I think the ECM is ok.

The ICM I swapped in was out of my junk yard 3400 that I used for parts. No guarantee that it wasn't junk too. I'll see if I can pick up a new ICM on my way home to make sure it's not that.

I'll see if I can get anything out of the multimeter for E&F once I get home.

Thanks for your suggestions,

Jon

[60dgrzbelow0]

Just a thought...But maybe the sensors for the cam and crank got FUBAR'd during the pin-scrambling event... due to voltage issues? Might be worth putting a Multi-Meter to work on them to see if they're all still nominal. (no sensors... no sensing)...??? In the unlikely event they went bad, then the PCM/ECM would never know when to "fuel and fire"...yes?

[ghrarhg]

I have replaced the crank sensor. I don't have a cam sensor (it's a gen 2 block). I'll have more info after tonight. I will be checking everything with the multi-meter.

Is there a list of all the sensor resistance values somewhere, as I'd like to check everything I can and go from there?

[60dgrzbelow0]

In the absence of a good list of diagnostic voltages for each sensor to check with a decent multimeter, it might be less aggravating to just get all new ones that seem to be involved. I know that the best scientific method would suggest only changing or testing one variable at a time, but when it comes to sensors, you could Mickey Mouse around trying to run down a hard to find problem with one or all of them, and in the end, it might just be better to change them all at once and eliminate them entirely as contributory to the problem. Trying to find a "One - Over -The World" listing for all OBDI-OBDII codes and high/low voltages for each and every sensor for each vehicle is like trying to find a pin...in a pin stack. Hopefully, the sensors to be replaced are not too expensive if you decide to use this idea.

Is it possible that you have a dormant short to the area of the ECM, perhaps a cut or a slice in a wire, or accidental mis-attachment of adjacent grounding wires that is only grounding the ECM in a way that happens only when the ignition key is turned to "on" and the circuit becomes live? You might want to throw in all new relevant fuses and circuit breakers in the process as well. I can't imagine that you would have run into three bad ECMs in a row...but people have been known to be struck by lightning more that once.

"Occam's Razor" suggests that "The simplest explanation of a problem/solution is almost always right...(99.999 % of the time)". So...If you re-trace your steps again, you are bound to find something simple that happened and then be able to fix the problem for good.

[ghrarhg]

I just got in from working on it, and I pulled every single fuse in the car, and checked it for continuity with a multimeter as well as visually to make sure it was not burnt. I replaced the ICM with a new one from Autozone. So that makes 3 total ICMs that have not caused it to fire. The original, the 3400, and the one from AZ. Again, it seems unlikely to me that all 3 ICMs would be bad especially the new one.

I know that Duralast is shit, but I figured it should at least work once. Again, the same issue. No RPM. Cranks and Cranks, but no RPM. I checked the 3 wire input to the coil pack from the CPS, and I'm getting around 1 volt when cranking. Does this seem like the proper voltage from the CPS?

I checked continuity between the 5 wires in the 6 pin connector and their respective pins in the ECM and everything checks out.

I thought that maybe the CPS wiring could have been hosed, so I took my CPS that I just replaced, with a spare 3 wire ICM plug I had laying around and connected the old CPS sensor close to the coil pack itself, and waved it around some steel thinking that it should at least register something...Nothing

I have checked the wiring, and the two wires that were accidentally swapped have been replaced. All the power supply wires are supplying power, and all the grounds are grounded. I'm just running out of ideas and things to replace...

I may start looking for a whole engine harness. What other sensors could be involved in the 0 RPM reading?

Thanks,

Jon

[CNCguy]

Jon,
I do not know what voltage the CPS would output but assumed the CPS was good since you stated that you had fire from the ignition coils.

The coils won't fire by moving the CPS near a piece of steel. The ICM has to receive the the proper 6+1 signal from the CPS or it will not fire. It looks for the six even pulses plus the odd one to know when to start the firing order.

I know of no other sensor that would make it read 0 rpm.

Are you using the same PROM each time you swap ECMs? I honestly don't know if a bad PROM would cause a 0 rpm reading or not. Just trying to think of what the common problem is when you swap ECMs and ICMs.

My money is on the wiring harness... either a bad wire, loose connection or a faulty ground. In your first post, you said that you were trying to resolve a possible ground issue. Did the car run before you started working on the harness? If so, perhaps there was a connector that wasn't fitting tight on a pin and by disconnecting/reconnecting, it is no longer making contact.

Maybe someone else will jump in with other suggestions. Electrical problems can be such a pain in the ass. I wish you the best of luck.

[ghrarhg]

The idea behind moving it past metal was that there was a diagnostic test that said put a test light between 12 power and the reference signal, pin E, on the six pin connector. If the ALDL stream shows any blip in RPM, the ICM is bad. Since that would only be a temporary power spike, i figure trying what I tried should produce the same results if the ICM was not faulty.

I have a total of 4 proms, and 1 chip adapter w/ostrich. I've tried each of the chips by themselves, as well as some of them in the adapter with the ostrich and still no change. I've also tried the variety of chips in each ECM.

I had my car running for a few weeks before the accident. I did a top end swap over the winter and only had it running for that short period since.

I will continue to check the wiring harness.

Thanks again for all your suggestions.

Jon

[60dgrzbelow0]

I know you've probably done this already (probably two or three times) but at the risk of having you take a swing at my chin for suggesting the obvious, have you tried methodically unplugging and re-plugging firmly each and every single wiring harness connector, starting at the ECM and working your way down the length of the entire harness to each and every sensor? But really... I'm with CNCguy... the problem just HAS to be either with a bad/ungrounded Crank Position Sensor ...or the wires/harness-matrix connectors between it and the PCM is scrabnoid. The Crankshaft Position Sensor is usually the final arbiter in determining engine RPM, regardless of make/model of engine.... so... What else can it be? Careful "finger-feeling"of the entire wires along their length (even pulling lightly on where they attach each connector); then cleaning all the ground connector/engine block/firewall locations with Brake Cleaner and re-tightening them along with putting in yet another new CPS might just break the evil spell the engine is under.

[60dgrzbelow0]

Mismatch on Plugging in ICM Harness...?

I just had a thought...You might take a look at this attached diagram (For the F-Body Carline Series...but perhaps similar for yours, too?) and see if on your engine it might be possible to swap some of the ICM connectors...I looked at mine and I could make this mistake very easily.