Code 43 and No Start Condition

[jmgtp]

Seems like the electronics on both my vehicles hate me now!

Last night I was driving and car had a violent buck but for only a split second (felt the same as if you hit the rev limiter - I suppose only 5 speed folks could relate to that). Then a minute later I was stopped at a light, when I went to go as I let the clutch out it stalled. I restarted and tried again and the car shook violently but I managed to get it to a side road. Busted out the paper clip: codes 34 and 43 = Map sensor and Knock Circuit. A minute later I tried to start again, it started moved 5 feet stalled out and would not start again. I replaced map today and reset computer. Now there are no codes but also no start. There is NO spark. Replaced Ignition module and all 3 coils with a set that I know is good. Still no start. The manual I have says code 43 = KS. So if there was NO knock signal (like the wire was unplugged or broke) would that cause a no start? I'm about to get under the car and with the ignition on check for voltage at the KS harness. Also, if I does anyone happen to know what the resistance should read between ground and the output of the KS? Any other ideas?

Now I have two 60* V6, one hardly runs and the reliable one now doesnt run!! aaghhh! Dammit! someone send some good luck my way please!

[jmgtp]

At the ICM I measured the crank signal voltage (theres 2 two-wire harnesses and I did not know which on was for crank signal so I measured both). The harness by the 2/5 coil measured 12volts with the key on and not cranking and went down to 8 volts while cranking. The two-wire harness next to the 1/4 coil had no voltage at all, while cranking or key on, so I imagine that one must be the crank signal harness and its getting no signal. So, I must either have bad wiring, a bad crank sensor, or *heavens no* a worn thrust bearing allowing the CPS to come out of alignment and hence no signal. So I guess my next question is... even if the CPS was out of alignment with the reluctor wheel on the crank would there still be some voltage so long as the ignition was on? If so, that would prolly mean bad wiring or bad CPS and an OK thrust bearing. I imagine as whatever failed, wiring, sensor or bearing went out it happened over a small time span (maybe 30 seconds) and the spark got enough outta whack that it caused some detonation leading to the KS code. So I really think I'm looking at a CPS issue of some sort here.

thanks!

[SappySE107]

I dont know how the CPS would get out of alignment. Its probably bad and needs to be replaced. The MAP code is usually just a byproduct of something else messing up.

[jmgtp]

I dont know how the CPS would get out of alignment. Its probably bad and needs to be replaced. The MAP code is usually just a byproduct of something else messing up.

I talked with my dad about this (electrical engineer) and he informed me that I should have tested the crank sensor using AC votlage not DC. So we went out to the car and sure enough it has AC voltage on the CPS harness (at the ICM end) while cranking. We then looked at the schematics in the GM manuals. The other 2 wire harness going into the ICM provides power to it, and I did earlier today measure 12v at this harness. So that leaves the 6 wire connector. The trouble shooting for the EST circuit goes through steps on how to test the 6 wire harness and determine if the problem exists with the ICM, ECM, or if faulty wiring may exist. I will be doing this tommorow. (for anyone whos interested its in Book 1, pg 6E3-A-53 of the GM manuals for 1991 Grand Prix).

Ironic note: we have 3 GM cars: my GP, my Beretta, and a Saturn. All 3 are currently broken. haha. Our Ford and Chrysler, as much as it hurts to say, have been pretty bullet proof, and our 2 Nissans have never once had a problem. >>>Just pissed at GM electronics right now, someone at AC Delco needs to burn in hell for this!

[jmgtp]

as I continually reply to my own thread... :P

I've been talking with Nico about this problem, and he brought it to my attention that as long as the ICM has power and signal from the CPS it will provide spark at speeds <400 rpm. I have power (measured it with a meter) and apparently have some signal from the CPS but no spark when cranking. Crapped out ICM? But 2 of them?! Both of which worked 2 weeks ago?

[jmgtp]

I checked the continuity of all the wires in the 6 wire harness on the ICM. All checked good with the exception of wire B (according to the schematic) which showed no continuity at ECM Harness C pin 9 (once again according to the schematic). With condition occured with ignition on/off. Can anyone verify that I should have continuity between pin B of 6 wire ICM harness anc pin C9 of ECM harness? In the schematic this wire is labeled EST. However, in the paragraph beneath the schematic it says that "an open or ground in the EST or bypass circuits will set a Code 42 and cause the engine to run on the ignition module timing." Well, I have no spark so I guess this is pointing back towards a bad module, but I still find it hard to believe that both of my spare modules can be bad when they both worked fine just 2 weeks ago and have seen no use since

[Homer]

Yes, if code 42 is set then the icm will be running all of the timming operations, that all goes back to below 400rpm the icm is running the timing and above 400rpm the ecm should be controling the timing. You should still get spark though, it wont be as accurate as if the ecm is giving the signal since the icm can only see the crank sensor and no other sensors. So technically all you need for the icm to send a spark signal to a coil is battery positive/negative and a crank sensor. Also you said you got a/c voltage from the cps but how do you know that it has the right wave height/length for the icm to reconginze it?

[jmgtp]

Also you said you got a/c voltage from the cps but how do you know that it has the right wave height/length for the icm to reconginze it?

I dont know, and it fluctuates somewhat when I taking a reading. This morning I got it to run. It just started up. It would rev in neutral, and rev if I held the clutch in so long as I was in neutral (ie thrust bearing should be ok). But when I tried to move the car it stalled and wouldnt start again. I swapped ICMs and Coil Packs with another set and I can get it to sputter when I crank (fires a bit) but it wont catch completely. Going to replace the CPS and hope that fixes the problem.

[jmgtp]

and my string of replies to my own post continues.

I think Ive narrowed it down to either the CPS or the CPS wiring.

Reasoning: I recalled the other night when it failed me for the second time (after restarting) I was in gear moving a good 20 mph. The tachometer was functioning up until the point the engine quit. But I was still in gear with the clutch engaged, the engine was still spinning. BUT the tach went to 0 even though the ignition was still on, it should have displayed engine rpm. The only possibility is that it was recieving no tach signal. So I can only assume the ICM and ECM also lost the tach signal. Just a few minutes ago I attempted to push the car into the garage but couldnt manage it alone (theres an incline plus I had to have the wheel cut, last time it had to be pushed in it took 3 of us) so I said what the hell I'll try to start it, if that doesnt work Ill step on the clutch switch and leave it in 1st and let the starter drag it in (ya i know killer on the starter). So I'm cranking away, go an enormously loud backfire I gotta take a look and see if my cone filter survived it but then some more cranking and it caught! If I gave it gas it would rev but above 2-3k it would start to randomly cut out, so I gently got it in the garage under idle power and let it sit to see how long it would idle. It didnt last 30 seconds before it quit, but thank God clutch disengagement had no effect on it (so thrust bearing should be ok). <--sorry that was one long boring unneccesary run on sentence!

I bought a new CPS today and will be changing it *maybe* tonite but I'm kinda tired so maybe not. That is all.

[jmgtp]

Changed CPS, it started. Ran 30 seconds and quit. So I checked it out some and it has spark now. Plopped a fuel pressure gauge on, and whatdya know NO fuel pressure at all, at least according to this gauge. And I believe it. If I turn the key to cycle the pump it should build some pressure. The gauge reads 0, and when I press the release on the gauge to vent the fuel about 2 drops piddle out. The fuel pump cycles though. Shitty that so much went wrong at the same time. Gonna change the fuel filter first to be sure it wasnt seriously clogged but I doubt that. O ya... just filled up 2 days ago so unless my tank has a gaping hole it should still be at least 3/4 full. So anyone have any luck with non delco replacement fuel pumps? Opinions on different brands?

i think i may be the only one whose looked at this thread.

[brian89gp]

I used a Walbro 255lph one, cost me $115 i think. Not sure how that compares to others though.

[Homer]

Its nice to see that you have spark...To check a cps you really need a multi-meter that can give a graph of volts, wave length, and wave height.

[pocket-rocket]

I think Ben has a 255lph Holley in his GP. Might not be a Holley though. I know it's 255lph though.

[jmgtp]

Its nice to see that you have spark...To check a cps you really need a multi-meter that can give a graph of volts, wave length, and wave height.

It has no spark again

Its intermittent. It'll run for 5 minutes then just quit, and when I check for spark there is none. A few minutes later it'll have spark again, then out again. It always has +12V and Ground to the ignition module, and there is always signal from the CPS (which is brand new) at the ICM end of the harness. As far as I know those are the only 2 requisites neccessary for spark. So either I have a bad ICM or 3 bad coil packs. There are no trouble codes. Ive tried spare ICMs and coils but they always lead to the same condition. Gotta find another set of ICM/coils I guess. This is getting so very tiring.

[pocket-rocket]

Have you checked your wires? I don't remember what kind of wires you have on that whore. I would think with bad wires the car would still run though. Didn't you move your coils/ICM? Might want to check your ground on it again.