I need help with my vette. I have replaced the opti spark, Ignition module, even the PMU. It still turns over and will not start. Any advice.

getting spark or fuel?

time to go back to the basics...

PMU? I am assume you mean the engine controller, right?

H42 should mean that the knock sensor has grounded. However, a bad knock sensor won't effect startup... it will still run, just not right.

I am getting spark and fuel. I don't know what else it could be?

I mean I bought a new computer the ecm

rarely will the ECM cause the car to not start or run... it will run badly, but still run most of the time.

If you ahve fuel, and spark, it should run.

I donno what to think... I donno if the opti can go on wrong or not, on the later versions, it can't, but I think it might on the earlier ones... it's been a LONG time since I replaced mine!!

did you check the knock sensor?

On my '93, I just cured code 42. It was either the ECM, the ignition control module, or the wiring in between. Sounds like you might have a wiring problem between the ECM and ICM.

Fix the code first. If you are getting fuel, spark, and air...at the right time, the engine should start.

Hang on a minute here, someone has jumped the gun. This is a 94, not a 92-93.

Code 42 isnt grounded Knock sensor, its this: [color=red]DTC #42: Ignition Control Circuit Shorted.[/color:5411916891] and you can bet your bollocks to a barn dance that WILL stop the engine starting if there is an issue there.

First thing is we need to really know what module number this DTC is from, cause DTC 42 could mean at least 2 things, If indeed its module 4, then yes, by all means, proceed along the said route, however its important to have the full facts before anyone starts to assume an issue is related to a DTC.

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But is it being delivered at the right time?

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Now we are getting somewhere. I have no refrence to a 94 DTC's, but if this is the correct code, it needs to be looked into. I imagine there is no spark with this code. A FSM would show the troubleshooting steps to take to find and fix the problem. Who's got it? If nothing else, someone just take a pic of the page in the FSM and post it. I would still try and troubleshoot the code first.

The Opti spark can most definetly be installed 180* out and you still get spark. Did you have to force it on? Get the #1 piston at TDC and it should have the arrow on the harmonic balancer at 12 o'clock position on compression stroke. If not, you will have to pull the opti and reinstall

Might want to also make sure the injectors are getting the ref pulses. This is done with a noid light. The light should blink with cranking or with the engine running.

Same as 95 DTCs. 92 and 93 are not the same.

All things aside, before anyone can coment with 100% accuracy we need to know what module the DTC was in, cause if this was a CCM DTC, its got little or nothing whatso ever to do with the car not starting.

The fact it has spark doesnt mean much in relation to the code, could be an intermitant fault that set the DTC, in which case it could still spark and may be erratic or not when it should be. Depends on what it is doing when this fault occurs and indeed depends on the fault at hand.

Now, the good book says this:

DTC 42 will set when: The PCM detects 84 crankshaft revolutions without IC activity.

[color=red]Action taken (PCM will default to):[/color:2b2b598c33] If DTC 42 is detected, the PCM will disable the fuel injectors to prevent flooding of the engine. DTC 42 will be stored in the PCM memory but will NOT turn on the malfunction indicator lamp.

Assuming your DTC 42 is indeed in module 4, that alone is a good enough indication as to why it wont start, and in this case, i cant see it being caused by the distributor being 180* out of whack.

I wont type any more from the service manual, i had to pay for it, and im sure you can all apreciate the fact i didnt buy it to save everyone else from buying one.

Wonder if the code was present before replacing the opti and ICM? It was stated that it is a history code. Yes, it would help to find out what module this code is in as well.

Might want to clear the codes and see if it comes back. I assume the battery was disconnected while the opti was installed and this should result in a current code.

That code will always come up with H as far as i know. Never bother reading too much into the H and C prefixes, 9 times out of 10 itll be H and that tells you very little about the issue really.

This code can only come up while the engine is not running (if it is running, the setting of this DTC will cause imediate shutoff)

Now you all do know this thread is 6 months old dont you?

It never even crossed my mind to look at the original date. Just noticed it and started blabbing away. Guess the car is most likely fixed by now. :silent:

HAHAHA!! No worries mate, still helps anyone that does a search later on, the thread was of very limited use as it sat before Lichen re-opened it, so we may as well give abit more info to work with for later searches