Bought the car 2 months ago. Probably put 2000 miles on it. Ran like a champ, no problems. Replaced weather stripping and put new wheels on it......now to get to the point: 4 days ago tried to crank it up and it was hard to start, idled at 3000 rpm for a few seconds, coughed and then died right there in my driveway. Hasn't been able to start since that time. I used the paperclip method and got these codes:

1 H31 H33 H35 H37

4 H36 H42

I'm stumped.

anybody with some C4 insight, please send suggestions. I am not very mechanically inclined, but from the reading that I have done, it could be 20 something different things........ very frustrated

bartftodd@gmail.com

 

Well your mechanically inclined enough to get the codes and make an attempt on it.

Module 4 is the powertrain control module (PCM) and the one you are interested in.
Code 36 is the high resolution pulse from the opti (distributor) which is used for fine tuning the timing but will not kill the engine. Code 42 is “ignition control circuit shorted” which relates to the coil, ICM and power to it. The code points to an area of the ignition system and not necessarily to a particular part.

Can't exactly say what is wrong from this code and the code could have been stored in the computer (PCM) for some time. It would not be right to just run with this code and jump into something without being sure it is really valid. The codes should be cleared and see if they re-occur. You can disconnect the battery for a minute and that would clear the codes (as well as the memory on the radio).

You can check fuse #25 10 amp to make sure it is good (coil, ignition 12 volts).

Check for spark off the coil and the plug wires.

Don’t know if you are capable but a fuel pressure check would be in order also. Can you hear your fuel pump run (rear of the car) for 2 seconds when you turn your key to just the “on” position.

 

Those stored codes could be "old".

Might want to disconnect the battery to reset them and try to start it again.

Check for "spark" at the wires with clamp on timing light.


Was the car stored outside just before death?


Ensure that the exaust pipes are unobstruckted... I've seen exaust tail pipes jammed up with "stuff" that local trouble making riff-raff loaded up to choke out an owners' engine.

 

Was on my iphone at work earlier, working from memory. I have added 1 code that was found Module 1 H35

I have the 2 book set GM Service Manuals for this car. I AM NOT a mechanic, but I did clear the codes by disconnecting the battery, got a C12, then turned ignition to on without trying to start, and got the above mentioned codes. This car ran like a top for 2 months, and I drove it 5 days a week (20 miles round trip). From the reading that I've been doing, I'm beginning to think it is that "optispark" I hope not. I am going to check and see if I can hear fuel pump when I turn key now.

Thanks for all advice and I appreciate any suggestions/tips.

 

Turned the key and listened for fuel pump. Pretty sure I heard a low whinning sound for about 2 seconds then nothing. Hopefully that was the fuel pump.........

 

If you cleared the codes by disconnecting the neg. bat. terminal and then immediatley re-read the same error codes without turning over the engine, then you did not successfully clear the previous History codes.
You typically need to leave the neg. bat. terminal disconnected for at least 30 seconds on more. I have had this problem before where the codes didn't clear the first time I tried.

Here is a full proof method of clearing your error codes without disconnecting the neg. bat. terminal :

To clear the codes,

1. With ignition "off" ground terminal #12 of the DLC (use bent paper clip to connect pin 4 to pin 12)

2. Turn ignition "on".

3. Press trip/odo button on the DIC until 1.7 appears in the trip
monitor area of the instrument cluster.

4. Press eng/met button on the DIC & hold until "---" appears in the
speedometer area of the cluster, this will clear CCM DTC'S.


To clear PCM/ECM codes do the following:

1. Press the trip reset button on the DIC until the desired system is displayed. In this case it will be 4.0.

2. Press trip/odo button on the DIC until the desired diagnostic mode(4.7) is displayed on the trip monitor area of the cluster.

3. Press & hold the eng/met button on the DIC until "---" is
displayed in the speedometer area of the cluster, this will clear PCM codes.

Once you have verified that you have cleared all history error codes, then try to restart engine several times and check again for codes and repost here.

 

AL B is probably right in the text book way to clear the codes. (I was trying to spare you to many works and keep things simple). If you connected the battery cable to soon it might not have cleared the codes.

If you do hear the fuel pump working for the 2 seconds chances are there is probably fuel pressure at least enough for the engine at least fire or start. So forgetting about intermittent fuel pumps or clogged fuel filters chances are the fuel pressure is OK.

Based on the current information I would make a guess there is no spark to the plugs. I could not even venture an accurate answer as to why. But you do at least do need to check for spark off the plugs and coil wire to verify.

Most opti's just don’t quit dead but rather cause some kind of poor running of the engine. The ICM (ignition control module) is more prone to dying over night. But without more to go on these are just possibilities and making some assumptions.

Then also there is the possibility of a poor connection at a connector or plug.

 

I think someone else asked the question, but did the front of your engine(ie where the opti resides) get wet ?? If your opti got a bath somehow, that can stop an opti in its tracks. Check to make sure that your water pump is not leaking from the weep hole. The weep hole is located directly above the Opti.....go figure !!!

How many miles on your '94, and do you have any maintanence history from the previous owner ?

 

154,000 miles (i know) no maintenance records. I got a really good deal on the car though

No, no abnormal moisture could have gotten to it. Parked under carport all night, next morning.......it rumbled for a few seconds, then died.

going outside now to be sure that I reset codes correctly and get another reading.
Definitely can hear the fuel pump for 2 seconds upon turning key to on position.

 

Ok, first I would like to thank you guys for your patience with my apparent ignorance!

That said, I followed the instructions for clearing the codes, tried starting 5 or 6 times after that, now when I check codes (checked about 4 times) all I get is C12 and no codes for any modules thereafter just ---

could it be as simple as me replacing fuel filter? well I bought one $12, so that's my next move.......can't hurt.

 

anybody got a link for a step by step guide on changing fuel filter for dummies

 

I know you want to make a valid attempt to do something by helping yourself and fixing the car. But let me just say that on most cars a fuel filer replacement is a routine job. But the location of the fuel filter in the vette makes is a rather difficult job even with a good compliment of a variety of good tools.

It is up under the right front inner wheel well area. Jacking it up is a must and getting the wrenches on it and turning the nuts can be a difficult effort. There are a few methods that are used to do this. The starter can be removed or the fuel pipe can be disconnected if you can get the lower nut loose on the filter and take the whole thing out. Any approach is just not simple.

But when fuel filters clogges up, they do it gradually and generally restrict flow affecting acceleration or high end cruise where lots of fuel is required. But even a partially restricted filter will pressurize the fuel system enabling the engine to start and run.

I just don’t think the fuel filter is going to turn out to be the problem. Before you jump into this, I really think you should check for spark at the coil and plugs. At least then you will have some real data and a positive direction. Checking for spark is easier to do than replacing the fuel filter.

 

Thank you for the direction. Just woke up, gonna drink a cup of coffee, get set up to check for spark, then call the wife out to be my 'ignition turner'.

What is puzzling me is the fact that now that I've cleared the codes correctly........I am getting no codes at all. Gonna check that again today as well.

Also, not sure if this would have any bearing on the no start, but I found a wire that stems off of another set of wires that plug into the bottom of the ASR that is unplugged, but I can't seem to locate anything that it could connect to. It is definitely not a ground, it has a quick connect fitting with a spring in it.

 

The on board diagnostics and computer system only monitor relatively a few points in the car as compared as to everything that can be monitored. GM selected what they thought was the most important or critical points in their opinion. Some of the codes are more relevant than others. The codes point to an area and not necessary a part (unlike HAL the computer).

By not having a code now just indicates the things it is looking at looks OK to the PCM but that does not mean all is good and that there is not a problem somewhere else. If there is no spark than chances are the problem is in the ignition system or at least you start there.

The wire hanging I believe goes over to the side of the master cylinder. On the passenger side of the master in the middle toward the bottom there should be a connector that is round. I believe your loose wire would go there especially if there is not a connection on it now. It's part of the brake failure warning system.

 

I agree with pcolt94's diagnostics here. The fuel filter is pretty much a PITA to replace, and they typically don't clog 100% to where you would have a no start condition. You need to familiarize yourself with the ignition system to better understand the problem. Follow pcolt94's advice and hold off on the fuel filter change, and check for spark first.

 

Ok guys! I got brave and got the wife involved. Pulled a plug wire and I'm getting NO SPARK

Still no diagnostics codes whatsoever since I cleared them as instructed? Still stumped.

Thanks for your leadership. Please keep directing me

 

That 10 amp fuse in the diagram should be checked. The diagram is for a 95 but my 94 fuse lay out shows fuse #25 and not fuse #11. (As I originally stated). The fuse panel is on the passenger side, in side of a small plastic door, above and to the right of your knee. The fuse door faces the passenger door and you need to open the passenger door to see it. A little 1/2 turn snap opens it.

Do you have a DVM and know how to measure voltage? Need to know this because some measurements need to be made. I don’t believe you are going to be able to find the problem or fix it using codes, so some real troubleshooting would need to be performed.

 

Just got codes 1 - 1 H31 H33 H35 H37

 

Those codes looks like they are from module 1 which is the chassis computer. I don’t have those codes with me here but they probably have nothing to do with the engine running or your problem. There are 3 computers in the car each with its own set of specific codes. Module 1 is the CCM, Module 4 is the PCM (the one you are interested in), and module 9 is the brake computer.

Can't tell anything more at this point. I will check those codes later anyway.

 

I think you need to let us know if you have a decent set of tools and a DVM. Also, how much wrenching experience do you have.....

Anyway, the following stuff is pretty simple to do......

So you verified you are not getting spark from a plug. OK good.
Next thing I would do is trace problem back from Opti:
1) verify that the 10amp fuse that feeds your coil is not fried.
2) trace back from Opti.....check to see if coil has spark. (use old spark plug wire and plug directly into the coil and see if spark jumps spark to part of the engine as wife cranks engine. Don't try to pull the coil wire off of the Opti on the driver side as it is next to impossable to get at.)
3) if no spark from coil, remove coil/ICM assembly from front of engine.(pretty easy to do)
4) have ICM tested at your local Advance, auto zone or O'riellys.
5) replace ICM if defective.