1982 CE throws a code 42 only when the ambient temperature is above 70 degrees and the engine is cold. After a warmup period of roughly 3 to 4 minutes and after shutting engine off for 30 seconds, the code goes away and engine runs fine. Has been doing this for quite some time. Any thoughts?

 

I had code 42 for the longest. Did every diagnosis I could and had some professionals give me advice. Went away when I replaced the ecm. Tedious, but not hard to do. Tedious because hard to get to. In battery box under driver seat. But once you figure out how to unscrew the holding screws, its a plug and play. An Al Cardone box via Autozone. Been using it for 4 years or more now with no problems.

 

Before you change the ECM, remove all the connections from the ECM including any grounding connections. Clean everything, then put so contact grease on to prevent future tarnishing. Dirty contacts and grounds will cause a lot of issues with an ECM.

 

I am not doubting you, but if I am going to do all that, I would just replace the ecm. You have done 90% of the work just getting to the connectors.

Your choice.

 

Once you get to the ECM and have removed cables/cleaned connections, what effort would it take to just plug it back in and try it?

THEN if you still get a code 42, you can EASILY replace the ECM, if needed. If not, button it up and drive....

 

Agreed

 

Thanks for the response, sorry for my delay in responding, I have been away. Regarding changing the ECM, if I start the car when outside temp is 65 degrees or below, I never get a code 42. It only seems to happen when the outside temp is above 70 degrees. Would that indicate a bad ECM?

 

You have suggestions on how to proceed. You may, however, go any direction you wish to go with your car.

 

Code 42 is your 'electronic spark timing' circuit...as we all know

For what this is worth,...because I have had many do just what yours is doing.

You are aware of the connection (tan wire with a black stripe) that you have to disconnect to set your timing???

Well that connector from GM is a bad design that did not last for long and when they start getting age on them. And with your car being a 1982...that is fairly old and what can happen is due to this connector is that black plastic design that does not keep dirt and moisture out of it...it can go bad.

What I have found is that I cut that connector out and install the type that GM used in later years that has the silicone seals in them and that stops the problem.

And...when the car gets hotter and the heat in the engine compartment increases...it effects that connector...and WHAM...you get that trouble code.

I am not stating that this will completely fix your problem...but if your car were in my shop and you are not the type that is worried about being 100% factory correct...I would cut that connector out and replace it like I wrote and see if that does it. And I have at times in order to show my customer that I feel I am on the right track.... that I will use a house wire nut to temporarily connect the two cut wires together and let them drive it for a few hours/days and when they comeback and the check engine light had not come back on...then they believe me and I install the weatherpac connectors.

And I ahve had to do that on many corvettes...just saying.

And I have also tried to save the facotry set-up for those customers who want it all original..and sometimes I am successful with that and sometimes the plastic and terminals just don to want to stay put and keep a good connection and that is when I run a jumper wire from one side of the connection to the other side and tape it up. That way...the factory connector is still intact and the circuit is good..and if the car is going to a show and being judged..the owner can take it a part for judging.

DUB

 

Thanks 7t1vette for the response however, as you can see, Dub has offered another possibility so I guess it doesn't hurt to keep asking. Also thanks Dub for the detailed response, I will check it out.

 

Yes...."another" possibility...of removing the connectors and evaluating them for good connection.

Hmmmmm.....sounds familiar, somehow. Perhaps, you should have already done so, and maybe you would not still have the problem.

{perhaps, you should re-read post #3}

 

...but to be totally honest....I would only concentrate on the wires and connectors that are a part of the circuit that the trouble code is referencing.

Pulling the connectors for TPS, MAP sensor, O2 sensor and so on that are not having a problem is something I know I would not do....especially if my scanner is showing them to be working and not have any trouble codes for any of them.

Because if the car is doing fine and there is only one code or a few..I would not even get into the computer area and any of the computer ground unless I had to and have exhausted all of my preliminary tests.

I choose to work smart and not hard especially when I am getting paid to fix it.

'Never2old'

One other thing to check and is not the cause for your trouble code...but does fall right in line with what '7T1vette' mentioned ...and that is the fuse ( 20 amp I believe) that is installed all by itself in your back right hand corner of your battery box. When the car is running... hold it and feel and see if it is getting hot. If it is..take out the fuse and clean it along with the terminals in the fuse block and check it again. That fuse is the fuse for your ECM and also the fuel pump relay if I am not mistaken and something else that I am forgetting but I think it is the oil pressure sender on the back of the engine block.

DUB

 

We just have a different strategy for the connectors, DUB. BECAUSE it is a 30+ year-old vehicle, I would ALWAYS choose to remove all of the connectors and evaluate them for integrity and for any indication of corrosion. You may have a code #42 this week; but all of those connections have risk of deterioration.

Better to stave off any other trouble codes by cleaning all of the contacts, cleaning/repairing any grounds, and protecting them from corrosion for the next 30 years. Then, you can put the ECM/connectors/grounds 'to bed'.

 

1000%....but I can not work for free...so that might partly be why the strategy is different.

I am not doing this on my car....I am doing it on other peoples cars. If the customer does not want to pay for it.....I am not going to spend hours doing anything that the owner of the car feels is a waste of money and won't pay for....even though I have advised them the importance. I know some may feel that is not right. And like it is my responsibility to make sure all cars are perfect when they leave even if it costs me my own money and time.

Well...if anyone feels that is how it should be done...then go and work for a week at your job and tell them you did it all for free...and oyu do not want any money..and see how long you do that.

From time to time...I get told by my customers..."Don't mess with what ain't broke".

And...it does happen...from time to time...they will come back a week or two later with another trouble code issue and I just look a them after I proved to them it is another trouble code and not the one I just repaired showing up.

I again ask them if they want me to do thorough check on it or only fix what is broke. And often times..but not always..all they want to only fix what is broke. Not realizing that there is a charge for me to run diagnostics to verify what I need to replace.

What more can I do???

DUB

 

DUB, I thought we were trying to advise another individual of how to resolve HIS problem. How did this turn into a discussion of your working for a living? Unless you are actually working on the OP's car on this issue, I don't understand why this is being discussed.

I'm offering advice and my reasoning to the OP for his consideration. I have no beef with you or with how you do this type work for a "paying customer".

 

Like I said before, its not rocket science and we are not solving the problems of the world. Replace the ecm for less than $200 and be done. Anything different you are just trying to prove something that can be solved in one fell swoop.

When I have my code 42 problems for years, I tried everything suggested. One day, when having my differential replaced, discussed with the manager. He researched on some site and found it was the ecm. Had it fixed within a week or two, mostly waiting for the new ecm to arrive.

 

I know it is a stretch... but I do have some people who appreciate a professionals point of view when it comes to repairs...it is a different perspective. Sorry that what I do rattles your cage....so...I will shut up...because I wrote what I needed to.

I know I can not please everyone here on the Corvette forum and never try to.

DUB

 

Personally, I value your information and your experience. I can take it or leave it. Witness my comments regarding just replacing the ecm. Keep up the good work.