Hello, anyone ever had a code 42 and wind up doing something other than replace the ECM to correct it? My ECM is about two years old. I replaced the O2 sensor and PCV valve for the heck of it two weeks ago and the code did not pop in the next rain (it came up today again)... This code has popped up only in the rain, and 3 out of 4 times in the rain. Car seems fine in the dry and the manual says even with a code 42 the car should be drivable. I have to drive 2000 miles starting friday and need the car until then. This is a 1989 ZF6 car. Any help will be appreciated.

 

Hi Joe

I have an 89 with the same problem. I see that the code is intermittent like mine used to be. But now it comes on always.
Have you tried to drive the car full gas (wot)? If not try it, mine starts to miss between 4300 rpm and 4700rpm (until the trans shifts)
I have already changed the ignition module but nothing happened, last week i was at my mechanic and we scanned the engine with a scanner and it was advancing the timing as it should be doing because some body told me that if i have a failing esc module it could be the culprit but i am not sure that its it. I have a thread going right now maybe someone will give us a suggestion on what to do next.

 

ok, cool, thanks....can I track your updates on this thread so I can find it.....this problem is new for me, but i expect new problems or actually the car showing it's age as i go along. On thing i didn't mention is that when the check engine light comes on i notice about twice the power loss as when I switch on the A/C, basically feels like a loss of about 10-15% of power. That is across the board with different throttle inputs. Also if the A/C is on to keep the defogging action going, the car will just about stall at a stop, it drops to about 500-600 rpm. Next time I start the car it is fine. I love this car, it's ZF6 with Z51 and an FX3 delete, factory heavy duty radiator and oil cooler stock, I am told pretty unusual, a good base for a track car.
This forum is amazing, i started my threat 15 minutes ago! Man I am so glad I have gotten on here.

 

Intermittents are generally wiring problems and since your getting the code in the rain, suspect the bypass wire because the connector isn't far from the inner fender opening. It's tan and on a barrel plug near the brake booster. Make sure it's tight and you might want to smear a little dielectric on the contacts of the connector.

The a/c problem is best diagnosed with a scanner. Verify that the a/c signal reads "yes" when you turn on the defroster and that there is a corresponding increase in IAC counts (from about 12 to 20/25). A "yes" with no increase in counts is usually the ECM. No "yes" means there's no signal from the dash control. It comes in at ECM Pin B8 and will be 12 volts with manual air, about 5 or 7 volts with Electronic. If you have the "yes" and an increase in counts, suspect a dirty throttle body or an a/c compressor that is on it's last legs (sometimes you can smell the fan belt slipping as it tries to turn the compressor). A quick check would be to turn the compressor hub. Put a 10 mm socket on the bolt and it should turn with slight resistance, engine off.

 

Mine threw that same code; http://forums.corvetteforum.com/showthread.php?t=962048

Second reply is pretty informative, and another mechanic I talked to in "real life" said it's probably the pick up in the dist. as well.

 

Thanks for the reply on the A/C, I actually don't have an A/C problem, I was trying to say that to drop in engine power from that 42 code (when it shows itself) feels like about twice the drag on the engine felt when I do turn on the A/C. I will check that plug. I DID have an A/C problem last year, $1200 fixed that

 

Sorry for not replying again but i have not been on the net for acouple of days, mine has a drop in voltage too when you turn the ac on that is the same fault mine has when the code is on!
So what the h_ll is with this code? Iv'e been trying to fix it for a year and a half and can't find the cause.
Lets hope someone already had it and fixed it will tell us what to try next.