So I read through the search, seems there is not one single main cause for the code 42. Some people have ECM related problems, others have ignition module problems, some claim, spark plug wires, coil wires and other related issues.

Well here is the story on this one.

Its a friends car.

86SE V6 Auto.

New in the last 3 months.
MSD Blaster II Coil, (Series 2 new design)
MSD Superconductor Wires, Red Build them yourself kit.
Neihoff Ignition Control Module

New in the last 12 months
Pick Up coil and rebuilt distributor shaft.


Car runs and drives, however has a hesitation. Will bog down randomly, however if you PIN the throttle to the floor, it will take off and run fine. It has not done any signs of normal module failure with heat or anything. It actually runs pretty good at idle and over 3/4 throttle.

When shut off and and restarted the Check Engine light does not come on for the first 10 or so mins. Car runs perfect until light comes on.


I am wondering, is it possible for the ECM to start to fail? I did a visual inspection on all the plugs and wires that I could see and can't find anything out of place. We even Zip Tied the 2 coil connectors down to the coil just to make sure they were not bumping around causing an intermittent issue.

As a precaution, I have sent Fiero Chick and him to another Fiero guys place to pick up a bunch of spare parts. Complete Dist Shaft, sensors and other engine wiring bits from a spare motor that was pulled to do a 3.8 SC Swap. Before we just start randomly buying parts for the car we are going to test some known good parts and see if the problem will go away.

Anyone got an other Code 42 input?

------------------
85GT,93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

Read this even though it's for the Syclone:

http://www.syty.org/old/d&e-code42.html

Code 42 is caused by an open or short in the bypass line.

If you have an ohm meter run the tests and check for continuity from the ECM to the module. The failure itself is pretty straightforward. If that line disconnects while driving it will do exactly what you said.

My first guess would be the pins at the ECM and second, the pins at the module. After that, you will have to look in the harness.

[This message has been edited by TK (edited 09-27-2008).]

It's also caused by crappy grounds. The module grounds thru the mounting screws.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top of every forum page...)

Well we think we found the problem. The 2 plugs that go into the coil, the prongs on the connectors were really corroded. Not sure if they got corroded from being loose and bouncing around or what, but I cleaned them up, and then re-zip tied them in place and he is taking it for a test run now. I will post back and let you guys know the details.

Good find! Let us know.

Well the cleaning of the connector did not fix it, so I removed the main ECM ground in the center console and cleaned it and sent him for a drive, still did not fix it.

UGH. So I pulled the new module out, and replaced it with a used GM one that I had sitting in a parts box and he is going on a test drive now. I will post back with the results when he gets back.

Oh, I thought you swapped that. Either way, a fix is a fix!

quote Originally posted by Capt Fiero: Well he just called me, the first thing I thought when I saw his name show up on call display was FU(*() The used module died and he is stranded. Nope. He took it on the side streets and all was well, he took it on the highway to the next town over, (about 15 min drive) everything is perfect. He just got back as I was typing this reply. It was the new module had an intermittent problem. So he is going to go ahead and buy yet another module and keep one in the car as a spare at all times.

I know I sound like a broken record but the V6 Fiero just seems to hate modules other than AC Delco. I went through 2 Fierostore E-Tron modules and another brand (I can't remember) in the last few years. Once I put in the AC Delco one, I haven't seen a 42 since April 2006.

The other big thing is what Ogre's been saying, make sure the 2 mounting screws are clean and have a good contact because those are your ground.

------------------
=-Eric the Dread

1988 Fiero GT 2.8L V6
2001 Grand Prix GTP SC3.8L V6

Yea, I have never heard of a Neihoff anything. I would stick to major brands.

Does anyone have any bad Ignition modules they would be willing to let me have? Im looking to get one of each major brand, I have a wells so far.

I dont actually even need the ICM itself, if you dont want to ship it, just pop the cover off the middle and take a picture of the chip and darlington in there, I would like to see what diffrences there are between brands and what an original GM looks like, to see if there is any merit to the claims that GM ones are better. I think they might be, but Id like to know for sure.