Just bought a GN Code 42 and other issues

[thegerm]

Hey guys. I just bought a 1986 Grand National. The car is completely stock except for a air cleaner and had a hypertech chip in it. I brought the car home on a trailer, it was idling high when I test drove it but seemed to drive ok. The previous owner had replaced the MAF, TPS, ICM, ECM, Coil pack, Cam sensor, 1 injector on number 3, plug wires, and spliced the injector harness.
I started doing the spring cleaning to the car, changed the fluids, plugs, cleaned the MAF, replaced the O2 sensor and was adjusting the IAC and TPS. I have a Scanmaster and a Scan tool for the car. The TPS was set at 1.2 and IAC was at 175. So I adjusted down the TPS to .46 and the check engine light came on sometime during all of this. Code was 42. I adjusted the IAC down to 46 counts and the TPS sensor down to .44 and the cars idles a lot better but pops if you rev the engine up. Reset the ECM and am still getting a code 42. So I replaced the Hypertech chip with a stock chip, wiped the codes and I am still getting a code 42. I found a few articles that had flow charts on testing for a code 42 all of my tests pointed to a bad ICM, so I replaced the ICM with a new one and am still getting a code 42. Plug wires are on the right posts on the coil pack. I hate to throw parts at this car but I'm kind of at a loss here. Was hoping someone could give me some insight on what to do next or what to test. I haven't drove the car since I brought it home 3 weeks ago....

 

[bpman1234]

How are your grounds?make sure you have a good connection to the coilmodule pack also the plug the goes to to module take it out and look at the pins .all straight?

 

[thegerm]

All the pins are straight, from what I've seen the grounds look good. I'll double check them and see or I'll run a new ground right to the plate the ICM mounts to.

 

[TURBOELKY]

I'll never forget my battle with code 42. You are on the right path with grounds. Check grounds on back of passenger head too. Check all the damn grounds while you're at it

 

[thegerm]

I'll never forget my battle with code 42. You are on the right path with grounds. Check grounds on back of passenger head too. Check all the damn grounds while you're at it

Lol I will.

 

[Heskahoka]

First, congrats on the car, it sounds like you are doing all the right things to it.
Here is a diagram of your whole CCCI system which may help:
http://www.installationinstructions.com/FYI/ccci-info.pdf

A few things to try:
1. Clean the contacts on your chip and the spring holder where the chip plugs in. Oxidation or loose spring pressure will throw a 42.
2. Check the plug that plugs into the ICM. Check for corroded pins, loose frayed wires.
3. Where did you buy your Ignition Control Module? There have been issues with aftermarket ICMs from AutoZone etc.

 

[thegerm]

I checked all the grounds tonight and added a few extra from the block to the ICM bracket and from the battery to the block. This didn't change anything. I checked the ICM harness it looks good, checked for bent pins or corroded pins and connections and they all look good.
I bought the ICM from napa. Was able to get a AC Delco brand. Not sure if that was a great choice or not but it sounded better than the other off brands.
Found a local place I can pick up a ECM for 60 bucks exchanged. They said if it doesn't work I could return it. So I might try them and see.

 

[TurboBuRick]

Is the maf stock or aluminum with tanslator?

 

[hgh518]

I'm fighting the exact same problem. Mine quit out of nowhere last nite. Spent all day chasing things down. My icm blew out along with my crankshaft sensor. Replaced those and started getting spark again. Ohmed out all icm wires to ecm all checked good. So that only leaves the ecm for me.

 

[thegerm]

Is the maf stock or aluminum with tanslator?

Stock Maf. No translator.

 

[thegerm]

I'm fighting the exact same problem. Mine quit out of nowhere last nite. Spent all day chasing things down. My icm blew out along with my crankshaft sensor. Replaced those and started getting spark again. Ohmed out all icm wires to ecm all checked good. So that only leaves the ecm for me.

Yea I've done the same thing.

 

[TurboBuRick]

Code 42 means the est signal is not getting back to the ecm. The est wire runs from the ignition module back to the ecm. Pin A on the module side to pin B4 on the ecm. Ohm the wire from the module plug to the ecm plug and see whats up.

 

[hgh518]

Code 42 means the est signal is not getting back to the ecm. The est wire runs from the ignition module back to the ecm. Pin A on the module side to pin B4 on the ecm. Ohm the wire from the module plug to the ecm plug and see whats up.[/QUO



I did that. That's how I know the ECM has to bad. I checked resistance on the est and the bypass wire.

 

[thegerm]

I just put a ECM in the car and it fixed it. Code is gone. Now on to figuring out how to make it run better.

 

[hgh518]

I just put a ECM in the car and it fixed it. Code is gone. Now on to figuring out how to make it run better.

My ecm will be here today at 3. Can't wait to try it and see.

 

[thegerm]

My ecm will be here today at 3. Can't wait to try it and see.

Did it fix your problem?