Code 42 Help

[XLR8]

I was driving the car last week and a code 42 appeared and the car ran very poor. This happened about 1 1/2 weeks after the engine was cleaned with simple green.

I have read every code 42 thread and following is a list of items that were done but I still get code 42 right after start-up.

1. Cleaned all contacts from module to harness - all looked good.
2. Cleaned contacts from ECM to harness - all looked good - all wiring looked good.
3. Removed chip and e-prom.
4. Tried a new chip.
5. Ran a new wire to replace the tan/black bypass wire from the ECM to the module.
6. Ran a new wire to replace the white EST wire from the ECM to the module.
7. Checked all grounds,
8. Checked negative and positive battery cables.
9. Someone said to check and see if cam sensor loose or broken - it was OK.
10. Replaced module.

Still code a 42 - any other ideas?

 

[Terry_H]

coil pack
ecm
ignition module

Can you borrow a known good replacement to check their operation?

 

[denn454]

if you give the guys at engines to go a call they would probably let you use their coil pack tester. shoots a spark between the towers, pretty cool thing. it would probably only cost you a 6 pack. there down on sannta fe and i want to say 6th, something like that. i don't know the area at all. and i had a spare coil pack that i let go with my car. if thats what it is let me know i can probably get one at a decent price. i think i paid $150 for mine maybe that was the module, i don't remember.

 

[XLR8]

Thanks Dennis. I'm going to call them tomorrow. I think their shop may be closed due to the GS Nats. I have a new GM Coil Pack and new GM module.

I'll try to find an ECM.

 

[salvageV6]

Assuming you get the code right back just after clearing it while idleing try this test.

IGN OFF. Disconnect both ECM connectors from the ECM.

Now turn the IGN ON, probe ECM harness connector terminal B4 with an ohmmeter to ground, B4 is the white EST wire, resistance should be less than 200 ohms was it?

Now use a test light and put the ground side to D5 terminal which is the bypass tan/blk wire. Put the hot side or other side of the lamp to a +12 source. IGN ON test is the lamp off? Connectors should still be off the ECM for this test also.

Now as the test lamp is put on this circuit the resistance from B4 white EST wire to ground should go from under 200 ohms to over 8000 ohms did it?

If the tests pass most likely it's in the ECM.

After reading and typing all this it's much simpler to test a spare ECM.

 

[XLR8]

By test light, can I just use a 12v bulb with 2 wires soldered to it?

 

[salvageV6]

Good question, I don't own one either, got tons of meters and some 89 trunk light bulbs with wires on them.

I'd use something low draw like the 89 or perhaps a dash type lamp bulb for the test.

194 I believe is the number for those, lower current than the 89 trunk light too.

Doesn't say in the "book" what the standard test lamp consists of.

 

[XLR8]

If it is the ECM, are they available at local type parts stores, or do I need to go through a Buick vendor?

 

[XLR8]

Originally posted by salvageV6
Assuming you get the code right back just after clearing it while idleing try this test.

IGN OFF. Disconnect both ECM connectors from the ECM.

Now turn the IGN ON, probe ECM harness connector terminal B4 with an ohmmeter to ground, B4 is the white EST wire, resistance should be less than 200 ohms was it?

Now use a test light and put the ground side to D5 terminal which is the bypass tan/blk wire. Put the hot side or other side of the lamp to a +12 source. IGN ON test is the lamp off? Connectors should still be off the ECM for this test also.

Now as the test lamp is put on this circuit the resistance from B4 white EST wire to ground should go from under 200 ohms to over 8000 ohms did it?

If the tests pass most likely it's in the ECM.

After reading and typing all this it's much simpler to test a spare ECM.

About time the site came back up!
I ran the tests.
12v light to D5 - IGN on - the test light was out (it was on when IGN was off).
The resistance from B4 to ground DID NOT CHANGE as the test light was applied - stayed under 200 Ohms.
Neither B4 nor B5 are open or shorted to ground ( ran new wires for both from the ECM to the Module plug just to be sure)
Any more ideas?
It still appears to be the module - I think I need to find someone in Denver that's not at the Nats. to see if their known good module will solve my problems - either that or take it into a shop.

 

[Whooshmobile]

I sent you an email.

 

[salvageV6]

According to the manual it should be the module.

I have never done that test to see the change does occur in ohms. Just relaying it to you.

Easier to change the spare module from Red Regal T out than do the test.

Definately get a good spare and try it.

 

[denn454]

you can do the module yourself. its really not that tough, just keep your fingers out of the goo. take the wire harness off theres a screw holding it in, pulling on it doesn't work, trust me. then if i remember right there are 1 or 2 bolts on the back side to take out. with that i think the whole module and coil pack slide right out. put your new coil pack on the module exactly like the old one is. (take it appart, 6 screws, be carefull of the goo!!!) reverse the process and your done.
dont' forget to watch your plug wires, mixing them up really makes you feel bad....

so you have a new module on the car thats acting up, or you have a spare one setting around? i do have a freiend with a t-type we could borrow his module for a few minutes i'm sure.

good luck!

 

[XLR8]

I bought a new module thinking that that was the problem. Put it on and same problem and the tests SalvageV6 gave me indicates it is still the module.

I have family in town this weekend so I may stop by Engines to Go on Tuesday to see if they have a known good module to try.

I wanna go racing!

 

[streetknight]

Just wondering if you ever found your code 42 problem. I was fighting the same thing.

 

[XLR8]

Yes, the problem was corrected. It turned out that one of the posts on the coil pack was cracked. There was arcing between the coil pack and module and the module fried. A new coil pack and module solved the problem.
The flow chart was a very helpful tool. After all the tests I ran I think I can disconnect and reconnect the car's ECM in 2 minutes.

Run the diagnostics on the flow chart and see where it leads. I'll be gald to answer any questions that I can although Salvage V6 knows a lot more than I do. Good luck finding the problem.

 

[Ron Coleman]

XLR8 thanks for comming back and giving us the update on the code 42, it will help out fellow buick members down the road.

thanks again!