Code 42

[Nicksturbo]

Battery went dead, got new battey started the car, and was getting code 42. the car was acting funny, eng check light went on, car stalled. disconnected emc, put it back check eng was off. Took the car out, came to a light car stalled. This was about two min. from my house. Can someone tell me what this code is and were on the car to look for it?
Thanks, Nick

 

[TurboTA3.8]

CODE 42

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.

An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing.

The conditions for setting this code are:

System in BYPASS mode but the ignition module is still controlling timing

- or -
Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.



Typical causes for this code include:

1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM

there ya go

george

 

[Nicksturbo]

Where do I find tis EST line. I am new to this car, Looks like I need to be a enginer.
Thanks, Nick

 

[Razor]

My vote is ignition module..then ecm..then wiring...

You can get a used one from RedRegalT in the for sale section for like 50 bucks...A good spare part to have on hand.Like an ecm,a MAF to add to those must have spares.

 

[Kyle F]

When I got my code 42, I wnet to autozone to get thier diagnosis sheet. Its a nice thing to have, all you need is an ohm meter and a test ligth for this. I started plugging away at their procedure and rulled out everything. Whch meant ECM, and after I figured it out with their sheet, my car started giving me a code that the water injection went bad. LOL I knew right then the ECM was trashed, got a new one from Advanced Auto Parts, overnight from a Saturday afternoon order picked it up Sunday morning... cant beat that, fo less than a $100, infact it was cheaper than the Ignition control Module.
Aanyways make sure you get the proper ECM, there are two listed for the 87 GN so beacareful.... you want the one that is listed for the GNX... This is if they dont list the TTA for you.

 

[Nicksturbo]

Looks like the bad battery set the code.Put the new battery in, cleared ecm, let run for 20 min, took it out so far so good.
Thanks again for the help.
Nick

 

[Kyle F]

I didnt know the batery could do that, but hey easy fix.
Glad you got it running right now!

 

[Nicksturbo]

Took it out again, code 42. Looks like ecm for me. Is it a big deal to cahnge. Any tips for easy install, Like disconnect battery, anything else. I look at wells ECM,a life time gaurantee
Thanks, Nick

 

[Kyle F]

Its not hard, just a pan in the back.
YOu have to lay in the passengers seat and floorbaord. Other than that its just up under neath the dash. Pretty easy just unplug one and plug the other in. Though when you get the computer it will not have a PROM or CAL Pak, so make sure you take yours out of your old one before you turn it on for a core.
ALso, alway dosconnect the negative battery terminal before doing any electrical work, just incase!

 

[Nicksturbo]

Thanks for the help, Kyle
Nick

 

[Kyle F]

Anytime

 

[Razor]

May or may not help...If you have a local U-Pull-it auto parts aka junkyard,most 86-88 buicks and oldsmobiles have the same ECM.I picked up my last one for 35 bucks..just look for cars that use the same coil packs..and usually they'll have the same ecm..It has the 7148 part number prefix..Calpacks and chips will be different but easy to swap..squeeze the connectors and out they go..And theyre located in the area above the passenger floor torwards the firewall.Yank down the glove box and whalla.

And keep your ecm..if its original TTA it has special stickers that correllate with the stock eprom chip..AGX

But thats another story
HTH

 

[Nicksturbo]

Thanks for the info, Razor.
Nick

 

[Nicksturbo]

I change the ECM on the car, so far it looks like that was it.
Thanks to everybody, who tried to help.
Nick