Dying GN and code 42

[Timbuick]

Hi Guys, my car started acting up at low rpm this week. Today I drove less than a mile with the car starting to break down. It finally died on my driveway. I eventually got thee car restarted and it showed code 42.
Prior to this, the car did not show codes, but still ran poorly at low rpm and could break down without warning. At higher throttle on the open road it was fine.
I have;
changed MAF
coilpack
checked leads and plugs
checked cam sensor
02 sensor
All scantool numbers were god except the code 42 today

I note that when I turn ign on/not running, my FP guage (in car) shows 'Lo' for a moment before coming up to 43, then down to 37/8

I have no idea what is causing the problem.
I spent all of June chasing a high throtle backfire and 'cured' it.
Now I have the inverse problem and am runing out of ideas.

 

[XLR8]

My code 42 was a bad module.

 

[Timbuick]

What sort of symptoms did you get?

 

[TurboBuRick]

Copy/Paste

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

 

[Timbuick]

Thanks, I reset the ECM and the code did not return. That said, there is clearly a problem to work through it's just trying to work out exactly where it lies.

 

[Clark6]

I also had a code 42 last month.
I was unscrewing the bolt that hold the EST block to the side wall.
I got the screws but the EST block dropped from the wall down to the mid part of the engine.
I pulled out my extension mini magnet and kept trying to brush accross the top of it to catch that metal tab.
Well I picked it up plugged it back and screwed it in, switched on the engine and the code came.
I remembered that a lot of electronics especially circuit boards DO NOT LIKE MAGNETISM. You can actually magnetize and make some of the components inside to change position and mess up something. I kept unplugging and plugged it back up & it returned to normal.

So no magnets on things like that, just for future reference.

 

[XLR8]

What sort of symptoms did you get?

A code 42 and it was rough running. Try to borrower a known good module to put on your car - that's what I did.

 

[hiboom]

code 42

code 42 ended up being a wiring problem on my t type the only way it was tracked down was using alldata trouble shooting tree for no start, code 42 present. once I got it started it became a matter of wiggling wires from the ignition module and injector harness and listening for a idle change and replacing the 20 year old connectors.this was after changing every sensor and module on the car and not fixing it.All I'm saying it's a lot easier to follow procedure then just guessing putting on parts cheaper to. good luck

 

[billhead]

code 42

My code 42 was a bad module

 

[salvageV6]

Mine was wiring or a connector.

Had it randomly once or twice a year for 4 out of the first 7 years with the Translator +.

Haven't had one in the last two years.

I'd check and reseat the chip and ECM connectors.

Clean them with some plastic safe electronics spray if you can too.

 

[Timbuick]

Thanks guys, I checked the ECM wiring and appeared to be good and tight. I have reset the chip/ecm orange wire.The strange thing is that it starts and runs just fine, but starts to break down once warmed up and adding a little throttle.
Looks like a long job going thru the wiring:frown:

 

[TurboBuRick]

Do you have a scanmaster or a powerlogger?

When you first start the car, the ecm is in open loop. Running like a carborated car. Once warmed up it goes into closed loop and the ecm is correcting fuel based on the feedback from the o2.

It sounds to me like it could be a bad o2 or bad grounds on the back of the passenger head. If the o2 is reading wrong, you will have diveability issues. Other things that might mess with the o2 sensor would be vacuum leaks and/or pre o2 exhaust leaks.

HTH

 

[Timbuick]

I have a scanmaster showing all good readings except BLMs which rise to 139, but this was the case prior to the current problem. I swapped out the 02 sensor for a known good one, but no change. Your point about open/closed loop is interesting although i have a TT5.6 chip in the car.

 

[89mulletbird]

Tim - have you resolved this? I'm having the same issue and have replaced almost everything in the car to no avail....

Dave

 

[Timbuick]

Dave, I thought I had! It was fine for a couple of weeks but has returned. i'm sorting a brake problem currently, when thats done i'm probably going to a local rolling road to try and replicate the problem and see if it can be diagnosed.

From searching this site it appears a regular problem with many possible causes. If I get a result i'll make sure I post back. Best of luck!

 

[89mulletbird]

Hi Tim,

I'm still struggling with mine also.. I've changed

ECM
PROM
Ign module
Coil pack
Cam sensor cap
Crank sensor
Battery
Cleaned all engine grounds

On my latest test drive, I've noticed I might only get the backfiring while in 3rd gear... I was in OD and shifted to drive and the car started backfiring, shifted back to OD and it was fine... I've never had it happen in town, only on freeways when I'm in at least 3rd gear.

Going to change plug wires this week and see if that's it.

Dave

 

[Timbuick]

Hi Dave, whilst out yesterday I got the chance to use the car at WOT and had no misfire/backfire etc.The last thing I changed was the spark leads.
Despite the Mallory leads ohming out correctly, I put on an oder set of Delco leads and that seems to have helped. I hope it works for you.
I also suspect the MAF and will be upgrading to LS1/Translator in the new year.

 

[89mulletbird]

Spark leads = Spark plug wires?

 

[Timbuick]

Yes, spark plug wires.