Need Trouble code 42 help

[blacknight80]

I have a shop manual and I am not quite sure of one of the steps in the trouble shooting chart. It says to ground "test" terminal. What the heck do they mean? I am not sure if that means one specific wire in the four wire connector or se where else on the distributor. ATTACH=full]219197[/ATTACH]

Thanks

 

[RmvBfrFlght]

Odds are it is pin B is the ALDL connector. In '82 GM listed pin B as the "Diagnostic Test Terminal." I know that for the '86 & '87 ECMs, grounding that terminal sets the spark advance to a set 15* BTDC. Likely does something similar to the earlier models.

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[Freddie's Buick]

There's a green wire, (may have faded to a yellow from age), with a connector on it that is just hanging and not attached to anything. It is the ground wire for diagnostics on the older ECM's. You can sometimes find it buried near the alternator on the intake coming off of the wiring harness.

 

[blacknight80]

Ok I know where it is. So the ground test is just grounding that green connector?

 

[blacknight80]

 

[Freddie's Buick]

Ok I know where it is. So the ground test is just grounding that green connector?

Oops! Correction: (I forgot that lead is for checking the idle mixture with a dwell meter). It's at the ALDL as noted by RmvBfrFlght, but it's not the "B" terminal. Look at the pic.

 

[RmvBfrFlght]

Thanks for posting that. Having very little info on those years I learn something new everyday.

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[jimski]

I am chasing that same code 42, cannot figure it out. The timing will not retard under boost becouse of it.

 

[blacknight80]

I went through the diagnostic chart and when I remove the jumper from wire A to B with power to wire C in the dizzy EST connector the car turns off. So it sent me further down the chart it told me to check for a broke wire and my ohm meter read 0 or close to it on both wires to the ECM. That sends me to the next bullet that states if not grounded or open it is a faulty ECM connection or faulty ECM. What would my multi meter read if it was grounded? Should I just use my test light and hook up my negative to the positive terminal on my battery and probe the EST connector A and C wires and see if it lights up?
I gave my ECM a visual once over and I didn't see any cracks or burns so I am hoping it is ok. And the connection looks good and clean. This is not a t-top car but does have a astro roof, but I don't see any signs of water. From what I read this Is a sucker to solver.

 

[Freddie's Buick]

.... Should I just use my test light and hook up my negative to the positive terminal on my battery and probe the EST connector A and C wires and see if it lights up?

If my memory serves me correctly, I believe it's 5 volts. Word of advice, do not use a test light on anything that tracks back to the ECM. Check the wiring after you remove the ECM from the harness. It was built for minumal voltage. 12V in the wrong place and you will fry the ECM

 

[Freddie's Buick]

.... Should I just use my test light and hook up my negative to the positive terminal on my battery and probe the EST connector A and C wires and see if it lights up?

If my memory serves me correctly, I believe it's 5 volts. Word of advice, do not use a test light on anything that tracks back to the ECM. Check the wiring after you remove the ECM from the harness. It was built for minumal voltage. 12V in the wrong place and you will fry the ECM

 

[blacknight80]

The connection on the knock sensor is kinda iffy. Would this affect the est circuit? I'm going to clean up some grounds and hope this solves it.

 

[blacknight80]

I will stick to my multi meter for testing. So there should be 5 volts at the terminal with the ECM connected and car running?

 

[blacknight80]

I tested both sides of the est connector with the car running this is what I found

Dizzy side- A-0.2 volts
B-2.3 volts
C-0.2 volts
D-0 volts

Car side- A-0.1 volts
B-0.3 volts
C-4.5 volts
D-0.5 volts

Are any of these that are ready high or low?

When I disconnect the est connector slowly it stalls the car.

When the est is connected the mixture solenoid in the car chatters but stops if you unhook it.

Any help is appreciated. Thanks

 

[jimski]

I tested both sides of the est connector with the car running this is what I found

Dizzy side- A-0.2 volts
B-2.3 volts
C-0.2 volts
D-0 volts

Car side- A-0.1 volts
B-0.3 volts
C-4.5 volts
D-0.5 volts

Are any of these that are ready high or low?

When I disconnect the est connector slowly it stalls the car.

When the est is connected the mixture solenoid in the car chatters but stops if you unhook it.

Any help is appreciated. Thanks

If possible can you send me a good shot of that shop manual page for code 42. I would like to see if i can figure this out.

 

[blacknight80]

 

[blacknight80]

I checked the est wires right from the ECM connector in the cab to the connectors at the hei module and they are all showing 0 resistance. When I hook the hei module connector to the hei module I get resistance on wires A and C between the hei module and the dizzy side of the est connector. Does this indicate a blown hei module?

I cleaned every ground I could find and ab illusory it didn't sort anything out and all the wires from the ECM to the dizzy show no resistance so I think I can remove an open wire in the system. Where does the ECM ground to? Does it have a designated ground wire back to the chassis or is the ground strap at the rear of the block supposed to do it?

I'm running out of ideas on what to test and I really don't feel like replacing the entire ignition system or the ECM chasing this gremlin. I've read to many stories on all different gm vehicles with this problem and guys replace everything and it doesn't fix a thing.

Sorry for the continuous posting, I'm hoping if I keep throwing my updates out there I might trigger a thought from one of the b4b wizards out there.

Thanks

 

[jimski]

I checked the est wires right from the ECM connector in the cab to the connectors at the hei module and they are all showing 0 resistance. When I hook the hei module connector to the hei module I get resistance on wires A and C between the hei module and the dizzy side of the est connector. Does this indicate a blown hei module?

I cleaned every ground I could find and ab illusory it didn't sort anything out and all the wires from the ECM to the dizzy show no resistance so I think I can remove an open wire in the system. Where does the ECM ground to? Does it have a designated ground wire back to the chassis or is the ground strap at the rear of the block supposed to do it?

I'm running out of ideas on what to test and I really don't feel like replacing the entire ignition system or the ECM chasing this gremlin. I've read to many stories on all different gm vehicles with this problem and guys replace everything and it doesn't fix a thing.

Sorry for the continuous posting, I'm hoping if I keep throwing my updates out there I might trigger a thought from one of the b4b wizards out there.

Thanks

I replaced the hei and still code 42, i am about to change the whole dizzy with a second i have just to see.

 

[blacknight80]

I fiddled with the est system for a while. Pulled the ECM and did another visual inspection and found the paper that lines the inside of the ECM box lifted and touching the ECM. So I glued it down and I still have a check engine light on but only flashes a 12 code. I followed the flow chart for this issue but I can't seem to get to the bottom of it. I don't know what else I messed with but I mucked something up.

I also ran a direct wire from my battery to the dizzy. Not sure if this did it. The hei needs constant 12 volts to operate so it should have been ok.

 

[RmvBfrFlght]

The code 12 is likely normal. I know that the later ECMs (for EFI) flash code 12 when all is OK. All it means is that the engine isn't running, but the ECM is and isn't getting distributor reference pulses (DRPs). Which it won't as the distributor isn't moving.

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