Code 42 Help
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Joined: May 2001
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From: Royal Oak, MI
Code 42 Help
I'm hoping someone here can help me with this interesting problem.
First things first, this is an 85 with 90,000 miles and no engine mods to speak of, there are about 2,000 miles on a new cap/rotor/plugs/wires/etc. At the end of the season last year my heater core imploded, so I bypassed it with intentions of repairing over the winter. Of course life interferred with that plan and it didn't happen.
Last weekend I started the car for the first time in a couple of months and immediately the SES lights up, first time I had ever seen that light on my dash. I pull the code and it's a 42, so I look up here (http://home.fuse.net/c4/) and find out that is the code for the Electronic Spark Timing Circuit. Searching the forums has led me to a couple of preliminary things that I have checked, clearing the code each time (base timing wire connection, tight plug wires on the cap, "tapping" on the ECM).
My question is this, in the collective forum opinion, what the hell happened here? And what do I do from here?
First things first, this is an 85 with 90,000 miles and no engine mods to speak of, there are about 2,000 miles on a new cap/rotor/plugs/wires/etc. At the end of the season last year my heater core imploded, so I bypassed it with intentions of repairing over the winter. Of course life interferred with that plan and it didn't happen.
Last weekend I started the car for the first time in a couple of months and immediately the SES lights up, first time I had ever seen that light on my dash. I pull the code and it's a 42, so I look up here (http://home.fuse.net/c4/) and find out that is the code for the Electronic Spark Timing Circuit. Searching the forums has led me to a couple of preliminary things that I have checked, clearing the code each time (base timing wire connection, tight plug wires on the cap, "tapping" on the ECM).
My question is this, in the collective forum opinion, what the hell happened here? And what do I do from here?
Melting Slicks
Joined: Nov 2000
Posts: 3,388
Likes: 1
From: X
Re: Code 42 Help (toejam)
You need a timing light...hook it up and run the engine at 1800 to 2000 RPMs...Ground the Diagnostic terminal and note the timing ...It should change...If it changes EST circuit is ok...If it doesn't change you may have a short in a wire or a bad HEI module...There are tests you can do to check it ...but its cheap enough to just change it.
Le Mans Master
Joined: Dec 1999
Posts: 8,540
Likes: 1
From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Code 42 Help (toejam)
You can also check the tan/black wire at the ecm using a DVM. See what the voltage is. All these tests with car running.
If 5V you will need to borrow a dwell meter from some old guy to test. You hook the dwell meter to the white est wire (use 4 cly scale): if it reads 0* or 90* the est is bad. If it reads anything else ecm may be bad.
If 0V found on tan/black at ecm then disconnect the timing connector behind the MC on the firewall. If voltage at ecm continues to be 0V check the wire out and if it's good ecm may be bad. If voltage changes to 5V with the timing connector apart, inspect tan/black wire all the way back to the ignition module. If the wire is OK the est module is likely bad.
If 5V you will need to borrow a dwell meter from some old guy to test. You hook the dwell meter to the white est wire (use 4 cly scale): if it reads 0* or 90* the est is bad. If it reads anything else ecm may be bad.
If 0V found on tan/black at ecm then disconnect the timing connector behind the MC on the firewall. If voltage at ecm continues to be 0V check the wire out and if it's good ecm may be bad. If voltage changes to 5V with the timing connector apart, inspect tan/black wire all the way back to the ignition module. If the wire is OK the est module is likely bad.
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Joined: May 2001
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From: Royal Oak, MI
Re: Code 42 Help (PeteL)
If it doesn't change you may have a short in a wire or a bad HEI module...There are tests you can do to check it ...but its cheap enough to just change it.
You can also check the tan/black wire at the ecm using a DVM.
If voltage changes to 5V with the timing connector apart, inspect tan/black wire all the way back to the ignition module. If the wire is OK the est module is likely bad.
Thanks for the replies, I will likely be doing some of this investigative work tomorrow and will post the results to this thread.
Advanced
Joined: Dec 2001
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From: Hannibal, Missouri
Re: Code 42 Help (toejam)
I've got the same problem. 84, 114,000 miles, less that 1500 miles on tune up(plugs,wires dist. cap,). Started it up one day, check engine light(code 42) came on about five minutes after I started driving it. The light comes and goes but now it runs like crap, even when the light is out. Missing pretty bad and running rough. Any idea what causes this? I guess its back to the shop. I just hope it is a inexpensive(yea right) fix.
Le Mans Master
Joined: Dec 1999
Posts: 8,540
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From: And on the fifth day, subpoenas were served to Obama senior staff
Re: Code 42 Help (toejam)
The electronic spark timing module (well part) is inside the distributor. I think they are under $40.
How does the car run?
How does the car run?
Thread Starter
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Joined: May 2001
Posts: 61
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From: Royal Oak, MI
Re: Code 42 Help (PeteL)
The electronic spark timing module (well part) is inside the distributor. I think they are under $40.
How does the car run?
How does the car run?
(Edit) OK, I give. What is the difference between the ignition module and the EST module?
[Modified by toejam, 12:40 PM 4/7/2002]
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Thread Starter
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Joined: May 2001
Posts: 61
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From: Royal Oak, MI
Re: Code 42 Help (Oh My)
Not on my 87..for reference..its right above the blower motor on the pass. side. connector is the same pigtail used for dist. terminal board.
