I have a code 42 that has popped up on my 85. I understand that code 42 has to do with the est. I did research and found the article below listed as a quote. I checked the bypass signal wire for +/- 5VDC as listed below and it showed NO VOLTAGE at all. If my electronic spark control module is bad, why would it still raise the timing level after the initial timing was set? I know that I set the timing at 6* and I checked it after I plugged the EST wire in and it was above 6* and seemed to be working. What else could be wrong?





(QUOTE)..........About Code 42; the EST module in the HEI distributor grounds the "EST Bypass signal" which is generated by the ECM, until the engine has revved past 400rpms. While the signal is grounded the EST module has control over ignition timing. After 400rpms the EST module doesn't ground the signal, and the ECM has control over the EST module and timing control.

As said, check all wiring going to the distributor; check internal Distributor connector to the EST Module. With engine off, disconnect EST Bypass signal wire next to the left side of the Brake Vacuum assist Diagram. It will be a single tan or orange wire with Weather-pack connectors. Start engine, after idle has stabilized, measure voltage on one of the two side of the Bypass signal wire. You should see +/- 5VDC, if not verify continuity of EST Bypass signal wire to ECM connector, if good, suspecting a defective ECM. If the 5VDC signal is there, replace the $37 EST Module.
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I'm going to have to go from memory here because I don't have my 85 FSM with me, but I think when you set the timing and have disconnected the EST plug to do that you will get a code (I think it might be a code 42) that you will have to clear once you are finished setting the initial timing. Is this the case here or is the code a hard code and keeps setting again after you cleared it the first time? Someone else with an FSM might need to verify this.

 

You are correct. If you set the timing and unplug the wire (as directed) this will set the code 42 on a 1985. After setting the timing and reconnecting this wire, you have to disconnect the neg terminal from the battery for 15-20 seconds then reconnect. This will clear the code. Once cleared you should be good. If it pops up again then there is a problem.

If the code resets, the "Probable cause"....Check the wiring and connectors between the ignition module and the ECM. Replace the Ignition module(**).....Replace the ECM (**).

(**)"Component replacement may not cure the problem in all cases. For this reason, you may want to seek professional advice before purchasing replacement parts." - These last two paragraphs are quotes from my Hayes manual.

 

Ok I got the code to go away because I forgot to disconnect the battery after setting the timing with the wire diconnected. So I got that code to go away. Now I only have a code 33 which is the MAF. I have replaced the MAF with one that I know works and it didnt work on the car either so I have another burn off module ordered and on the way....