Code 42
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Joined: Aug 2003
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From: Soddy Daisy TN
Code 42
I just got my engine back together (1989 L98) and running and things seem to be going well. I have had no "check engine" lights at all while driving the car for the last 2 days. I have my timing set at 6 degrees btdc with the by-pass connector apart. So for the heck of it I plug in my code scanner and get a code 42. First question, why no "check engine" light? Second, what do I do now? 
Team Owner
Joined: Jul 2004
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From: Hartford WI
Code 42- This code will be set when the engine is running at 600 rpm or greater, and there is no pulse on the white wire from the ecm to the ignition module for more than 200ms (milliseconds). Common causes for this code include bad connections, frayed wiring, or broken wires such as the tan/black (ecm pin D5) purple/white( ecm pin B5) or white wire (ecm pin D4). Check your wiring carefully along with the connections back to the ecm.
This is copied from a F-Body board but it applies to you, I believe. If you set the timing, you would disconnect the tan/black wire, set the distributor and then reconnect it. I suspect that it is sitting waiting for a certain number of starts to occure before it clears itself out. I would beleive it is considered "intermitten". Clear the code and see if it reappears.
This is copied from a F-Body board but it applies to you, I believe. If you set the timing, you would disconnect the tan/black wire, set the distributor and then reconnect it. I suspect that it is sitting waiting for a certain number of starts to occure before it clears itself out. I would beleive it is considered "intermitten". Clear the code and see if it reappears.
Team Owner
Joined: Sep 2002
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From: OBAMA IS HITLER
Originally Posted by aklim
It will come back if you disconnect the wire to set the timing again. Just that you were too busy to notice that it set the code and when you reconnected it, the light went off.
I learned this as well....disconnecting the tan/balck EST wire - necessary for ignition timing check/adjust - always sets a code 42. SOP is to disconnect the neg (-) batter terminal for at leats 30 seconds to clear the code.
Le Mans Master
Joined: Dec 2000
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From: San Diego, Ca
To keep your radio presets, just disconnect the ECM feed at the battery. It's the same type of connector as the timing wire. If you're smog testing checks timing (they do here in CA), remember to clear the code afterwards. That way you won't be wondering where it came from when you happen to run a scan months down the road.
