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OBDI Code 42 on my 1991 Suburban

Discussion in 'GM Powertrain' started by Crawdaddy, Dec 27, 2011.

  1. Josh

    Josh Member 100 Posts

    yours runs without the module? i replaced mine last night found my cap terminals rusted beyond belief. cleaned em up slapped it all together and ran great. come out this morning to start and i had to crank forever it would fire like hit and miss. i had to use my foot to pedal it a bit. i think i wasnt either getting fuel because i was extremely low on gas or what. it doesnt run as good now but my cel light is coming and going now. i cleaned the cap with clr/sandpaper, then used alcohol wipes to clean away. i wonder if the alcohol caused moisture to rust out terminals. install was easy though. be careful on your distributor cap screws. they break easily. i broke one and had to improvise. one screw on one side and a mini c clamp on the other. its actually tighter than before. ill get a new cap/rotor soon. ill let u know on the timing wire.

    ---------- Post added at 01:58 PM ---------- Previous post was at 01:49 PM ----------

    well i found the wire it was in the truck by the blower its brown with a deep brown stripe. no change plugged in or unplugged. its like a flat sppot when it runs it idles good touch gas it will retard timing out unless u hit gas enough to get past the flat spot.
  2. Josh

    Josh Member 100 Posts

    well man my module swap went good. found out my stalling problem was a bad egr lol. went through everything including that. didnt check buy unplugging though. the module made my check engine light come and go. runs much better. if your cooler is leaking id see if its screw in slip on style or one of those all in ones. prolly just needs some thread sealer. i tried tranny stop leak on my k5 blazers cooler it was an aftermarket b ANd M hit some rocks one day and long story short the stop leak killed the turbo 400. slipped like a banana peel after about 4 weeks. the leak never stopped only got worse. u may be able to see if you can run the fluid lines into your radiator if it has the adapter holes for it. just a thought.
  3. Crawdaddy

    Crawdaddy Thread Killer Extraordinaire Staff Member 5+ Years 1000 Posts Platinum Contributor

    Yep, my truck runs fine when the computer throws the CEL for this issue. Best I can tell, it simply stops advancing the timing and reverts back to base timing, though I have not confirmed this with a timing light.

    The cooler issue is with a B&M cooler I installed a couple months ago. I just pulled a trailer for the first time since doing to upgrade and it's leaking from the bottom fitting. I'm not sure if it's leaking from the threaded part of the slip-on part where the hose slides onto the fitting. I need to pull the bumper and grill to get a good picture of what's going on there, so it's on the to-do list.
  4. Josh

    Josh Member 100 Posts

    u got lucky then. i was all over the place gettin my cel light/stalling fixed. the Ign. module swap and cleaning dizzy up made it go from always on to comes n goes. if u ask me....unplug the cel light bulb and say if it aint broke dont fix it. i had bad luck with thread tape btw i use permatex thread seal in a can that you brush on. also wait a good hour and a half to let the seal turn to a rubbery compound. i did my first tranny line and fired it up directly after. thats a no no. out came the permatex and a quart of fluid haha.
  5. Crawdaddy

    Crawdaddy Thread Killer Extraordinaire Staff Member 5+ Years 1000 Posts Platinum Contributor

    Well, this bad ignition module is catching up with me. I took the truck out last weekend and the idle's getting pretty uneven. The light also came on with just a little idling in the yard. So, I'm gonna have to get the module changed soon. I'm hoping to get an official GM module from the dealer. I'll have to order it I'm sure, but I don't want to ever have to deal with this again.
  6. LoneWolf'burban

    LoneWolf'burban Rockstar 100 Posts

    The wire is in different places on different trucks. It's tan with a black stripe and it breaks out of the wire harness for about 6" on mine with a quick disconnect in the middle. Pop apart and set timing then clip back together and let the computer do the advance and retard on timing. Check your mag coil pick up in your distributor if you have one. Ive been through three ign moduals and a new distributor. It's not the ign mod throwing the code. At least in mine. But I do have the MSD 6AL in mine and I seem to be burning through caps and rotors quick. Lots of carbon and one post keeps corroding up quick. Cyl 6 I believe. But I keep getting code 43, electronic spark control, which refers to the ign mod. You're getting code 42, electric spark timing, that goes to a different part. Most likely the mag pick up coil. Has it ever just up and died when it was hot?
  7. Crawdaddy

    Crawdaddy Thread Killer Extraordinaire Staff Member 5+ Years 1000 Posts Platinum Contributor

    It has never once died on me or failed to start, or even a long start. While I'm replacing the module, I'm also going to replace the cap and rotor since I have to pull them off to get to the module. I'm also planning on replacing the wires, plugs, and coil too. I'm going to beat this.
  8. Josh

    Josh Member 100 Posts

    I went with a acdelco myself for the igniton module. it made a huge difference. my bad module caused some idle fluctuation. id recommend a set of new cap hold down screws. mine snapped off and got stuck in the base of the distributor. if there rusty your gonna need a very small socket. screwdriver just rounded em out. also unplug your IAC and see if anything idle wise improves just incase a sensor is startin to fail on you. may help detect other coming problems.
  9. JWHUNT1972

    JWHUNT1972 New Member

    Intermittant is the key word.

    Hi Guys I just wanted to say a little from my experience of troubleshooting an intermittant code 42. I have a 92 chevy with a 4.3L. when it runs right its a peach but when it acts crazy its sluggish and has detonation at RPM over 400. I found its either a bad ground or a bad wire in the EST circuit. when its cold i generally dont have an issue but when things warm up i get a knock. Connections loosen and moisture plays a part. I used an ohm meter to check each length of wire fron the ICM to the ECM. when you ohm the wires if there good you should get a 0.00 ohm reading. make sure you check for Ohms and not just continuity. If you find a wire that measures something different that just could be the problem. Happy trouble shooting J.W.
    P.S. make sure ya have a good connection i took the wire ends out of the plugs and connected aligator clips to them then reformed the terminal to pake sure i had a good tight connection in the terminal connection.
  10. Crawdaddy

    Crawdaddy Thread Killer Extraordinaire Staff Member 5+ Years 1000 Posts Platinum Contributor

    I replaced the module almost a year ago and haven't had the code since. I'd say the ignition module was my issue.

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