Mal code 42 - weird

87-WE2

Back in business!!
Joined
May 17, 2011
OK - so I got my new TT5.7 and 60's in. Runs smooth. Stumble at lock-up in 4th is gone. 0.0 KR all the time. Never got any knock at all after the new chip & injectors. The coolant temps were even cooler. WHEW!! Glad to be rid of the ATR Pit Bull. Enjoyed it so much I drove for 3 hours on Sat night just enjoying a smooth ride. But the car's a little weaker than before, so I figured it's time to do a little tuning.

Coolant temps were around 165 (which I find good), and o2s were high - about 850 @ WOT in 3rd. BLM's were a little low at 118-120. All this indicates to me that it's a little rich, so I pulled 1.6% WOT fuel out in all gears (#01 set to 126). Temps came up to about 175 and BLM hit 126 and 02s leveled out at 800. I figured I'm there. Left #01 alone.

Still haven't hit any K$ at all (well, OK - 1.2 KR, but on a downshift from 3-2, but it only happened once). I figure it's time to start playing with timing a little to try & tickle the knock sensor. I set #03 (1&2 timing) to 134 (2.1 advance). I also set #04 (3&4 timing) to 131 (1.1 advance). Still no KR in 1 or 2, but a consistent 0.2 KR in 3rd. I didn't have the balls to go fast enough to see what would happen in 4th. By that time, you're going pretty fast!! I figure I'm there in 3-4, but still need to work on 1&2 timing. Car feels great - almost like before with the Pit Bull chip that had too much timing & lots of KR.

Set #03 (1&2 timing) to 137 (3.2 advance). Still 0.0 KR in 1&2, so I figure go up a degree at a time till I hit the sweet spot. I bump #03 (1&2 timing) to 139 (3.9 advance). Crank it up, put it in gear, TURN ON THE HEADLIGHTS and SES comes on! Thought it might be an electrical fluke, so I turned the lights off. SES stays on. Well crap - I check & mal code 42 which is EST circuit failure (ignition module to ECM). Huh. WTF? I know i can unplug the orange wire & clear the code, but my fuel and timing settings disappear. Not knowing what this code means, I thought it might be unsafe to drive, so I cleared the code. I put the settings back to my "tuned settings (I had written them down), start her up, pull away, hit the headlights, and BOOM - SES light on again code 42. WTF? I noticed that it was weaker than before, but I didn't know anything about code 42. So I reset the ECM again, leave the chip at the default settings and drive around for about 30 min. trying to pull another 42. Didn't do it. I only get the code 42 when I play with my chip settings.

So I come home & do a little research on code 42. I learn that when this code is thrown, the ECM Spark is disabled and the car runs on the ign module timing. That explains the weaker engine feel.

Anyone have any ideas? what could cause a code 42, but only when timing & fuel has been modified? If I had a bad pin on ECM or ign module, wouldn't this code be thrown regardless of the timing & fuel settings. I have driven the car for a total of 4 1/2 hrs. on default settings & no code. A full tank of gas & no code. The only connection i can see with the 42 is when I went to 139 on the 1st & 2nd gear timing advance.

I have a brand new coil pack from Kirban (I bought a Delco first for $140, but took it back when I found it was made in China), new High Boost plug wires custom made by blackgn1, new Autolite plugs (not Chinese like Delco's).

I will be playing with this thing more, but will go about it systematically as before. I think I'll start by advancing timing to 137 in 1st & 2nd only to see if I get the 42. If not, bump to 139 & see if I get it. If not, add timing to 3-4 and so forth. Maybe it's just a weird combination??

Is my tuning theory even correct? I've confused myself.
 
I was getting a code 42 and a flashing ses light with a stumble, crank sensor was out of wack used 2 pieces of plastic 2 liter bottle material on each side of blade on damper and crank sensor slots, so far so good.
 
Thanks for the response. I've got no stumble or anything, but will check the crank sensor.

Just seems weird to me that I only get the code when I advance the timing.
 
I got a Code 42 occasionally, ended up disconnecting and reconnecting everything between the ECM and C3I. Haven't had any problems since. I have no idea if a connection was loose, or the "fix" was a fluke, but it might be worth looking at (especially if you've been messing around with the ECM or chip).

No idea why it's correlated to your tuning... good luck!
 
Jumping in to share my experience. Similar issues last summer. Stumbling, misfiring, "soft code" 42 by which I mean the code would not remain but reset itself. MY problem was a bad ECM. Many possibilities and many folks on this board with more knowledge than me but that turned out to be the fix for my car at that time. Good luck.

Dean
 
Try to get it to happen again and take note of whether or not your changed settings go back to default before you do a clear. If they return to default settings you are loosing ground or power. Mine ended up being the power wire at the battery. The fusible link. It was my Powerlogger that enabled me to find the problem.
 
Try to get it to happen again and take note of whether or not your changed settings go back to default before you do a clear. If they return to default settings you are loosing ground or power. Mine ended up being the power wire at the battery. The fusible link. It was my Powerlogger that enabled me to find the problem.

Damn good idea! I don't know why I checked it, but I did check it before I cleared the code. My settings were in there. I will check on the power cables tonight.

BTW to all - I posted this same thread in the Chips area and I've got a couple responses that I'll try as well. One of them was from Eric who recommended keying off for 10 seconds after changing settings on the chip. I will try that tonight. Just trying to help in case anyone else may be having a similar issue.
 
Damn good idea! I don't know why I checked it, but I did check it before I cleared the code. My settings were in there. I will check on the power cables tonight.

BTW to all - I posted this same thread in the Chips area and I've got a couple responses that I'll try as well. One of them was from Eric who recommended keying off for 10 seconds after changing settings on the chip. I will try that tonight. Just trying to help in case anyone else may be having a similar issue.
If your settings stay you're not loosing 12 volts or ground.
 
PROBLEM RESOLVED!!!!

Based on advice from Eric, after changing settings in the chip and keying off, leave the key off for 10 seconds. I did this and all is well. I duplicated my settings above that were throwing a code, keyed off, waited 10 seconds (maybe a little more), started, and drove.

Special thanks to Eric Marshall for truly superior service after the sale. I may start a petition to officially change his name to "Wizard".

Just to brag on him a little more he also diagnosed a loose connection on my alternator from about 1000 miles away without ever seeing the car!!
 
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