HELLO TO ALL. I'M HAVING A MAJOR ISSUE WITH MY TRUCK WHERE IMMEDIATLY AFTERABOUT 2 SECONDS FROM STARTING IT, IT SHOOTS ME THE GLORIOUS CODE 42. IT NEVER FAILS. I CAN EVEN CLEAR THE CODE AND EVERTHING BUT STILL NO MATTER WHAT STILL HAPPENS TO COME ON EVERY SINGLE TIME AFTER ABOUT TWO SECONDS AFTER TURNING IT ON. TRIED A NEW IGNITION CONTROL MODULE AND NO LUCK, TRIED NEW ECM AND NO LUCK. IT HAS A NEW DISTRIBUTOR AND ECM. CAR IS VERY DRIVEABLE BUT THAT IS ONLY BECAUSE ITS RUNNING ON BASE TIMING FROM ECM. I HAD PREVIOUSLY HAD A MAJOR ISSUE WITH THE ECM WHICH ENDED UP BEING REPLACED, SO AS I'M PUTTING THE ECM BACK IN ITS LOCATION, I DECIDED TO GO AHEAD AND REPLACE THE INSTRUMENT CLUSTER BULBS WHICH EVERY ONE WAS PRETTY MUCH BURNED OUT.SO I REPLACE THE BULBS AND SECURE THE ECM IN ITS LOCATION.. NEXT THING I FIRE IT UP AND HERE COMES A ROUGH IDLE AS WELL AS THE CODE 42 SES LIGHT. I TURN IT OFF AND TURN IT BACK ON HOPING IT WILL FIX ITS SELF AND NOTHING. IT DOES NOT IDEL ROUGH ANYMORE BUT SOMETIMES WILL SURGE (HIGH RPM TO LOW RPM)I DONT KNOW WHERE TO GO FROM HERE. ALSO ME AND MY BUDDY NEVER DISCONECTED THE BYPASS WIRE WHEN SETTING TIMING , COULD THAT BE A MAJOR ISSUE TO CAUSE THIS. BUT LIKE I SAID IT RUNS JUST FINE ONLY THING THAT AT IDLE, COLD START UP IT RUNS[X(] AS IF IT WERE ALREADY WITHIN OPERATING TEMP. (LOW RPMS). ANY SUGGESTIONS OR HELP WOULD BE GREATLY APPRECIATED. REMEMBER THIS CODE IS NOT INTERMITTENT. IT WILL COME ONEXACLTLY 2 SECONDS AFTERTRUCK HAS BEEN STARTED. PLEASE HELP...!!!!!!!!!

 

If the bypass wire was not disconnected when you set the base timing, that could definely affect things. The ECM can only compensate so much and if base timing was set while the ECM was trying to maintain the advance, you will end up out of its adjustment range. I would start there...

If that doesn't fix it, then you may be looking at a broken wire somewhere in the harness.

Oh... One last thing... Are you sure it is either A) a '92 or B) a Vin W? The CPI engine (Vin W) wasn't released until '93...

 

I KNOW ITS A 1992 GMC 4.3 V6 CPI VIN W VORTEC, LIKE I SAID I'M PRETTY MUCH STUMBLED BECAUSE THE CODE NEVER FAILS TO COME ON AFTER 2 SECONDS OF STARTING THE ENGINE. IVE LOOKED AT ALL THE WIRES FROM THE ICM TO THE ECM AND NOTHING SEEMS TO BE BROKEN, LOOSE OR GROUNDED. THANKS.

 

Have you done a continuity test on all of the wires from where they connect at the ICM and where they connect on the ECM? A wire can be broken inside and look fine on the outside.

I do not have wiring diagrams here at work with me to be able to suggest which wire may be at fault...

 

I TRIED TO DO A CONTINUITY CHECK BUT MY METER WAS NOT WORKING PROPERLY, BUT WHAT I DID GET WAS THAT ALL FOUR WIRES WERE READIN 3 WIRES FROM DITRIBUTOR TO ECM WHERE READING 0 RESISTENCE WHERE AS FOR THE BYPASS WIRE WAS SHOWING ABOUT 2-5 OHMS . SO I REMOVED THE CONNECTOR AND JUST PUT THE WIRES DIRECT AND STILL NOTHING. I HAVE NOT CHECKED FOR THE 5 VOLTS GOING TO THE BYPASS CURCUIT THOUGH.

 

As I said, I do not have the wiring schematics in front of me. But no wire should read zero ohms..

 

THANKS, LET ME KNOW IF YOU COME UP WITH ANY MORE SUGGESTIONS



JOSE!