Code 42
- Thread starter gmfty
- Start date
Ty0279
Historically Significant
Re: Code 42
CODE 42
ELECTRONIC SPARK TIMING (EST) CIRCUIT
4.3L TURBO (VIN Z) SYCLONE AND TYPHOON (PORT)
Circuit Description:
The ignition module sends a reference signal (CKT 430) to the ECM when the engine is cranking. While the engine speed is under 400 rpm, the ignition module will control ignition timing. When the engine speed exceeds 400 rpm, the ECM applies 5 volts to the bypass line (CKT 424) to switch the timing to ECM control (EST CKT 423).
When the system is running “ON” the ignition module, that is, no voltage on the bypass line, the ignition module grounds the EST signal. The ECM expects to see no voltage on the EST line during this condition. If it sees a voltage, it sets Code 42 and will not go into the EST mode. When the rpm for EST is reached (about 400 rpm), voltage will be applied to the bypass line, the EST should no longer be grounded in the ignition module, so the EST voltage should be varying. If the bypass line is open or grounded, the ignition module will not switch to EST mode, so the EST voltage will be low and Code 42 will be set. If the EST line is grounded, the ignition module will switch to EST but, because the line is grounded, there will be no EST signal. A Code 42 will be set.
CODE 42
ELECTRONIC SPARK TIMING (EST) CIRCUIT
4.3L TURBO (VIN Z) SYCLONE AND TYPHOON (PORT)
Circuit Description:
The ignition module sends a reference signal (CKT 430) to the ECM when the engine is cranking. While the engine speed is under 400 rpm, the ignition module will control ignition timing. When the engine speed exceeds 400 rpm, the ECM applies 5 volts to the bypass line (CKT 424) to switch the timing to ECM control (EST CKT 423).
When the system is running “ON” the ignition module, that is, no voltage on the bypass line, the ignition module grounds the EST signal. The ECM expects to see no voltage on the EST line during this condition. If it sees a voltage, it sets Code 42 and will not go into the EST mode. When the rpm for EST is reached (about 400 rpm), voltage will be applied to the bypass line, the EST should no longer be grounded in the ignition module, so the EST voltage should be varying. If the bypass line is open or grounded, the ignition module will not switch to EST mode, so the EST voltage will be low and Code 42 will be set. If the EST line is grounded, the ignition module will switch to EST but, because the line is grounded, there will be no EST signal. A Code 42 will be set.
QUICK STORM
B.A.M.F. BMW Tech
Re: Code 42
module location is under the distributer cap. yes it can be replaced and should be part of regular maintenance. make sure when you remove the old one that you clean off the contact points between the module and distributer, and be sure to use a liberal amount of the supplied silicone, this silicone helps transfer heat away from the ignition module. i recommend replacing the cap and rotor(ac delco), wires(taylor or msd), spark plugs(ngk ur6) and the O2 sensor(ngk). also remove both ecm fuses to reset the fuel learning curve. HTH:tup:
gmfty said:
module location is under the distributer cap. yes it can be replaced and should be part of regular maintenance. make sure when you remove the old one that you clean off the contact points between the module and distributer, and be sure to use a liberal amount of the supplied silicone, this silicone helps transfer heat away from the ignition module. i recommend replacing the cap and rotor(ac delco), wires(taylor or msd), spark plugs(ngk ur6) and the O2 sensor(ngk). also remove both ecm fuses to reset the fuel learning curve. HTH:tup:
SY2932
Administrator
Re: Code 42
Before you replace anything, check to make sure that the ESC wire is connected. There have been instances where is was a simple matter of it getting disconnected somehow:
"The ESC Electronic Spark Timing "tan wire with a black stripe" that everyone can't find when attempting to set their timing (s-series). Wire is under the carpet on the passenger side below the heater box. It is disconnected to set the timing, then reconnected."
If the ignition module turns out to be the culprit, the part numberfor it is 1048-2827. Usually when an ignition module goes bad, your truck won't run at all.
Before you replace anything, check to make sure that the ESC wire is connected. There have been instances where is was a simple matter of it getting disconnected somehow:
"The ESC Electronic Spark Timing "tan wire with a black stripe" that everyone can't find when attempting to set their timing (s-series). Wire is under the carpet on the passenger side below the heater box. It is disconnected to set the timing, then reconnected."
If the ignition module turns out to be the culprit, the part numberfor it is 1048-2827. Usually when an ignition module goes bad, your truck won't run at all.
qbnkiller
Conflaguration Specialist
Re: Code 42
Also, I have been fighting this very issue for 2 years now.....changed the ECM, ignition module 4 times, checked/replaced wiring....couldn't find it. Finally, I went to Advanced auto parts and bought a new OEM distributor.....problem solved. Looking at the dist, it didn't look bad...no excessive play in the shaft.....no bad teeth.....decent magnetic resistance. But I changed it and it's 1000% better now.
HTH
Also, I have been fighting this very issue for 2 years now.....changed the ECM, ignition module 4 times, checked/replaced wiring....couldn't find it. Finally, I went to Advanced auto parts and bought a new OEM distributor.....problem solved. Looking at the dist, it didn't look bad...no excessive play in the shaft.....no bad teeth.....decent magnetic resistance. But I changed it and it's 1000% better now.
HTH
Couger1968
Dazed and Confused
Re: Code 42
I am resurrecting an old thread. What would cause my truck to make this code when it runs great most of the time. It will usually happen when it is cold. It seems to be happening more frequently. I clear the code and it might be fine for a few weeks or a few days. It usually misses a few times and kicks the code then runs crappy untiI clear it. Thanks
I am resurrecting an old thread. What would cause my truck to make this code when it runs great most of the time. It will usually happen when it is cold. It seems to be happening more frequently. I clear the code and it might be fine for a few weeks or a few days. It usually misses a few times and kicks the code then runs crappy untiI clear it. Thanks
IGottaSy
Active member
Re: Code 42
On my truck, code 42 will appear upon deceleration after normal driving. It's also sporadic. I have tried 3 different distributors and at least 2 new ignition modules. I have verified the brown wire isn't loose at the connections. It usually clears itself as soon as the truck starts to move after coming to a stop light. Very seldom, it will stay on and clears at next key cycle. Searched but haven't found any old info on this. Other than this, the truck has a nice kick and surprises even the suped up, filthy, un apologetic diesel soot lovers.
On my truck, code 42 will appear upon deceleration after normal driving. It's also sporadic. I have tried 3 different distributors and at least 2 new ignition modules. I have verified the brown wire isn't loose at the connections. It usually clears itself as soon as the truck starts to move after coming to a stop light. Very seldom, it will stay on and clears at next key cycle. Searched but haven't found any old info on this. Other than this, the truck has a nice kick and surprises even the suped up, filthy, un apologetic diesel soot lovers.