CODE 42
Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.
During cranking, the timing is controlled by the ignition module
while the ECM monitors the engine speed. When the engine speed exceeds
400 RPM, the ECM sends a BYPASS signal to the ignition module which
switches the timing to ECM control. The ECM calculates what the timing
should be then "tells" the ignition module via the EST circuit.
An open or ground in the EST circuit will stall the engine and set a
Code 42. The engine can be re-started but it will run on ignition
module timing.
The conditions for setting this code are:
- System in BYPASS mode but the ignition module is still controlling timing
- or -
- Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.
Typical causes for this code include:
1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM
Thank you for using fixya and keep us posted
1992 gmc 1500 lakes power some times replaced esc module and hole distributer and still get code 43 woundering what else it could be?
engine almost stalls when i take off. it keeps advancing my timing after i just reset it. replaced distributor, plugs wires, egr valve. when i go down the road it spits codes 42 and 43. and runs like **** all the time. COULD THIS BE MY KNOCK SENSOR OR ECM??????
×