What causes a GM engine to set code 42?

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.

What happens when you set a code 42?

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 code 42 are:

What is the Code 42 on a Cadillac?

Another code that seems to bring about quite a bit of confusion is code 42 found on most G.M. vehicles except some Cadillac’s and other E-body vehicles that use code (E) 23 as a flag for an Electronic spark timing (EST) circuit fault. The EST circuit has been on G.M. vehicles for quite a few years.

What does trouble code 42 mean on spark timing?

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

What are the trouble codes for a corvette?

31 LCD data circuit shorted to battery or CCM internal open 33 Data clock circuit shorted to battery or CCM internal open circuit 35 Data strobe circuit shorted to battery or CCM internal open circuit 36 Data strobe circuit open or shorted to ground 37 M clock circuit shorted to battery or CCM internal open circuit

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

What does trouble code 23 on GM W-body ECM mean?

CODE 23. Trouble Code 23 indicates that the Manifold Air Temperature (MAT) sensor or Intake Air Temperature (IAT) is reading lower than expected. When the air is cold, the thermistor has a high resistance, which falls as the air charge warms. Low readings thus indicate possible open circuits in MAT circuit.

What are the trouble codes for a GM car?

P1245Intake Plenum Switchover Valve P1250Early Fuel Evaporation Heater Circuit P1257Supercharger System Overboost P1258Engine Coolant Overtemperature – Protection Mode Active P1260Last Test Failed SCC Or Theft Detected, Vehicle Immobilized P1270Accelerator Pedal Position Sensor A/D Converter Error P1271APP Sensor 1-2 Performance

When does an ECM not set code 42?

Circuit Description. When the system is running on the Ignition Module, that is, no voltage on the by-pass 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.

What are the error codes for service engine light?

31. Low voltage at manifold absolute pressure sensor OR Fuel injector OR Park or neutral switch OR CAM diagnostic OR Governor malfunction OR Wastegate overboost OR Wastegate eletrical signal open or shorted to ground 32. 33. 34. 35. 36. 37. 38.

What’s the diagnostic code for a s 10 engine?

F for at least 4 seconds after the engine had been running for 2 seconds. 16 – System voltage high – Charging system voltage was either below 9 volts or above 17 volts for 10 seconds.

What is the function of the automatic shutdown relay?

One of these components is the automatic shutdown relay, commonly referred to as the ASD relay. The ASD relay is responsible for supplying switched 12-volt power to the vehicle’s injectors and ignition coils, allowing them to provide fuel and produce spark.