Code 43 - Electronic Spark Control (4.3L Only)
Code 43 says Electronic Spark Control (ESC) retard signal has been seen by ECM for too long. When voltage at Terminal "L" at the ECM is low, spark is retarded. Normal voltage in non-retard mode is about 7.5V or more.
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- Normal voltage would be over 7.5 volts. If 7.5 volts is present at Term. "L", the reason for a Code 43 is a poor connection to ECM or faulty ECM.
- Over 6 volts indicates an overly sensitive knock sensor or controller, or noise in engine that fools the knock sensor.
- Checks for grounded ECM.
- This test checks for an open wire between the ESC and ECM. More than 6 volts at Term. "C" of ESC indicates an open to Term. "L" of ECM.
- Checks for proper 12V ignition source to ESC Term. "B".
- Checks to see if spark retard is due to engine knock or a faulty knock sensor. If spark advances when knock sensor is disconnected, fault is result of engine "noise" or sensor.
- Checks to see if spark retard is due to a faulty ESC controller or "noise" on ESC to-knock sensor wire. If spark advances when terminal "E" is removed from connector, check for improper routing of knock sensor signal wire.