DTC 43

Fig. 014 - Wiring Diagram for Code 43 Electronic Spark Control (ESC):

CODE 43, ELECTRONIC SPARK CONTROL (ESC)

Code 43 means the ECM has seen low voltage at CKT 485, terminal "4" in the white ECM connector, for longer than 4 seconds with the engine running.
This voltage drops when the ESC module shuts off because it receives a knock signal.

Fig. 013 - Chart Code 43 Electronic Spark Control (ESC):

1. The ESC module supplies voltage to the ECM. It should always be over 6 volts unless the system is sensing engine detonation.
2. Checks for intermittent ESC operation. If the voltage is now over 6 volts, it is faulty ESC terminal C connection or ESC module.