Code 43 - Electronic Spark Control (ESC)

Code 43 indicates that the ECM has seen low voltage at circuit 485 (terminal B7) in ECM AB connector for longer than 4 seconds with engine running. The voltage drops at terminal B7 when ESC module shuts off because it receives an engine knock signal.

This system also performs a functional check once per start-up to check ESC system. To perform this test the ECM will advance the spark when coolant is above 194°F (90°C) and throttle wide open. The ECM then checks signal at B7 to see if engine knock is detected. The functional test is performed once per start-up and if engine knock is detected, when engine coolant is below 194°F (90°C). If functional test fails, the "CHECK ENGINE" light will remain on until ignition is turned off or until a knock signal is detected.

1. This step checks to see if ECM recognizes problem.
2. This step will determine if system is functioning at this time.
3. The ESC module supplies voltage to ECM. It should always be over 6 volts, unless system is sensing engine detonation.
4. This step checks for intermittent ESC operation. If voltage is now over 6 volts, it is a faulty ESC terminal C connection or faulty ESC module.
5. This step checks for grounded ECM.
6. This step checks for open circuit.

Fig 1: Code 43, Electronic Spark Control (ESC)

Fig 2: Code 43, Electronic Spark Control (ESC)

Fig 3: Code 43 Schematic, Electronic Spark Control (ESC)