Code 43: Electronic Spark Control (ESC): Notes

The ECM will retard timing when knock is detected and engine speed is greater than 900 RPM. To check the ESC system, a functional check is performed by the ECM each time engine is started. To perform this test, the ECM will advance the spark when coolant temperature is greater than 194°F (95°C) and under a high load condition (near WOT). The ECM then checks the signal on circuit No. 485 to see if a knock is detected. If knock is detected when coolant temperature is less than 194°F (95°C), test has passed and the functional check will not be run. If the functional check fails, the "CHECK ENGINE" light will remain on until ignition is turned off or until a knock signal is detected.

1. If the conditions for a Code 43 are present, "Scan" tester will display the amound of timing retard. There should not be a knock at idle unless an internal engine problem or a system problem exists.
2. This test will determine if the system is functioning. Usually, a knock signal can be generated by tapping on the right exhaust manifold. If no knock signal is generated, try tapping on block close to the area of the sensor.
3. Because Code 43 sets when the signal voltage on circuit No. 485 remains low, this test should cause the signal on circuit No. 485 to go high. If ECM unit and wiring are okay, the 12-volt signal should be seen by the ECM as "no knock".
4. This test will determine if the knock signal is being detected in circuit No. 496 or if the ESC module is at fault.
5. If circuit No. 496 is routed too close to secondary ignition wires, ESC module may see induced interference as a knock signal.
6. This checks the ground circuit to the module. An open ground circuit will cause the voltage on circuit No. 485 to be about 12 volts, which would cause Code 43 functional test to fail.
7. This will determine if the ESC module is operating correctly. Applying 12 volts to circuit No. 496 with a test light should generate a knock signal.