Code 43 - Electronic Spark Control (ESC): Notes

Electronic spark control is accomplished with a module that sends a voltage signal to the ECM. As the knock sensor detects engine knock, the voltage from the ESC module to the ECM drops, and this signals the ECM to retard timing. The ECM will retard the timing when knock is detected and rpm is above 900 rpm.

A Code 43 means the ECM has low voltage at circuit No. 485 terminal "B7" for longer than 5 seconds with the engine running or the system has failed the functional check.

This system performs a functional check once engine is started up to check the ESC system. To perform this test the ECM will advance the spark when coolant is above 194°F (95°C) and at a high load condition (near WOT). The ECM then checks the signal at circuit No. B7 to see if a knock is detected. The functional check is performed once per start up and if knock is detected when coolant is below 194°F (95°C), the test has passed and the functional check will not be run. If the functional check fails, the "SERVICE ENGINE SOON" 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 the "SCAN" tester will always display "YES". 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 the 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, the ESC module may mistake the interference as a knock signal.
6. This checks the ground circuit to the module. An open ground will cause the voltage on circuit No. 485 to be about 12 volts which would cause Code 43 functional test to fail.
7. Applying 12 volts to circuit No. 496 with a test light should generate a knock signal. This will determine if the ESC module is operating correctly.