Code 43 - ESC (Electronic Spark Control): Notes

The ECM will retard timing when knock is detected and engine speed is greater than 900 RPM. To check ESC system, a functional check is performed by ECM each time engine is started. To perform this test, ECM advances spark when coolant temperature is greater than 203°F (95°C) and under a heavy load condition (near WOT). The ECM then checks the signal on circuit No. B7 to see if a knock is detected. If knock is detected when coolant temperature is less than 203°F (95°C), test has passed and functional check will not be run. If functional check fails, CHECK ENGINE light remains on until ignition is turned off or until a knock signal is detected.

1. If conditions for a Code 43 are present, scan tester will display YES. There should not be a knock at idle unless an internal engine problem or a system problem exists.
2. This determines if 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 sensor area.
3. Because Code 43 sets when signal voltage on circuit No. B7 remains low, this causes signal on circuit No. B7 to go high. If ECM and wiring are okay, the 12-volt signal should be seen by the ECM as a no-knock situation.
4. This determines if knock signal is detected in terminal "E" circuit or if ESC module is at fault.
5. If terminal "E" circuit is routed too close to secondary ignition wires, ESC module may see induced interference as a knock signal.
6. This checks ground circuit to ESC module. An open ground circuit causes voltage on circuit No. B7 to be approximately 12 volts, which causes Code 43 functional test to fail.
7. This determines if ESC module is operating correctly. Applying 12 volts to terminal "E" with a test light should generate a knock signal.