Code 43 - ESC (Electronic Spark Control): Notes

Electronic Spark Control (ESC) is accomplished with an ESC module that sends a voltage signal to ECM. As knock sensor detects engine knock, voltage from ESC module to ECM drops and signals ECM to retard timing. The ECM will retard timing when knock is detected and engine speed is greater than 900 RPM. Code 43 means ECM has low voltage at circuit No. D10 for longer than 4 seconds with engine running or system has failed functional check. Code 43 will set when ESC input signal has been low for more than 4 seconds, or after run spark occurs for more than 4 seconds.

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 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. D10 remains low, this causes signal on circuit No. D10 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. D10 to be approximately 5 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.