DTC 43

Code 43 Wiring Diagram:

Code 43 - Electronic Spark Control (ESC) Circuit:

CIRCUIT DESCRIPTION:
Electronic Spark Control (ESC) 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 rpm is at least 900.

Code 43 means the ECM has seen low voltage at CKT 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 per start up to check the ESC system. To perform this test, the ECM will advance the spark when coolant temperature is above 95° C and at a high load condition (near WOT). The ECM then checks for a signal at CKT B7 to see if a knock has been detected.

The functional check is performed once per start-up and if knock is detected when coolant temperature is below 95° C, the 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.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. If the conditions for a Code 43 are present the "Scan" 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 at this time. 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 CKT B7 remains low this test should cause the signal on CKT B7 to go high. The 12 volts signal should be seen by the ECM as "no knock" if the ECM and wiring are OK.
4. This test will determine if the knock signal is being detected on CKT A or if the ESC module is at fault.
5. If CKT A is routed to close to secondary ignition wires the ESC module may see the interference as a knock signal.
6. This checks the ground circuit to the module. An open ground will cause the voltage on CKT B7 to be about 12 volts which would cause the Code 43 functional test to fail.
7. Contacting CKT A with a test light to 12 volts should generate a knock signal. This will determine if the ESC module is operating correctly.

DIAGNOSTIC AIDS:
Code 43 can be caused by a faulty connection at the knock sensor at the ESC module or at the ECM. Also check CKT B7 for possible open or short to ground.
See DIAGNOSIS BY SYMPTOM - NO TROUBLE CODES STORED.