DTC 43

Flowchart Code 43:

Wiring Diagram:

CIRCUIT DESCRIPTION
The knock sensor is used to detect engine detonation and the Electronic Control Module (ECM) will retard the electronic spark timing based on the signal being received. The circuitry within the knock sensor causes the ECM 5 volts to be pulled down so that, under a no knock condition, Circuit (CKT) 496 would measure about 2.5 volts. The knock sensor produces an A/C signal which rides on the 2.5 volts DC. The amplitude and signal frequency is dependent upon the knock level.

If CKT 496 becomes open or shorted to ground, the voltage will either go above 4.8 volts or below 0.64 volt. If either of these conditions are met for about 10 seconds, a Code 43 will be stored.


TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. This step determines if conditions for Code 43 still exist (voltage on CKT 496 above 4.8 volts or below 0.64 volt). The system is designed to retard the spark 15 ° if either condition exists.

2. The ECM has a 5 volts pullup resistor, which applies 5 volts to CKT 496. The 5 volts signal should be present at the knock sensor terminal during these test conditions.

3. This step determines if the knock sensor resistance is 3300 to 4500 ohms the sensor is OK.

4. If CKT 496 is not open or shorted to ground and the voltage reading is below 4 volts, the most likely cause is an open circuit in the ECM. It is possible that a faulty Mem-Cal could be drawing the 5 volts signal down, and it should be replaced, if a replacement ECM did not correct the problem.

DIAGNOSTIC AIDS
Check CKT 496 for a potential open or short to ground. Also, check for proper installation of MEMCAL. Refer Diagnosis by Symptom / Intermittents. - Intermittent Malfunctions