DTC 43

DTC 43 Circuit Diagram:

DTC 43 Diagnostic Chart Electronic Spark Control Circuit:

CIRCUIT DESCRIPTION:

The knock sensor is used to detect engine detonation and signal the ECM to retard the tining. The circuitry within the knock sensor causes the ECM 5 volt reference to be pulled down so that under a no knock condition, BLU/WHT wire would measure about 2.5 volts. The knock sensor produces an A/C voltage which rides up on the 2.5 VDC. The amplitude and signal frequency are dependant upon knock severity.
If BLU/WHT wire becomes open or shorted to ground the voltage will either go above 3.5 volts or below 1.5 volts. If either of these conditions are met for about 5 seconds, DTC 43 will be stored.

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

1. DTC 43 sets under the following conditions:
- Coolant temperature above 90° C.
- MAT temperature above 0° C.
- High engine load, based on MAP sensor and engine rpm.
- A knock is indicated for more than 3 seconds.
- All conditions are met for at least 5 seconds.

NOTE: An audible knock should not be heard from engine. If so, repair the engine, as no knocking should be heard at idle.

2. If tapping on the engine block does not induce the signal, try tapping closer to the sensor.

3. The ECM has a 5 volt pullup resistor, which should be present at the knock sensor terminal.

4. This test determines if the knock sensor or the ECM is faulty.

DIAGNOSTIC AIDS:
Check BLU/PNK wire for a possible open or short to ground. Check for a possible mechanical fault, incorrect ignition timing and possible turbo overboost.
For intermittant CHECK ENGINE light,
Intermittant Check Procedure