Powertrain Controls - ECM/PCM

DTC 43 Knock Sensor Circuit:

Knock Sensor Wiring Circuit:

CIRCUIT DESCRIPTION:
Knock Sensor (KS) is connected to a module that sends a voltage signal to the PCM. As the knock sensor detects engine knock, the voltage from the KS module to the PCM drops, and this signals the PCM to retard timing. The PCM will retard the timing when knock is detected if: coolant temperature is above 35°C, RPM is at least 1500 or vehicle speed is greater than 10 mph, and battery voltage is at least 9 volts.

DTC 43 means the PCM has seen low voltage at CKT 485 terminal "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 KS system. To perform this test, the PCM will advance the spark up to 200. If no knock has been detected after adding 200 of advance, the system has failed the functional check. When coolant is between 90°-115°C (194°-239°F), and high load conditions are met, the PCM will then check the signal at "B7."

DTC 43 WILL SET WHEN:
The PCM detects an absence of ESC activity or too much ESC activity.

ACTION TAKEN (PCM WILL DEFAULT TO):
Knock retard will be fixed at 80 of timing retard. The MIL will become illuminated.

DTC 43 WILL CLEAR WHEN:
A current DTC 43 will clear when the PCM detects the correct signal voltage from the knock sensor module. A history DTC 43 will clear after 50 consecutive ignition key cycles without a current DTC 43 being stored.

DTC CHART TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If the conditions for a DTC 43 are present the Tech 1 scan tool 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 DTC 43 sets when the signal voltage on CKT 408 remains low this test should cause the signal on CKT 408 to go high. The 12 volts signal should be seen by the PCM as "no knock" if the PCM and wiring are OK.
4. This test will determine if the knock signal is being detected on CKT 496 or if the KS module is at fault.
5. If CKT 496 is routed too close to secondary ignition wires the KS 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 408 to be about 12 volts which would cause the DTC 43 functional test to fail.
7. Contacting CKT 496 with a test light to 12 volts should generate a knock signal. This will determine if the KS module is operating correctly.

DIAGNOSTIC AIDS:
DTC 43 can be caused by a faulty connection at the knock sensor at the KS module or at the PCM. Also check CKT 408 for possible open or short to ground.

Refer to "Intermittents" in "Diagnosis By Symptom." - Intermittent Malfunctions

Use of premium fuel is not recommended and can contribute to a false DTC 43.