Powertrain Controls - ECM/PCM

DTC 43 - Knock Sensor Circuit Diagnosis:

Knock Sensor Wiring Circuit:

Circuit Description:
The knock sensor detects engine detonation and the Powertrain Control Module (PCM) retards the electronic spark timing based on the signal being received. The knock sensor produces an AC signal which is used for knock detection. The amplitude and signal frequency are dependent upon the knock level.

The PCM performs two tests on this circuit to determine if it is operating correctly.

DTC 43 Will Set When:
^ There is an indication of knock for more than 5 seconds over a 6 second interval with the engine running.
^ PCM terminal "BC13" does not indicate increasing Knock Sensor (KS) activity with engine speed.

Action Taken (PCM will default to): The Malfunction indicator Lamp (MIL) will illuminate, and the cooling fan will enable.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the conditions for the test as described above are met, DTC 43 will set and the MIL (Service Engine Soon) will be illuminated.
2. If the engines has an internal problem which is creating a knock, the knock sensor may be responding to the mechanical noise.
3. The Tech 1 scan tool displays knock sensor activity in counts, approximately 50 at idle. The counts should rise when engine speed increases or fall when engine speed decreases. This step checks knock sensor activity
4. This checks that the internal resistance of the knock sensor is within an acceptable range.
5. Check the knock sensor connection for loose terminals or corrosion. A faulty connection will set a DTC 43.

Diagnostic Aids: Check CKT 496 for a potential open or short to ground.

Also check for proper installation of the EPROM.

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

An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

Any circuitry, that is suspected of causing the intermittent complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.

Mechanical engine knock can also cause a knock sensor signal. Abnormal engine noise must be corrected before using this chart.