What does it mean?
This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by brand/model.
Knock sensors are used to detect engine pre-detonation (engine knock or pinging). The knock sensor (KS) is typically a two-wire sensor. A 5-volt reference is provided to the sensor, and there is a signal return from the knock sensor to the PCM (Powertrain Control Module). For this DTC, it refers to knock sensor #3; refer to the vehicle-specific service manual for the specific location. If there are multiple engine banks, it is the cylinder bank that contains cylinder #1.
The sensor’s signal wire informs the PCM when a knock occurs and to what degree of severity. The PCM will retard spark timing to prevent pre-detonation. Most PCMs have the capability to learn spark knock trends in the engine during normal operation.
If the PCM determines that the knock is out of the ordinary or the noise level is abnormally high, P032B may be set. If the PCM detects that the knock is severe and cannot be eliminated by retarding spark timing, P032B may set. Keep in mind that knock sensors cannot distinguish between pre-detonation knock and engine mechanical problem noises.
Symptoms
Symptoms of a P032B DTC may include:
MIL (Malfunction Indicator Lamp) illumination
Audible knocks from the engine compartment
Engine pinging under acceleration
Causes
Potential causes of a P032B code include:
Knock sensor has failed
Knock sensor connector is damaged
Knock sensor circuit is open or shorted to ground
Knock sensor circuit is shorted to voltage
Moisture in the knock sensor connectors
Incorrect fuel octane
PCM has failed
Possible Solutions
If engine knock is audible, first correct the source of the mechanical problem, then retest. Ensure the correct fuel octane has been used in the engine. Using fuel with a lower octane rating than specified can cause knock or detonation and may trigger P032B.
Disconnect the knock sensor and check for water or corrosion in the connector. If the knock sensor has a seal, check that no engine block coolant is fouling the sensor. Repair if necessary.
Turn the ignition to the ON position with the engine off. Ensure 5 volts are present at the KS #3 connector. If so, check the proper resistance between the KS terminal and engine ground. You will need a vehicle specification for this. If the resistance is out of specifications, replace the knock sensor. If the resistance is normal, reconnect the KS and run the engine at idle. Using a scan tool in the data stream, observe the KS value. Does it indicate that a knock is present at idle? If so, replace the knock sensor. If the knock sensor shows no knock at idle, tap on the engine block while observing the knock signal. If it does not show a signal corresponding to the taps, replace the knock sensor. If it does, check that the knock sensor wiring is not routed next to ignition wires. If there were no 5 volts present at the knock sensor connector when it was disconnected with KOEO (Key On Engine Off), go back to the PCM connector. Turn off the ignition and cut the 5-volt knock sensor reference wire in an easy-to-repair location (or remove the wire from the PCM connector). With KOEO, check for 5 volts from the PCM side of the cut wire. If 5 volts is not present, suspect a faulty PCM. If 5 volts are present, repair the short in the 5-volt reference circuit.
Since the reference circuit is a shared circuit, you will need to check all engine sensors that receive a 5-volt reference. Disconnect each sensor one by one until the reference voltage returns. When it returns, the last sensor you disconnected is the shorted sensor. If no sensor is shorted, check that the wiring harness is not shorted on the reference circuit.