P033B Knock Sensor 4 Circuit Voltage, Bank 2
Content
P033B Knock Sensor 4 Circuit Voltage, Bank 2
OBD-II DTC Datasheet
Knock Sensor 4 Circuit Range / Performance (Bank 2)
What does this mean?
This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.
Knock sensors are used to detect engine pre-knock (knock or horn). The knock sensor (KS) is usually two-wire. The sensor is supplied with a 5V reference voltage and the signal from the knock sensor is fed back to the PCM (Powertrain Control Module). This DTC applies to row 4 knock sensor # 2, refer to the specific vehicle service manual for your location. Bank 2 is always on the side of the engine that does not contain cylinder # 1.
The sensor signal wire tells the PCM when knocking occurs and how severe it is. The PCM will slow down ignition timing to avoid premature knock. Most PCMs are capable of detecting spark knock tendencies in an engine during normal operation.
If the PCM determines that the knocking is abnormal or that the noise level is abnormally high, P033B may be set. If the PCM determines that the knock is severe and cannot be cleared by slowing the ignition timing, P033B may be set. Be aware that knock sensors cannot distinguish between knock and pre-knock or engine malfunction.
symptoms
Symptoms of a P033B trouble code may include:
- MIL Illumination (Malfunction Indicator)
- Sound knock from the engine compartment
- Engine sound when accelerating
reasons
Possible causes of the P033B code include:
- Knock sensor circuit shorted to voltage
- The knock sensor is out of order
- Knock sensor connector damaged
- Knock sensor circuit open or shorted to ground
- Moisture in the knock sensor connectors
- Incorrect fuel octane
- PCM out of order
Possible solutions
If engine knocking is heard, first correct the source of the mechanical problem and then recheck. Make sure the engine has been running with the correct octane rating. Using fuel with a lower octane number than specified may cause ringing or premature knock, and may also cause the P033B code.
Disconnect the knock sensor and check the connector for water or corrosion. If the knock sensor has a seal, check that the coolant from the engine block does not contaminate the sensor. Repair if necessary.
Turn the ignition to the run position with the engine off. Make sure 5 Volts is present at the KS # 4 connector. If so, check the resistance between the KS terminal and engine ground. To do this, you will need a vehicle specification. If the resistance is not correct, replace the knock sensor. If the resistance is normal, reconnect the KS and let the engine idle. With a scan tool in the data stream, observe the KS value. Does this mean that there is a knock at idle? If so, replace the knock sensor. If the knock sensor does not indicate knock at idle, tap the engine block while observing the knock signal. If it does not show a signal corresponding to the taps, replace the knock sensor. If so, make sure the knock sensor wiring is not routed near the ignition wires. If the knock sensor connector did not have 5 volts when disconnected from KOEO (engine off key), return to the PCM connector. Switch off the ignition and secure the 5V reference wire of the knock sensor in a location that is easy to repair (or disconnect the wire from the PCM connector). Use KOEO to check for 5 volts on the PCM side of the cut wire. If 5 volts is not present, suspect a faulty PCM. If 5 volts is present, repair the short on the 5 volt reference circuit.
Since the reference circuit is a common circuit, you need to test all the motor sensors that are supplied with a 5 V reference voltage. Turn off each sensor in turn until the reference voltage returns. When it returns, the last connected sensor is the one with a short circuit. If neither sensor is shorted, check the wiring harness for a short to voltage on the reference circuit.
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