Technical Description of OBD-II Trouble Code
The circuit range/performance of Knock Sensor 4 (Bank 2)
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
Knock sensors are utilized to detect engine pre-detonation, also known as engine knock or ping. The knock sensor (KS) typically consists of two wires. The sensor receives a 5-volt reference and sends a signal back to the PCM (powertrain control module). In the case of this DTC, it pertains to the #4 knock sensor on bank 2. Refer to the vehicle’s specific service manual to locate the sensor. Bank 2 always refers to the side of the engine that does not contain cylinder #1.
The sensor signal wire informs the PCM about the occurrence of a knock and its severity. The PCM will adjust the spark timing to prevent pre-detonation. Most PCMs have the capability to learn spark knock patterns during normal engine operation.
If the PCM determines that the knock is abnormal or the noise level is unusually high, it may trigger the P033B code. If the PCM detects severe knock that cannot be resolved by retarding the spark timing, the P033B code may be set. It is important to note that knock sensors cannot differentiate between knock caused by pre-detonation and knock caused by engine issues.
Symptoms
The symptoms associated with the P033B DTC may include:
Causes
The potential causes of the P033B code are:
Possible Solutions
If an engine knock is audible, it is important to address the mechanical issue first and then retest. Ensure that the engine has been filled with the correct octane fuel, as using lower octane fuel than specified can lead to pinging or pre-detonation, potentially causing the P033B code.
Disconnect the knock sensor and inspect the connector for water or corrosion. If the knock sensor has a seal, check for any coolant from the engine block that may be affecting the sensor. Repair as necessary.
With the engine off, turn the ignition to the run position and verify the presence of 5 volts at the KS #4 connector. If 5 volts are present, check the resistance between the KS terminal and engine ground, referring to the vehicle’s specifications. If the resistance is outside the specified range, replace the knock sensor. If the resistance is normal, reconnect the knock sensor and idle the engine. Use a scan tool to observe the KS value in the data stream. Does it indicate the presence of a knock at idle? If so, replace the knock sensor. If the knock sensor does not show any knock at idle, tap on the engine block while monitoring the knock signal. If the signal does not correspond with the taps, replace the knock sensor. If it does, ensure that the knock sensor wiring is not routed near ignition wires. If there was no 5 volts present at the knock sensor connector while unplugged with the key on engine off (KOEO), return to the PCM connector. Turn the ignition off and cut the knock sensor 5-volt reference wire in a location that is easy to repair (or remove the wire from the PCM connector). With the KOEO, check for 5 volts on the PCM side of the cut wire. If 5 volts are not present, suspect a faulty PCM. If 5 volts are present, repair any short in the 5-volt reference circuit.
Since the reference circuit is shared, it is necessary to check all engine sensors that receive a 5-volt reference. Unplug each sensor one at a time until the reference voltage returns. The last sensor that is plugged in before the voltage returns is the shorted sensor. If none of the sensors are shorted, inspect the wiring harness for any short to voltage on the reference circuit.
