P033E Knock sensor 4 circuit malfunction (bank 2)

OBD-II DTC Datasheet

Knock Sensor 4 Circuit Malfunction (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 (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although general in nature, the specific repair steps may differ depending on the brand / model.

When I ran into the stored code P033E diagnostics, it indicated that the powertrain control module (PCM) detected an intermittent knock sensor signal for the second row of engines. Knock sensor 4 may indicate a specific sensor (in a multi-sensor configuration) or indicate a specific cylinder. Bank 2 refers to the engine group that contains no number one cylinders. Consult a reliable vehicle information source for tuning the knock sensor system for the vehicle in question.

The knock sensor is usually screwed directly into the cylinder block and is a piezoelectric sensor. The location of the sensors in a multi-sensor system may vary from manufacturer to manufacturer, but most are located on the sides of the unit (between the water jacket frost plugs). Knock sensors located on the sides of the cylinder block are often screwed directly into the engine coolant passages. When the engine is warm and the engine cooling system is pressurized, removal of these sensors can cause severe burns from hot coolant. Allow the engine to cool before removing any knock sensor and always dispose of coolant properly.

The knock sensor is based on a piezoelectric sensitive crystal. When shaken or vibrated, the piezoelectric crystal creates a small voltage. Since the knock sensor control circuit is usually a single-wire ground circuit, the voltage generated by the vibration is recognized by the PCM as engine noise or vibration. The vibration force that the piezoelectric crystal (inside the knock sensor) encounters determines the level of voltage created in the circuit.

If the PCM detects a degree of knock sensor voltage indicative of spark knock; this may slow down the ignition timing and the knock sensor control code cannot be stored. If the PCM detects a knock sensor voltage level that indicates a louder engine noise (such as a connecting rod contacting the inside of the cylinder block), it may cut off fuel and spark to the affected cylinder and a knock sensor code will appear. stored.

The knock sensor always generates a very low voltage when the engine is running. This is because slight vibration is inevitable, no matter how smoothly the engine runs. If the PCM detects an unexpected signal from knock sensor 4, such as battery voltage, battery full ground, or ripple voltage, a P033E code will be stored and the MIL may illuminate.

Relevant knock sensor / circuit DTCs include P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, P0333, and P0334.

Code severity and symptoms

A stored P033E code may indicate a serious internal engine problem. For this reason, it needs to be addressed urgently.

Symptoms of this code may include:

Reduced engine performance
Oscillation on acceleration
Loud engine noises
Reduced fuel efficiency

reasons

Possible reasons for setting this code:

Defective knock sensor
Internal engine malfunction
Ignition misfires / s
Contaminated or substandard fuel
Faulty knock sensor wiring and / or connectors
Bad PCM or PCM programming error

Diagnostic and repair procedures

Diagnosing the P033E code will require a diagnostic scanner, digital volt / ohmmeter, and a reliable source of vehicle information. If the engine sounds like it is knocking or is too noisy, correct the problem before attempting to diagnose any knock sensor codes.

Consult your vehicle information source for technical service bulletins (TSBs) that match the indicated symptoms and codes stored in the vehicle in question. If the problem you are experiencing is common; the correct TSB can help make a successful diagnosis. Follow the diagnostic instructions given in the TSB and you will probably come to the right solution.

I like to start by visually inspecting all the harnesses and connectors associated with the system. I am looking for burnt, corroded or otherwise broken wiring and connectors that could create an open or short circuit. Knock sensors are often located at the bottom of the cylinder block. This makes them vulnerable to damage when replacing heavy parts (such as starters and engine mounts). System connectors, wiring, and fragile knock sensors often break during repairs nearby.

Connect the scanner to the vehicle diagnostic socket and get all stored codes and freeze frame data. Record this information for use in the diagnostic process. Clear the codes and test drive the vehicle to see if any are reset.

If P033E is reset, start the engine and use the scanner to monitor the knock sensor data. If the scanner shows that the voltage of the knock sensor is not within the manufacturer's specifications, use the DVOM to check the real-time data at the knock sensor connector. If the signal at the connector is within specification, suspect a wiring problem between the sensor and the PCM. If the voltage at the knock sensor connector is out of specification, suspect that the knock sensor is defective.

Additional diagnostic notes:

Multiple knock sensor systems are designed differently depending on the vehicle. Be careful to specify the correct knock sensor for the exposed code.
Beware of hot pressurized coolant when removing knock sensors that are screwed into the engine coolant passages.

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