P0051 Fault Code

P0051 OBD-II Trouble Code Short Description

HO2S Heater Control Circuit Low (Bank 2 Sensor 1)

What does trouble code P0051 mean?

The P0051 fault code on cars refers to a problem with the HO2S (Heated Oxygen Sensor) heater control circuit on Bank 2 Sensor 1. This sensor is responsible for monitoring the oxygen levels in the exhaust gases and providing feedback to the engine control module (ECM) for proper fuel and air mixture control.

When the ECM detects a low voltage or resistance in the heater control circuit of the Bank 2 Sensor 1 oxygen sensor, it will trigger the P0051 fault code. This low voltage or resistance can be caused by a few different issues, such as a faulty oxygen sensor, a damaged oxygen sensor heater circuit, or a problem with the wiring or connections associated with the oxygen sensor.

To diagnose and repair this issue, the following steps can be taken:

  1. Check the wiring and connections: Inspect the wiring and connections related to the Bank 2 Sensor 1 oxygen sensor. Look for any signs of damage, corrosion, or loose connections. Repair or replace any faulty wiring or connectors as necessary.

  2. Test the oxygen sensor: Use a scan tool or multimeter to test the voltage and resistance of the Bank 2 Sensor 1 oxygen sensor. Compare the readings to the manufacturer's specifications. If the oxygen sensor is not functioning within the specified range, it may need to be replaced.

  3. Check the oxygen sensor heater circuit: Test the heater circuit of the Bank 2 Sensor 1 oxygen sensor to ensure it is receiving the proper voltage. If the voltage is too low, there may be a problem with the ECM, a blown fuse, or a faulty relay. If the voltage is correct and the oxygen sensor is still not heating up, the sensor may need to be replaced.

  4. Clear the fault code: After repairs have been made, use a scan tool to clear the fault code from the ECM's memory. This will turn off the Check Engine Light and allow for monitoring of the oxygen sensor's performance.

It is important to address the P0051 fault code promptly, as it can negatively impact fuel efficiency and emissions. Ignoring this issue may lead to further damage to the oxygen sensor or other components of the engine management system.


What are the symptoms of the P0051 code?

The P0051 fault code relates to the HO2S (Heated Oxygen Sensor) Heater Control Circuit being low in Bank 2 Sensor 1. Here are some common symptoms associated with this fault code:

  • Check Engine Light (CEL) is illuminated
  • Poor engine performance
  • Decreased fuel efficiency
  • Rough idling or stalling
  • Difficulty starting the engine
  • Increased emissions

It is important to note that these symptoms may vary depending on the make and model of your vehicle. If you have observed any of these symptoms, it is recommended to have your vehicle diagnosed and repaired by a qualified technician.


What causes the P0051 code?

P0051 - HO2S Heater Control Circuit Low (Bank 2 Sensor 1)

The P0051 fault code indicates a problem with the HO2S (Heated Oxygen Sensor) heater control circuit on bank 2 sensor 1 of the vehicle's engine. Here are some possible causes for this fault code:

  1. Faulty oxygen sensor: The oxygen sensor itself may be defective and not functioning properly. This can cause the heater control circuit to operate at a low voltage, triggering the P0051 code.

  2. Wiring issues: Damaged or faulty wiring can cause a low voltage condition in the heater control circuit, resulting in the P0051 fault code.

  3. Faulty heater control circuit relay: A faulty relay in the heater control circuit can cause the voltage to drop, triggering the P0051 code.

  4. ECU (Engine Control Unit) issue: A malfunctioning or faulty ECU may prevent the proper voltage supply to the heater control circuit, leading to the P0051 fault code.

  5. Exhaust leak: An exhaust leak in the vicinity of the oxygen sensor can cause the heating element to malfunction, resulting in the P0051 code.

It is recommended to have a professional mechanic diagnose and repair the issue as they will have the necessary tools and knowledge to accurately identify the cause of the fault code and carry out the appropriate repairs.

Possible Solutions

How to fix P0051?

To fix the P0051 fault code on cars, you can follow these steps:

  1. Check the wiring: Inspect the wiring harness and connector for any damage or loose connections. Repair or replace any damaged parts as necessary.

  2. Check the oxygen sensor: Remove the oxygen sensor from Bank 2 Sensor 1 and inspect it for any signs of damage or contamination. Clean or replace the sensor if needed.

  3. Test the heater circuit: Use a multimeter to test the heater circuit of the oxygen sensor. Check for continuity and proper resistance. If the readings are out of specification, replace the oxygen sensor.

  4. Check the PCM: If all the previous steps check out, the problem may lie in the Powertrain Control Module (PCM). Have the PCM checked and reprogrammed or replaced if necessary.

  5. Clear the fault code: Once the issue has been addressed, clear the fault code using an OBD-II scanner or code reader. This will reset the Check Engine Light and allow you to monitor for any recurring issues.

It is recommended to consult a professional mechanic or refer to the specific repair manual for your car's make and model for more detailed instructions.