P1172 - FAULT CODE - OBD2

P1172 ACURA, HONDA: REAR A/F SENSOR BANK 1 SENSOR 1 CIRCUIT OUT OF RANGE HIGH

The A/F Sensor 1 (Air/Fuel Ratio Sensor) is installed in the vehicle’s exhaust and its purpose is to measure the oxygen content in the exhaust. This sensor sends an output signal to the ECM (Engine Control Module), which will make the respective adjustments to the fuel mixture accordingly. A heater integrated into the Air/Fuel Ratio Sensor is activated, which causes the sensor to increase its temperature until it can accelerate oxygen detection by controlling the current flowing through the heater. The current increase is deactivated when the voltage applied to the heater reaches a certain range, where the oxygen carried to the diffusion layer is limited.

The air/fuel ratio is detected by the current amperage, taking into account that the amperage is proportional to the oxygen in the exhaust. The ECM compares the actual ratio with the expected ratio, and thus controls the fuel injection timing.

When voltages considered out of range for being excessively high are detected in the A/F Sensor 1 circuit for the engine bench, the fault code P1172 OBD2 will be set.

• Check Engine lamp illuminated.
• The engine has unstable performance.
• Problems during idling.

P1172 OBDII diagnostic code is stored for the following:

• The Air/Fuel Ratio Sensor may have damage to the wires or connectors.
• The A/F sensor 1 may have been damaged.
• A fuel injector may be in poor condition.
• Fuel pressure may not be sufficient.

It is recommended that if you do not know mechanics, go urgently to the nearest garage in your city and have a professional fix and correct this code on your car. If, on the other hand, you have the necessary knowledge to solve this fault, you can use some tools such as an OBD2 meter that will help you to remove this message or alert from the dashboard of your vehicle. Read on and buy the model that best suits your car's requirements. These are some of the steps to follow to correct the DTC P1172 OBD2 code:

• Consult the TSBs.
• Inspect all electrical components of the Air/Fuel Ratio Sensor and check that they are all in good condition. Repair damage caused by corrosion, wear, or burns.
• Verify that the fuel pressure is at the proper levels. Insufficient pressure may be due to a bad injector. Make the respective corrections.
• Using the appropriate tools, check if the resistance of the A/F Sensor is as indicated in the service manual. An out-of-range resistance requires replacing the sensor.