Based on the provided codes, P1157 and P1158 refer to faults in the oxygen sensor and Air/Fuel (A/F) sensor circuits, not an engine compartment temperature sensor
. The exact meaning depends on the make and model of the vehicle. The references to "Engine compartment temperature sensor" in your query likely caused a misinterpretation, as these P11XX codes are manufacturer-specific. Here is what these codes typically mean for specific car makes:
P1157 code
- For Honda: This code indicates an issue with the Air/Fuel Ratio (A/F) Sensor 1, which is the upstream or primary oxygen sensor located in the exhaust manifold. The specific fault is a "High Voltage" reading from the sensor.
- For Ford: This code, sometimes seen with P1158, can refer to a lack of switching from the HO2S22 sensor.
- Possible causes for Honda (P1157):
- A faulty A/F sensor.
- Damaged or corroded wiring or connectors.
- Exhaust manifold leaks that cause incorrect sensor readings.
- A problem with the sensor heater circuit.
P1158 code
- For Ford: This code, often seen with P1157, can indicate a lack of HO2S22 switch—the sensor on bank 2 is stuck on a rich reading.
- For BMW: This code can point to a fuel trim issue, specifically "Fuel Trim Additive Bank 1 Low".
- Possible causes for Ford (P1158):
- Faulty oxygen sensor (the HO2S22 sensor).
- A rich running condition in the engine.
- Faulty sensor wiring or circuit.
Common diagnostic steps
Because the codes are manufacturer-specific, a proper diagnosis requires using a specialized scan tool and the factory service manual for your vehicle.
- Verify the code with a scan tool: Use an OBD-II scanner to confirm the specific P1157 or P1158 code and read any accompanying codes.
- Inspect the sensor and wiring: Visually inspect the oxygen or A/F sensor and its wiring harness for any signs of damage, corrosion, or frayed wires.
- Check for exhaust leaks: An exhaust leak near the oxygen sensor can cause incorrect readings. Check for any leaks in the exhaust manifold.
- Test the sensor: Use a multimeter or a diagnostic tool to test the voltage and resistance of the sensor and its heater circuit.
- Monitor live data: With an advanced scan tool, monitor the sensor's live data to see if it is switching correctly (for an oxygen sensor) or maintaining the proper voltage (for an A/F sensor).
Important note
The information on JustAnswer highlights the importance of using high-quality Original Equipment Manufacturer (OEM) sensors for replacement, as cheaper aftermarket sensors can sometimes cause the code to return.
