P0042

Symptoms

• Check Engine Light Is On
• Increased fuel consumption
• Unstable engine operation at idle
• Reduced engine power
• Increased toxicity of exhaust gases
• Difficulty starting the engine when cold

Causes

• Break or short circuit in the heater wiring
• Faulty oxygen sensor heating element
• Oxidation or corrosion of sensor connectors
• Sensor heater relay malfunction
• Damage to the heater circuit fuse
• Engine control unit malfunction
• Poor contact in the sensor connector

How to Fix

1. Read error codes with a scanner and write down the freeze frame parameters
2. Visually inspect the oxygen sensor and its wiring for damage.
3. Check the integrity of the heater circuit fuses
4. Measure the resistance of the sensor heating element (should be 2-14 Ohms)
5. Check the supply voltage at the sensor connector (should be 12V)
6. Check the integrity of the wiring from the ECU to the sensor
7. Clean oxidized sensor connector contacts
8. If necessary, replace the oxygen sensor
9. Clear error codes and take a test drive
10. Recheck for errors

Related codes

Error P0042 by Vehicle Brand