What it means
The control circuit for the heater in the Bank 1 Sensor 2 heated oxygen sensor has a malfunction.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 2 is the heated oxygen sensor after the catalytic converter on the bank that contains cylinder 1. Its heater warms the sensor so the control module can use its signal sooner. P0042 sets when the module detects a malfunction in the heater control circuit, without specifying a low or high circuit reading.
Common causes
Most likely first.
- Heater element open
- Heater wiring or connector fault
Symptoms
- Check-engine light on
- Oxygen-sensor heater may warm slowly
- Fuel economy may decrease
- Emissions may increase
How to diagnose it
- Read the freeze-frame data and any related heater or oxygen-sensor codes to see when the Bank 1 Sensor 2 heater fault occurred.
- With the exhaust cool, inspect the Bank 1 Sensor 2 connector and nearby wiring for disconnection, heat damage, corrosion, or a pushed-back pin.
- Check the heater fuse and power supply for the Bank 1 Sensor 2 circuit using the vehicle wiring diagram.
- Test the sensor heater element and its wiring for continuity or an open circuit, following the manufacturer's procedure.
- If the sensor and wiring test correctly, check the control side of the heater circuit and module command using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect or clean the Bank 1 Sensor 2 heater connector if it is loose or contaminated.
- Repair damaged or open wiring in the Bank 1 Sensor 2 heater circuit.
- Replace the Bank 1 Sensor 2 oxygen sensor if its heater element is open or otherwise fails the specified test.
- Repair the heater power supply or control fault if testing identifies it outside the sensor.
Can I keep driving?
You can usually drive gently if the engine runs normally, but arrange diagnosis soon because the downstream sensor may take longer to become usable and emissions can increase. Stop driving if the engine develops severe running problems or an exhaust warning is accompanied by other serious symptoms.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.