Guide To P0042 OBD Error Code Solutions

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Improper fuel-air ratios can lead to loss of engine power, loss of acceleration and stalling as well as rough idle problems along with check engine light illuminating. This can be due to P0042 error indicating problem with H02s heater control circuit.

P0042 is telling us the ECM has detected a fault in the heated oxygen sensor control circuit for bank 1 sensor 3.

Heated oxygen sensors are usually present in the fuel injection vehicles both before and after the catalytic converters to check on the oxygen levels in the air for proper maintenance of fuel to air ratios.

Fuel injected vehicles use heated oxygen sensors in the exhaust system before and after the catalytic converters to determine oxygen content. This feedback is used to adjust the fuel system accordingly to maintain a proper air/fuel ratio of 14.7:1.

The oxygen sensor uses heater circuit for faster feedbacks to the ECM/PCM. It usually has four wirings out of which two send data to the PCM and two and connected to the heater of the circuit, with all the four wires grounded separately. The P0042 code refers to the third sensor downstream from the engine on bank 1, which is on the side of the engine with the #1 cylinder.

What causes problem of HO2S Heater Control Circuit (Bank 1 Sensor 3)?

• Failure of Bank 1 Sensor 3
• Sensor wiring open/short/damaged
• Open circuit inside Oxygen Sensor or open/ground wires to Bank 1 Sensor 3
• Corroded or Broken Exhaust System ground strap
• Rare ECU (Engine Control Unit) failure
• PCM/ECM or Oxygen Sensor Heater Circuit wiring failed

1. Heated Oxygen Sensor - A faulty sensor will not be able to perform properly and not analyse the air to fuel ratio in the exhaust. Replace damaged oxygen sensors now!
2. Heated Oxygen Sensor Harness - OBD Error Code P0042 may also occur if the sensor harness is damaged as it won’t be able to transmit correct data. Shop for quality oxygen sensor replacement parts now!
3. Heated Oxygen Sensor Connector - A faulty Oxygen Sensor Connector can also lead to improper engine functions. Replace your old connectors now.
4. Heater Circuit Fuse - Damaged Heater Circuit Fuse affects the fuel delivery as well as the exhaust systems. Visit us for quality fuses and parts.
5. Engine Control Module - OBD Error Code P0042 can also be due to faulty EVMs. It’s better to get the faulty electricals replaced as soon as possible. Replace faulty ECM today!
6. Powertrain Control Module - P0042 error code also relates to problems with the powertrain which can store and flash wrong error code. Find all the Powertrain related parts with us.
7. Catalytic Converter - Excessive amounts of unburned gas caused by a misfiring spark plug or a leaky exhaust valve can cause overheating of catalytic converter. Replace your old catalytic converter now!
8. Diagnostic Tool - In order to detect the error, one needs high grade diagnostic tools. Visit us today to grab amazing deals.
9. Exhaust System - Replace faulty exhaust systems and parts as they can be a major reason for flashing of this error in the PCM.

The ECU tries to control the heater circuit and when it detects the issue with the control circuit, it may flash the Check Engine Light on the dashboard.

Following are the ways to correct the OBD Code P0042 error problem.

• Replacement of Bank 1 Sensor 3
• Repair/Replace damaged/short/open wiring
• Changing Bank 1 Sensor 3 fuse
• Replacement of ECU

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• Take the help of a qualified technician to use a scan tool and confirm whether P0042 is present.
• Find and freeze frame data with the code. Then, clear the code.
• Take the vehicle on a test drive under the same conditions.
• If the code reappears, perform a visual inspection of the bank 1 sensor 3 and its wiring.
• If the wiring is okay, the sensor itself will be tested to confirm operation.
• If the HO2S is functioning properly, the technician must check the Engine Control Unit for any faults and damages.

Common mistakes when diagnosing the P0042 code

Always take professional help and follow the diagnosis instructions properly before coming to a conclusion or simply replacing the sensor first.

• Replacing PCM, without checking other components for faults
• Replacing Heated Oxygen Sensor directly
• Not inspecting faulty wiring and connections