Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer has detected a problem with the heater in one of the oxygen sensors. It's like a tiny heater that helps the sensor work better, and it's getting too much electricity.
The O2 sensor heater circuit is responsible for heating the oxygen sensor to ensure it operates efficiently. A high voltage condition indicates an electrical issue where the voltage is higher than expected.
The P1139 code is triggered when the Engine Control Module (ECM) detects a higher than normal voltage in the heater circuit of the downstream oxygen sensor (Bank 1 Sensor 2). This can be due to wiring issues, a faulty sensor, or a malfunctioning ECM.
• Check Engine Light illuminated
• Poor fuel economy
• Failed emissions test
• Faulty oxygen sensor
• Damaged wiring or connectors
• Malfunctioning ECM
ECM: Engine Control Module
O2 Sensor: Oxygen Sensor
• Use an OBD-II scanner to confirm the code
• Inspect the wiring and connectors for damage
• Test the oxygen sensor's heater circuit
• Replace the faulty oxygen sensor
• Repair or replace damaged wiring/connectors
• Reprogram or replace the ECM if necessary
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Honda Accord
• Toyota Camry
• Ford Focus
• Regularly inspect and maintain the exhaust system
• Ensure proper electrical connections
• Use high-quality fuel
Sensor Issue
• Address the issue promptly to avoid further damage
• Consult a professional mechanic if unsure
• Regular maintenance can prevent such issues
Check your vehicle's warranty for coverage on emissions-related components.
This code has been associated with vehicles that have aging oxygen sensors or electrical issues.
Moderate – While the car may still run, it could lead to poor fuel efficiency and emissions issues.
Ignoring this code may lead to failing emissions tests and potential fines in areas with strict emissions regulations.
• Engine at operating temperature
• Vehicle at idle or under load
The oxygen sensor is located in the exhaust system, downstream of the catalytic converter on Bank 1.
Q: Can I drive with a P1139 code?
A: While you can drive with this code, it's not recommended as it may lead to poor fuel efficiency and emissions problems.
Q: How do I know if my oxygen sensor is bad?
A: Symptoms include poor fuel economy, rough idling, and the Check Engine Light being on.
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Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when the code or supporting diagnostics point toward upstream or downstream oxygen-sensor faults.
This code family often involves upstream or downstream oxygen-sensor diagnosis.
Verify exact sensor position and vehicle fitment before buying.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.