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Code P1187

Symptoms

• Check Engine Light illuminated

• Poor fuel economy

• Failed emissions test

Common Causes

• Faulty oxygen sensor

• Damaged wiring or connectors

• Blown fuse for the sensor heater circuit

Glossary

Oxygen Sensor: A device that measures the amount of oxygen in the exhaust gases.

Heater Circuit: An electrical circuit that heats the oxygen sensor to ensure it operates efficiently.

Related Codes

• P0138

• P0141

Official description

O2 Sensor Heater Control Circuit (Bank 2 Sensor 2)

Laymans terms

This code means that the car's computer is having trouble controlling the heater for one of the oxygen sensors. It's like when a heater in your house isn't working right, so the room doesn't get warm enough.

Explanation

The P1187 code indicates an issue with the heater control circuit of the oxygen sensor located on bank 2, sensor 2. This sensor helps the car's computer monitor and adjust the fuel mixture for optimal performance.

Technical description

The oxygen sensor heater is responsible for bringing the sensor up to operating temperature quickly to ensure accurate readings. Bank 2 refers to the side of the engine with the second cylinder in a V-type engine. Sensor 2 is the downstream sensor, which monitors the efficiency of the catalytic converter. A malfunction in the heater circuit can lead to delayed sensor operation and inaccurate fuel mixture adjustments.

Diagnosis steps

• Use an OBD-II scanner to confirm the code

• Inspect the wiring and connectors for damage

• Test the oxygen sensor heater circuit for continuity

Repair procedures

• Replace the faulty oxygen sensor

• Repair or replace damaged wiring

• Replace blown fuse

Tools required

• OBD-II scanner

• Multimeter

• Socket set

Estimated repair cost

$150 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Toyota Camry

• Honda Accord

• Ford F-150

Preventive measures

• Regularly inspect and maintain oxygen sensors

• Ensure wiring harnesses are secure and undamaged

• Use high-quality fuel to prevent sensor contamination

Error code type

Sensor Issue

User experience recommendations

• Have the vehicle inspected by a professional if you are unsure

• Avoid driving long distances until the issue is resolved

Warranty information

Check with your vehicle manufacturer for specific warranty coverage related to emissions components.

Historical data

Oxygen sensor heater circuit issues have been common as vehicles rely more on precise emissions control.

Urgency level

Moderate – While the vehicle is still drivable, prolonged use can lead to increased emissions and potential damage to the catalytic converter.

Legal and safety notice

Driving with a faulty oxygen sensor can lead to increased emissions, which may not comply with local environmental regulations.

Testing conditions

• Engine at operating temperature

• Vehicle in closed-loop operation

Component location

The oxygen sensor is located in the exhaust system, downstream of the catalytic converter on bank 2.

FAQs

Q: Can I drive with a P1187 code?
A: While you can drive with this code, it's best to fix it soon to avoid increased emissions and potential damage.

Q: How do I know if my oxygen sensor is bad?
A: Symptoms include poor fuel economy, a rough idle, and an illuminated check engine light.

Last updated: Apr 16, 2026 • Source: internal database
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