Honda Civic P0187: Fuel Temperature Sensor 2 Circuit Low Input diagnosis
Code verification standard
P0187 is published with SAE J2012 / ISO 15031-6 code structure plus Honda Civic diagnostic context.
This page covers meaning, symptoms, first checks, live data, misdiagnosis risk, and repair verification.
What does this mean?
Code P0187 signifies that the Powertrain Control Module (PCM) has detected a low voltage input from Fuel Temperature Sensor 2. This sensor is crucial for monitoring the temperature of the fuel, which directly impacts its density and viscosity. The PCM uses this data to precisely adjust fuel injection timing and duration, ensuring optimal air/fuel mixture, efficient combustion, and reduced emissions. A low input typically indicates an open circuit, a short to ground, a faulty sensor, or a problem within the PCM itself, leading to incorrect fuel calculations and potential drivability issues such as poor fuel economy or rough idling.
How serious is this code?
While P0187 may not immediately render the vehicle undrivable, it can lead to significant drivability issues such as rough idling, poor fuel economy, reduced engine performance, and increased emissions. Incorrect fuel temperature readings can cause the PCM to miscalculate fuel delivery, potentially leading to an overly rich or lean condition. Prolonged driving with this issue can damage catalytic converters, spark plugs, or other critical engine components due to improper combustion. It is advisable to diagnose and repair this code promptly to prevent further damage and ensure optimal vehicle operation.
Diagnostic system: General powertrain circuit
On a Honda Civic, the P0187 code should be diagnosed as part of the general powertrain circuit group. Related codes and live data from this same system can change the repair priority, so avoid replacing parts from the code name alone.
Most Common Causes for Honda Civic
- Faulty fuel temperature sensor
- Damaged, chafed, or broken wiring harness
- Corroded or loose electrical connector
- Vacuum leak in intake system
- PCM/ECM software needs update (TSB)
- Internal PCM/ECM failure
Symptoms to Watch For
- Check Engine Light is illuminated
- Difficulty starting the engine
- Decreased fuel economy
- Rough or unstable idle
- Significant loss of engine power
- Poor acceleration or sluggish response
- Hesitation or stumble during acceleration
Before replacing parts, check these first
- Record freeze-frame data and related codes before clearing the fault.
- Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system.
- Use live data or a multimeter to confirm the failed circuit before replacing parts.
- Check for blown fuses, weak battery voltage, and damaged connectors before buying major parts.
Live data to compare
- Freeze-frame conditions
- Related codes
- Circuit voltage and continuity
How to Diagnose
Common Mistakes
Treating the code description as a parts list instead of verifying the circuit, operating conditions, and related codes. Always confirm the fault with freeze-frame data, live data, visual inspection, and circuit checks before spending money on parts.
Repair verification
After the repair, clear P0187, complete a drive cycle, and confirm the monitor runs without the code returning. Save the before/after scan report if the vehicle needs emissions inspection.
Frequently Asked Questions
Can I drive with the P0187 code?
If the check engine light is solid, you can usually drive to a safe location or mechanic. If the light is flashing, pull over immediately to prevent catastrophic engine or catalytic converter damage.
Will the P0187 code clear itself?
Once the underlying problem is fixed, the engine computer will run its self-checks. If it passes over several drive cycles, the light will turn off automatically. You can also clear it immediately using an OBD2 scanner.
Will this code fail an emissions test?
Yes. If the Check Engine Light is on due to the P0187 code, your Honda will automatically fail an OBD2 plug-in emissions or smog test.
What should I check first for P0187?
Record freeze-frame data and related codes before clearing the fault. Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system. Use live data or a multimeter to confirm the failed circuit before replacing parts.
Join the Discussion
Repair Estimate
Fuse, connector, wiring, cleaning, or basic inspection
Major component replacement after live data and circuit tests confirm failure
Costs vary widely; start with visual inspection and circuit confirmation to avoid unnecessary parts.
DIY Difficulty
Can usually be performed at home with basic hand tools.