P0187 OBD2 Code Guide
P0187 is a powertrain diagnostic trouble code. Use this hub to understand the plain meaning, the first checks to run, and which vehicle-specific guides may be more useful before replacing parts.
Fuel Temperature Sensor 2 Circuit Low Input
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.
Code verification standard
P0187 is published with SAE J2012 / ISO 15031-6 code structure plus OBD2 P0187 diagnostic context.
First checks
- - Read all stored and pending codes before clearing anything.
- - Save freeze-frame data so you know speed, load and temperature when the code set.
- - Inspect wiring, connectors, fuses, hoses and obvious leaks tied to the named system.
- - Compare live data against realistic values before buying sensors or modules.
- - Clear the code only after repair and complete a drive cycle to confirm it does not return.
P0187 diagnostic path
- 1Perform a thorough visual inspection of Fuel Temperature Sensor 2, its electrical connector, and the associated wiring harness. Look for any signs of physical damage, corrosion, fraying, or loose connections. Ensure the sensor is securely mounted.
- 2Check for Technical Service Bulletins (TSBs) or recalls specific to your vehicle's make and model that might address known issues related to P0187 or the fuel temperature sensor circuit.
- 3Using a digital multimeter, disconnect the sensor and measure its internal resistance. Compare this reading to the manufacturer's specified resistance values at various temperatures (if available). A low input code often points to an open circuit (infinite resistance) or a short (very low resistance).
- 4With the sensor disconnected, test the integrity of the wiring harness leading to the PCM. Check for continuity, shorts to ground, and shorts to power in both the signal and reference voltage wires. Also, verify the 5V reference voltage and a good ground signal are present at the sensor connector from the PCM.
- 5Utilize an OBD2 scan tool to monitor the live data stream for Fuel Temperature Sensor 2. Observe the reported temperature reading. If it displays an implausible fixed low value (e.g., -40°C/-40°F) or shows no change, this confirms a circuit or sensor malfunction. Compare its reading to other available temperature sensors if possible.
Verify before repair
- - Replace the faulty Fuel Temperature Sensor 2.
- - Repair or replace any damaged wiring or corroded connectors within the fuel temperature sensor circuit.
- - Address any short circuits to ground or power that are detected within the sensor's wiring harness.
- - If all other components test good, diagnose and potentially replace the Powertrain Control Module (PCM) as a last resort.
Vehicle-specific pages to check next
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