P0187
Fuel Temperature Sensor B Circuit Range/Performance
Powertrain Fuel and Air Metering Fuel temperature sensing 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The engine computer detected that the fuel temperature sensor B is reading outside its normal range or not responding correctly. Think of it like a thermometer that's either broken or giving wildly inaccurate temperature readings.

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Symptoms You May Notice
3 known symptoms for this code
Check Engine Light illuminated
Poor fuel economy or rough idle
Difficulty starting in cold weather
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors voltage from fuel temperature sensor B to track fuel temperature for precise fuel injection timing and quantity adjustments. The sensor should produce a voltage signal that varies linearly with temperature changes. If the signal stays constant, drops to zero, or exceeds expected voltage thresholds, the ECU logs a fault.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor Voltage 0.5-4.5V varying with temperature Out of range, stuck value, or erratic fluctuation
Temperature Reading -40°C to 125°C (-40°F to 257°F) Implausible rate of change or static reading
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Fuel temperature sensor B connector
Inspect and clean the connector pins for corrosion or debris that may cause poor electrical contact.
2
Fuel temperature sensor B wiring harness
Check wiring for damage, pinching, or loose connections along the fuel line routing.
3
Fuel temperature sensor B
Replace the sensor if voltage readings remain out of spec after connector and wiring inspection.