P0187: Fuel temperature sensor B reports a voltage below the normal limit
Fuel temperature sensor B circuit low input
Severity: Monitor
TroubleCodes.net lists poor fuel economy, hard starting and poor performance for P0187, none of which is an immediate danger, so keep driving gently and book a check.
P0187 in short
P0187 means the engine computer saw the fuel temperature sensor B signal drop below its calibrated limit, which reads as an unusually hot fuel temperature. A short or open in the wiring, water or corrosion, or a faulty sensor are the usual causes. You may notice hard starting or poorer economy.
The fuel temperature sensor tells the computer how warm the fuel is so it can adjust fuel delivery. A low voltage from the sensor reads as a high temperature.
When that voltage is lower than the calibrated limit the computer stores P0187. TroubleCodes.net traces it to wiring faults first, then the sensor, with the computer last.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Short or open circuit, corrosion or water in the wiring
Common general cause- Why it ranks here
- TroubleCodes.net lists wiring shorts, opens, water entry and harness damage first.
- What would change this
- Rises if flexing the harness changes the reading or resistance is high. Falls if circuit checks pass.
Cause 2: Faulty fuel temperature sensor
Common general cause- Why it ranks here
- TroubleCodes.net says to measure sensor resistance against the manual and replace it if out of range.
- What would change this
- Rises if resistance is out of specification. Falls if it is within range.
Cause 3: Engine control module fault
Possible — needs testing- Why it ranks here
- TroubleCodes.net calls this less common.
- What would change this
- Rises only after wiring and sensor test good.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Check the sensor connector for bent pins or corrosion and confirm 5 volts reference from the computer.
Warning:Keep the ignition off when unplugging connectors and avoid shorting the 5-volt reference to ground, which can damage the computer.
IfPins are damaged or reference voltage is missing
It meansA wiring fault is likely.
Points to: Short or open circuit, corrosion or water in the wiring
IfConnector and reference are good
It meansMeasure the sensor resistance.
Step 2: Measure the sensor resistance and compare with the repair manual, flexing the harness to catch intermittent faults.
IfResistance is out of range
It meansThe sensor is suspect.
IfResistance is correct
It meansTest the wiring back to the computer.
Points to: Short or open circuit, corrosion or water in the wiring
Symptoms
- Check engine light on
- Poor fuel economy
- Hard starting
- Poor engine performance
How to fix
Step 1: With the engine off, look over the sensor connector and nearby wiring for damage or corrosion.
On your vehicle
We don't have reviewed vehicle-specific evidence for P0187 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0187 yet.
Sources and review
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
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