P0187 Fuel Temperature Sensor B Circuit Low

Fuel temperature sensor B is an NTC thermistor: the hotter the fuel, the lower its resistance and signal voltage. On diesels it sits in the injection pump, rail or return line; on Ford petrol direct-injection engines it is built into the rail pressure sensor, and GM uses digital rail temperature sensors on its direct-injection engines. Sensor B is the second measuring point, for example GM's 6.6 litre diesel sensor 2 or a second rail. P0187 means the signal of sensor B is below its valid range – with an analogue NTC a short to ground or very hot reading. GM's 6.6 litre diesel sets it below 0.60 V (above about 150 °C) for 5 s; GM's direct-injection petrol engines use a digital rail temperature sensor 2 and set it below a count of 145 in 50 of 62 samples, two trips – communication faults of these digital sensors have codes of their own.

Likely causes

Symptoms

• Check engine light on
• Implausibly high fuel temperature in scan data
• Possibly starting problems

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com.