P0188 Fuel Temperature Sensor B Circuit High

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. P0188 means the signal of sensor B is above its valid range – typically an open circuit or unplugged connector, so the module would read about −40 to −50 °C. GM's 6.6 litre diesel sets it above 4.75 V (below about −50 °C) for 5 s; on GM's direct-injection petrol engines the digital rail temperature sensor 2 sets it above a count of 1865, after two trips.

Likely causes

Symptoms

• Check engine light on
• Fuel temperature about −40/−50 °C in scan data
• Usually no change in driving

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.