P0188 is set when the Powertrain Control Module (PCM) sees a voltage that is higher than the expected range for the Fuel Temperature Sensor B circuit. This usually means the sensor signal is stuck at a high voltage, which can be caused by an electrical fault rather than an actual excessively hot fuel condition. The code is a diagnostic indicator that something in the sensor’s wiring or the sensor itself is not operating correctly.
The sensor’s internal circuitry can short or open, causing the signal voltage to stay high even when the fuel is not hot.
A damaged wire, broken insulation, or corroded terminal can short the sensor signal to battery voltage or create an open circuit.
A wiring harness that contacts a switched‑on power source can pull the sensor voltage up, triggering the code.
An inadequate ground path can force the signal voltage high, similar to a short condition.
The control module itself can output an incorrect reference voltage or misread the sensor, but this is far less common than the above causes.
The vehicle can usually be driven short distances, but the underlying fault may cause poor fuel economy or drive‑ability issues, so it’s best to diagnose and repair it promptly.
No. While a faulty PCM can cause this code, it is rarely the culprit; most cases are resolved by repairing the sensor or wiring.
Yes, an inaccurate fuel‑temperature reading can affect the fuel‑mixture strategy, potentially triggering fuel‑trim or O2‑sensor codes.
It is a moderate‑priority issue. Ignoring it may lead to decreased fuel efficiency and possible drive‑ability symptoms, but it is not a safety‑critical failure.