P0188 OBD2 Code Guide
P0188 is a powertrain diagnostic trouble code. Use this hub to understand the plain meaning, the first checks to run, and which vehicle-specific guides may be more useful before replacing parts.
Fuel Temperature Sensor 2 Circuit High Input
Code P0188 signifies that the Powertrain Control Module (PCM) has detected an abnormally high voltage signal from Fuel Temperature Sensor 2. This 'high input' typically indicates an open circuit, a short to voltage, or a faulty sensor reporting an implausibly low fuel temperature (as resistance decreases with increasing temperature, a high voltage often means an open circuit or very high resistance, which the PCM interprets as very cold fuel). This sensor is crucial for the PCM to accurately calculate fuel density and adjust fuel injection timing and quantity for optimal combustion efficiency, emissions control, and engine performance. A high input can lead to incorrect fuel mixture adjustments, potentially causing poor fuel economy, rough idling, hesitation, or increased emissions.
Code verification standard
P0188 is published with SAE J2012 / ISO 15031-6 code structure plus OBD2 P0188 diagnostic context.
First checks
- - Read all stored and pending codes before clearing anything.
- - Save freeze-frame data so you know speed, load and temperature when the code set.
- - Inspect wiring, connectors, fuses, hoses and obvious leaks tied to the named system.
- - Compare live data against realistic values before buying sensors or modules.
- - Clear the code only after repair and complete a drive cycle to confirm it does not return.
P0188 diagnostic path
- 1Connect an OBD-II scanner to confirm P0188 and check for any other related codes. Visually inspect Fuel Temperature Sensor 2 and its wiring harness for any obvious damage, corrosion, loose connections, or signs of rodent damage. Pay close attention to the connector pins.
- 2Disconnect the sensor connector. Using a multimeter, check for the 5-volt reference signal and a good ground at the sensor's harness connector. If either is missing, trace the wiring back to the PCM for opens or shorts. If present, proceed to test the sensor itself.
- 3With the sensor disconnected, measure its resistance across its terminals using a multimeter. Compare this reading to the manufacturer's specifications for the ambient fuel temperature. A "high input" code often correlates with an open circuit (infinite resistance) or extremely high resistance in the sensor, indicating a fault within the sensor itself.
- 4If the sensor tests good, reconnect it and check the continuity of the signal wire from the sensor connector back to the PCM connector. Also, check for any short to voltage or ground in the signal wire. A short to voltage would explain the "high input."
Verify before repair
- - Replace the faulty Fuel Temperature Sensor 2.
- - Repair or replace damaged, corroded, or open wiring and connectors in the sensor's circuit.
- - Address a short to voltage in the fuel temperature sensor 2 signal wire.
- - In rare cases, replace the Powertrain Control Module (PCM) if all other components and wiring test good.
Vehicle-specific pages to check next
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