What it means
Fuel temperature sensor B signal exceeds maximum. Shorted to voltage, open ground or open sensor. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Fuel temperature sensor B reports the temperature of fuel at its monitored location to the engine control module. The module monitors the sensor's signal circuit and sets P0188 when the input is higher than its permitted range, which can result from a signal short to voltage, an open sensor or ground, or poor connector contact.
Common causes
Most likely first.
- Signal wire shorted to voltage
- Sensor open-circuit
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Hard starting or rough running
- Reduced engine performance
- Fuel economy may worsen
How to diagnose it
- Check freeze-frame data and live fuel temperature B readings; compare them with other available temperature readings and ambient conditions to see whether the value is implausibly high.
- Inspect sensor B's connector and harness for chafing, moisture, corrosion, pushed-back pins, or a damaged ground connection.
- With the fault active, gently move the harness near sensor B and watch the scan-tool reading for a change that points to an intermittent wiring contact.
- Use the wiring diagram to check sensor B's signal, supply, and ground circuits for an unintended voltage, an open, or excessive resistance.
- If the wiring and connections meet the manufacturer's specification, test fuel temperature sensor B and replace it if its output is out of specification.
Common fixes
- Repair chafed wiring or a signal wire shorted to voltage.
- Clean or repair corroded, loose, or pushed-back connector pins and restore the sensor ground.
- Replace fuel temperature sensor B if it fails testing.
Can I keep driving?
If the engine runs normally, a short, cautious trip may be possible, but hard starting, rough running, reduced performance, or worsening fuel economy can make driving unpredictable. Avoid demanding acceleration and address the fault promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.