P0188
Fuel Temperature Sensor B Circuit Low Input
Powertrain Fuel and Air Metering Fuel Temperature Sensing 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

Your fuel temperature sensor is sending a signal that's too low, like a thermometer stuck on cold when it's actually warm. The engine computer can't accurately read how hot the fuel is, which affects fuel injection timing and efficiency.

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Symptoms You May Notice
3 known symptoms for this code
Check Engine Light illuminated
Poor fuel economy
Rough idle or hesitation during acceleration
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the fuel temperature sensor voltage to adjust fuel density calculations and injection strategies. A low voltage reading (below ~0.5V) indicates the sensor circuit resistance is too high or the signal wire is shorted to ground. The ECM expects a specific voltage range that corresponds to fuel temperature between -40°C and 125°C.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Sensor Voltage 0.5V - 4.5V Below 0.5V (Low Input)
Fuel Temperature Range -40°C to 125°C Reading below -40°C equivalent
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Electrical connectors and harness
Inspect the fuel temperature sensor connector for corrosion, loose pins, or moisture and clean or reseat as needed.
2
Wiring harness
Check the sensor signal wire for damage, pinches, or shorts to ground along the fuel line routing.
3
Fuel Temperature Sensor
Replace the sensor if connector and wiring are clean and secure, as internal sensor failure causes constant low voltage.