P0185 Fuel Temperature Sensor B Circuit — Causes & Fix

What Does P0185 Mean?

P0185 flags an implausible fuel temperature signal. The ECU uses fuel temperature to correct injection quantity (diesel expands as it warms), so a bad reading causes poor hot starting, uneven running and inaccurate fuelling. Wiring and connector checks come before the sensor — and genuinely hot fuel from excessive injector back-leak must be ruled out.

P0185 at a Glance

• What it means: The fuel temperature sensor signal is outside its plausible range.
• Most common cause: Fuel temperature sensor failure
• Severity: Moderate to serious — rail-pressure faults cause power loss and non-starts.
• Can you drive?: Short distances in limp mode only. Diagnose promptly.
• Typical repair cost: £40-£150 for sensor/regulator work; £100-£350 per injector where back-leak is the cause.