P0451 — Rationality of the tank pressure sensor fuel

Causes

• Faulty tank pressure (EVAP) sensor
• Wiring issues: open, short to ground, short to voltage, poor connector
• Corroded or damaged sensor connector terminals
• Leaking or collapsed EVAP hoses or fittings affecting sensor reading
• Blocked or restricted EVAP lines or vent path
• Faulty fuel tank pressure sensor reference or supply voltage

Symptoms

• MIL/Check Engine lamp illuminated
• Possible failed EVAP system readiness during emissions test
• Fuel smell or evidence of fuel vapor leakage in vehicle bay (sometimes)
• Occasional rough running not typically caused by this code alone
• Difficult to clear code until fault is repaired

What to check

• Read all stored DTCs and freeze frame / live data for EVAP pressure
• Visual inspection of sensor, connector, and EVAP lines for damage or disconnection
• Check for corrosion, bent pins or moisture in the sensor connector
• Backprobe sensor signal, ground and 5V (reference) with ignition on and compare to expected
• Wiggle harness and connector while monitoring live data for intermittent faults
• Perform smoke test of EVAP system to identify leaks and verify vent path

Signal parameters

• Reference voltage: typically around 5 V (check vehicle specification)
• Signal voltage at atmospheric pressure: approximately mid-scale (about 2–2.5 V typical)
• Expected sensor range: sensor should change smoothly across its stated range (e.g., ~0.5–4.5 V) as system pressure/vacuum changes
• No signal: near 0 V or stuck at a constant value indicates open/short or failed sensor
• Rapid or erratic jumps in signal indicate intermittent connection or internal sensor failure

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