Fuel tank pressure sensor codes

How its codes differ

• P0451 is a range or performance fault in the sensor itself: its reading does not behave as expected, so leak results may not be trustworthy until it is fixed.
• P0441 and P0440 can involve the sensor because some systems confirm purge flow by watching tank pressure change; a sensor that does not respond can make good flow look wrong.

Codes

• P0451

  Fuel tank pressure sensor reading out of its expected range

  Severity: Monitor

• P0441

  EVAP purge flow incorrect

  Severity: Monitor

• P0440

  EVAP system fault (general)

  Severity: Monitor

Signs it's failing

• Check engine light with P0451 or EVAP flow codes
• EVAP codes that return after other repairs
• Usually no change in how the car drives

How to test it

1. Fix P0451 or other sensor codes before chasing EVAP leak or flow codes. (Low risk)

2. Comparing the sensor reading with the gas cap off and on, and testing its circuit, needs a scan tool and service information; a shop can do this. (Best left to a shop)

   Warning: Fuel and fuel vapour are flammable. Work with the engine off and cool, in a ventilated area, with no smoking, sparks or flames nearby.

After the repair

• Allow several days of normal driving for the EVAP monitor to run again; it needs particular fuel level and temperature conditions, so it is often the last monitor to complete.
• Clear codes only after the repair, then drive normally over several days with both city and highway driving so the readiness monitors can complete; clearing codes or disconnecting the battery resets them to not ready, which fails an emissions test.