Powertrain, generic · Auxiliary emission controls

P0452 EVAP System Pressure Sensor/Switch A Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The evaporative emission (EVAP) system stores fuel vapour from the tank in a charcoal canister; a purge valve lets the engine draw it off, and a vent valve opens the canister to fresh air. The tank pressure sensor measures small pressures around ambient for the leak tests. Its direction differs by maker – on GM vacuum raises the voltage, on Ford and Bosch pressure does – so low and high refer to the signal voltage only. P0452 means its signal voltage is below the lower limit: GM below 0.15 V (640 of 800 samples, MIL after two trips), Ford below 0.1 V for 5 s, Saab below 0.1 V for more than 5 s. Common causes are a signal wire shorted to ground, an interrupted or shorted 5 V reference or a faulty sensor. Leak and purge tests are then suspended.

Likely causes

Signal wire shorted to ground or connector corroded
Tank pressure sensor faulty internally
5 V reference open or shorted (shared reference)
Engine module

Symptoms

  • Check engine light on
  • EVAP readiness not set, emission inspection not passed
  • No change in driving

Repair estimate

DifficultyMediumDIY possible
Parts and labour€40–250
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel tank pressure sensorsensor wiringengine control module

Related codes

P0450P0451P0453P0454P0642P0455

References: gsi.ext.gm.com, newtonnet.co.uk, saabwisonline.com, saabwisonline.com.