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P0445Evaporative Emission Control System Purge Control Valve Circuit Shorted

The engine computer detects a short circuit in the EVAP purge control valve's wiring or solenoid, drawing incorrect current.

Definition

The PCM monitors current and voltage on the purge valve driver circuit every time the solenoid is commanded. P0445 sets when the circuit is shorted — either the control wire is shorted to ground or voltage, or the solenoid winding itself has shorted internally, causing excessive current draw. Driveability is usually unaffected, but the MIL turns on and, if the short holds the valve energized, unmetered vapor purge at idle can cause rough running or hard hot starts; a hard short can also damage the PCM driver over time.

Common causes

  • Internally shorted purge solenoid winding (low coil resistance)
  • Control wire chafed through and shorted to chassis ground
  • Control wire shorted to a voltage source in a damaged harness section
  • Connector contaminated with fuel, oil, or water bridging terminals
  • Melted harness section routed too close to exhaust components
  • Damaged PCM driver transistor (often a result, not a cause)

Common misdiagnoses

  • Gas cap replaced for an electrical short-circuit fault
  • Charcoal canister replaced when the solenoid coil is shorted
  • PCM replaced without finding the harness short that damaged it
  • Idle or fuel-trim complaints chased with sensors when a stuck-energized purge valve is the cause

Troubleshooting steps

  1. 1.Measure the purge solenoid coil resistance

    Compare to spec (typically 20-40 ohms); a reading of just a few ohms indicates a shorted winding and a failed solenoid.

  2. 2.Check the control wire for a short to ground

    With the valve and PCM connectors disconnected, resistance from the control wire to chassis ground should be infinite (OL).

  3. 3.Check the control wire for a short to voltage

    With key on and the valve unplugged, the control wire should not show battery voltage on the PCM side when the driver is commanded off.

  4. 4.Inspect harness routing

    Look for melted insulation near the exhaust manifold or EGR tube and chafe points at brackets where the purge valve harness passes.

  5. 5.Verify the valve is not stuck energized

    At idle, disconnect the purge valve; if idle quality changes noticeably, the valve was flowing when it should have been closed.

  6. 6.Repair, clear codes, and retest

    Cycle purge with a scan tool through several drive cycles and confirm no reoccurrence and normal fuel trims.

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