P24BE

Code

Generic P — Powertrain

EVAP System Leak Detection Pump Switching Valve Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 33 RU: 15

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Page language: EN

Causes

Open or shorted wiring in the switching valve control circuit
Connector corrosion, bent pins, poor terminal contact, or water intrusion at the valve or PCM connector
Failed EVAP leak detection pump switching valve (stuck or electrically shorted)
Blown fuse, faulty relay, or supply voltage issue to the EVAP subsystem
PCM/ECM driver fault or internal failure (less common)
Aftermarket modifications or damage to EVAP harness (repairs, aftermarket parts)

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Vehicle may fail EVAP leak test or show EVAP readiness incomplete
Possible EVAP system test faults or stored EVAP-related trouble codes
Rarely: faint fuel odor if EVAP test can’t be completed

What to check

Visual inspection of EVAP switching valve, pump, and wiring harness for damage, chafing, corrosion, or water intrusion
Inspect connectors and pins at the switching valve and at the PCM for corrosion, bent pins, or pushed-out terminals
Check related fuses and relays for continuity and correct power supply
Use a scan tool to read freeze frame and live data, and attempt to command the valve ON/OFF while monitoring circuit voltage
Backprobe the valve connector to measure voltage and ground while commanding the valve (engine off, key on)
Measure resistance of the valve coil with connector disconnected and compare to service specification

Signal parameters

When commanded OFF: control circuit should typically be near battery voltage (open/high) — consult vehicle manual for exact value
When commanded ON: low-side drivers usually pull control circuit near 0 V (ground) or a PWM duty; the expected low-level is ~0–1 V when driven (varies by design)
Valve coil resistance: typically measured with connector disconnected; acceptable range commonly falls between about 10–100 ohms depending on design — check OEM spec
Current draw when energized typically ranges from a few hundred milliamps to a couple of amps depending on valve; compare with spec
If ECM uses PWM, expect a pulsed signal: record frequency and duty cycle with a scope and compare to service data

Diagnostic algorithm

Safety: Park, key off, battery stable. Follow shop safety and battery disconnect procedures if required by vehicle manual.
Scan tool: Read and record freeze frame data and stored codes. Note EVAP test status and other related DTCs.
Visual: Inspect switching valve, pump, hoses, and wiring for damage, corrosion, or signs of recent repair.
Fuses/relays: Verify related fuses and relays are present and good. Replace if blown and test.
Connector check: Unplug switching valve connector, inspect pins for corrosion or damage, then reconnect securely.
Command test: Backprobe valve connector with key on engine off. Using a scan tool or jumper, command the valve ON and OFF while monitoring voltage at the control pin and reference/ground pin. Expect battery voltage when OFF and near 0 V (or a PWM) when ON — consult service manual.
Coil resistance: With connector disconnected, measure coil resistance. If open or shorted (outside spec), replace valve.
Wiring continuity: Check continuity from valve connector to PCM connector; check for shorts to ground or battery using an ohmmeter. Repair damaged wiring or connectors.
Load test and current draw: Measure current when valve is commanded on to confirm it’s within spec; excessive current implies short or internal valve fault, zero/no current implies open circuit.
Isolate harness: If the harness shows intermittent faults, wiggle test while commanding to reproduce; repair or replace wiring loom as needed.
PCM check: If wiring and valve check good, consult manufacturer procedures for PCM bench test or replacement; verify programming and perform final verification.
Clear codes and perform EVAP self-test/driving cycle to confirm repair.