P24C1

Code

Generic P — Powertrain

EVAP System Leak Detection Pump Switching Valve Performance/Stuck Off

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 89 RU: 33

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Page language: EN

Causes

Faulty EVAP leak detection pump switching valve (stuck mechanically or electrically)
Open/short/intermittent wiring or poor connector to the valve
Faulty ground or power supply (fuse, relay, harness damage)
Contamination or blockage in the EVAP valve/lines (dirt, fuel residue, collapsed hose)
Faulty EVAP leak detection pump or related solenoid affecting valve operation
PCM/ECU control fault or software anomaly (rare)

Symptoms

Malfunction Indicator Lamp (MIL) illuminated and P24C1 stored
Inability to complete EVAP system leak test or readiness not complete for EVAP monitor
Evap system warning message on cluster (model dependent)
Fuel odor in severe leaks (if EVAP lines compromised)
No change in valve state when commanded (observed with bi-directional tool)

What to check

Read stored codes and freeze frame with a capable scan tool; record EVAP-related readiness and live data
Verify the valve’s connector is fully seated, pins not corroded, and wiring insulation intact (visual and wiggle test)
Check fuses and any related relays for the EVAP pump/valve circuit
Command the switching valve with a bi-directional scan tool and note commanded vs reported state
Measure coil resistance at the valve connector (compare to manufacturer spec or typical range)
Back-probe connector for supply voltage and ground while commanding the valve ON and OFF

Signal parameters

Control type: PCM commanded (ground or +12V depending on design) or PWM in some systems
Typical coil resistance: commonly tens of ohms (example range 10–100 Ω) — verify service spec
Supply voltage with valve commanded ON: near battery voltage (9–14 V) or ground switched to complete circuit depending on design
Command signal: ON/OFF or PWM duty cycle (0–100% for PWM systems) visible on scan tool
Response: valve state should change within a few hundred milliseconds to a second when commanded
Line pressure/vacuum change expected when valve operates during EVAP leak test

Diagnostic algorithm

Verify the DTC with a scan tool and clear codes. Attempt to re-run EVAP test to re-check code appearance and capture data.
Visually inspect the valve, connector, and harness for damage, corrosion, or disconnection. Repair obvious wiring damage before further testing.
With key ON (engine off) back-probe the valve connector. Command valve ON with a bi-directional tool and observe: supply voltage and ground presence, and compare to OFF state.
Measure valve coil resistance (engine off, connector disconnected). If open or far out of expected range, replace valve.
If coil resistance is OK, apply fused bench voltage (or use vehicle command) to verify mechanical operation — listen for click or check for flow change. Do not apply unprotected voltage without proper fuse and procedure.
If valve electrically operates but system still fails, pressure/vacuum test EVAP lines and perform smoke test to find blockages or leaks that could prevent valve movement or function.
Inspect/verify operation of the leak detection pump and any related solenoids (a failed pump may cause related switching faults).
Check fuses and relays for the EVAP circuit and check PCM grounds and power feeds. Repair wiring as needed.
If wiring, valve, pump, and fuses are good but code persists, consult manufacturer service information for PCM test procedures and consider ECU-related diagnostics or software updates.
After repairs, clear codes and confirm proper EVAP monitor operation by re-running the leak test and verifying readiness status.

Likely causes

Stuck or failed switching valve (electrical coil or mechanical plunger)
Broken or corroded connector/wiring to the valve
Blocked or collapsed EVAP hose or lines preventing valve movement
Blown fuse or faulty power/ground to valve

Fault status

⚠️ Status

Malfunction Indicator Lamp (MIL) illuminated. EVAP system leak detection pump switching valve performance fault detected; DTC stored. EVAP monitor may be unavailable or incomplete until fault is resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 3.0 hours