P24B9

Code

Generic P — Powertrain

EVAP System Leak Detection Pump Pressure Sensor Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 62 RU: 31

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Page language: EN

Causes

Open or short in sensor wiring (signal, reference, or ground)
Corroded or loose connector at the pressure sensor or pump assembly
Faulty EVAP leak detection pump pressure sensor
Faulty leak detection pump or pump plumbing restricting pressure change
Blocked or leaking EVAP lines or fittings affecting pressure readings
Intermittent ECM/PCM fault or poor ground at control module

Symptoms

MIL/Check Engine light illuminated
Unable to complete EVAP system self-test or monitor
Possible failed EVAP leak test entries in readiness data
Occasional drivability unaffected — no fuel smell is typical unless large leak present

What to check

Read and record freeze frame and live data for EVAP pump pressure sensor while performing EVAP test or commanding pump on
Visually inspect sensor connector and wiring for damage, corrosion, or water ingress
Check for proper reference voltage (typically 5 V) and ground at the sensor connector with engine off and key on
Backprobe signal wire; verify sensor voltage changes when pump is commanded or system is actuated
Perform continuity/resistance checks between sensor connector and ECM pins
Scan for related EVAP codes (P0452/P0453/P0442/P0455/P0446) and cross-check symptoms

Signal parameters

Reference (Vref) typically 5 V supplied by ECU (verify for vehicle)
Sensor signal nominal range often ~0.5–4.5 V depending on pressure (verify factory spec)
At open atmosphere the sensor should read a stable baseline voltage; during pump actuation voltage should move consistently within expected range
No rapid voltage oscillation, stuck at near 0 V, or pinned to Vref (5 V) under test

Diagnostic algorithm

Record DTC, freeze frame, and live data. Note conditions when code set (temperature, engine off/on, pump commanded).
Perform a visual inspection of the leak detection pump assembly, pressure sensor connector, harness routing, and EVAP lines for damage or contamination.
With key ON (engine off), backprobe sensor connector: verify Vref (≈5 V) on reference pin and a good ground. If Vref or ground missing, suspect ECU wiring or ECU.
Command the EVAP leak detection pump ON with a scan tool while monitoring the pressure sensor signal. Confirm the signal moves smoothly and within spec. If signal is stuck or out of range, suspect sensor or wiring.
Check continuity between sensor ground and vehicle chassis ground and between sensor Vref and ECU Vref pin. Repair any high resistance or opens.
Wiggle test the harness and connectors while monitoring live data to reveal intermittent faults. Repair/replace connectors or wiring as needed.
If wiring and connectors test good, replace the pressure sensor or the leak detection pump assembly per manufacturer procedure and re-test.
After any repair, clear codes and run the EVAP monitor/self-test or perform a smoke test to verify system integrity and that code does not return.
If fault persists with known-good sensor and wiring, inspect ECM grounds and consider ECU/PCM diagnosis or replacement per factory guidance.

Likely causes

Damaged wiring or pin corrosion at sensor connector
Defective pressure sensor in the leak detection pump assembly
Internal pump failure or clogged EVAP plumbing producing abnormal pressure
Poor sensor ground or missing reference voltage from ECM

Fault status

⚠️ Status

The EVAP leak-detection pump pressure sensor circuit is producing a signal outside expected range or not performing within expected parameters during EVAP pump operation. This may be caused by wiring/connectors, a failed sensor or pump, blocked EVAP plumbing, or an ECU-related issue.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours