P24BB

Code

Generic P — Powertrain

EVAP System Leak Detection Pump Pressure Sensor Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 24 EN: 37 RU: 22

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Page language: EN

Causes

Short to battery voltage on the pressure sensor signal circuit
Open or high-resistance ground for the sensor or LDP
Faulty EVAP leak detection pump (LDP) pressure sensor
Corroded, damaged, or poorly connected harness/connector at the sensor or pump
Blown fuse, damaged relay, or poor power supply to pump/sensor
Blocked EVAP vent or plumbing causing abnormal pressure (less common)

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Stored P24BB and possibly related EVAP codes
Possible failed emissions test (EVAP system fault)
No noticeable engine drivability change in many cases; may detect fuel odor if EVAP parts are open
EVAP pump may run continuously or not run when commanded (depending on underlying fault)

What to check

Read and record freeze frame and all stored EVAP-related codes with a scan tool
Visually inspect LDP, pressure sensor connector, and harness for damage, corrosion, pin push-out, or water intrusion
Check fuses and relays related to the EVAP/LDP circuit
Backprobe sensor connector with key ON and with pump commanded to observe voltages
Check for continuity to ground and for short to battery on the signal wire with connector disconnected
Verify pump operation by commanding LDP ON via scanner (observe pump power/ground and listen/measure current)

Signal parameters

Reference (sensor supply) voltage: typically ~5.0 V (check OE spec)
Pressure sensor signal: nominally varies proportionally with pressure; expected ~0.5–4.5 V range depending on design (consult vehicle service data)
A 'high' circuit usually shows a steady voltage near battery voltage (~12 V) or above normal maximum threshold
Ground circuit resistance: low continuity to chassis ground (typically
When pump is commanded, signal voltage should change; no change or steady high voltage indicates wiring or sensor fault

Diagnostic algorithm

Retrieve codes and freeze frame data; note history and related EVAP codes.
Perform visual inspection of the LDP assembly, harness, and connectors. Repair obvious damage.
With ignition ON (engine off), backprobe the sensor connector: verify reference voltage (~5 V), signal voltage, and ground presence. Record values.
Command the LDP ON using a scan tool and observe signal voltage change and pump power/ground. Listen for pump operation and measure current draw.
If signal voltage is high with connector plugged and reference absent or normal, disconnect the sensor and measure signal wire voltage to check for short to battery. A high voltage with sensor disconnected indicates wiring short to B+ or module output stuck high.
Check continuity between sensor ground and chassis ground; repair any high-resistance connection.
Wiggle harness and connectors while observing the signal for intermittent faults. Use a scope if available to view noise/transients.
If wiring checks good but signal remains incorrect, substitute a known-good LDP/pressure sensor or test the sensor per manufacturer procedure.
If replacement sensor and wiring are good and problem persists, test or replace PCM/ECM as a last resort after verifying all else.
After repairs, clear codes and perform a functional/road test; confirm no reappearance of P24BB and that EVAP routines complete.

Likely causes

Wiring harness short to battery on the pressure sensor signal
Corroded/loose connector at the LDP pressure sensor
Failed pressure sensor inside the leak detection pump assembly
Open/poor ground for sensor/pump
Failed LDP producing abnormal pressures that drive sensor out of expected range

Fault status

⚠️ Status

P24BB — EVAP Leak Detection Pump Pressure Sensor Circuit High. ECM detected sensor signal voltage above expected threshold indicating a possible short to battery, failed sensor, poor ground, wiring/connector issue, or less commonly a control module fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours