P0451

DTC P0451 EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE SENSOR/SWITCH RANGE/PERFORMANCE

MONITOR DESCRIPTION

DTC Detection Condition:

DTC P0450 or P0451 is recorded by the ECM when the vapor pressure sensor malfunctions.

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

P0451
The ECM sensor pressure in the fuel tank using the vapor pressure sensor. The ECM supplies the sensor with a regulated 5 V reference voltage and the sensor returns a signal voltage between 0.5 V and 4.5 V according to the pressure level in the fuel tank.

When the pressure in the fuel tank is low, the output voltage of the vapor pressure sensor is low. When it is high, the output voltage is high.

For DTC P0451, the ECM checks for a "noisy" sensor or a "stuck" sensor.

The ECM checks for a "noisy" sensor by monitoring the fuel tank pressure when the vehicle is stationary and there should be little variation in the tank pressure. If the indicated pressure varies beyond specified limits, the ECM will illuminate the MIL (2-trip detection logic) and a DTC is set.

The ECM checks for a "stuck" sensor by monitoring the fuel tank pressure for an extended time period. If the indicated pressure does not change over this period, the ECM will conclude that the fuel tank pressure sensor is malfunctioning. The ECM will then illuminate the MIL and a DTC is set.

Wiring Diagram:

Typical Malfunction Thresholds:

Step 2 - 3:

INSPECTION PROCEDURE

HINT:
- If DTC P0441, P0446, P0450 or P0451 is output after DTC P0442, first troubleshoot DTC P0441, P0446 P0450 or P0451. If no malfunction is detected, troubleshoot DTC P0442 next.
- Read freeze frame data using the hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

CHECK FOR INTERMITTENT PROBLEMS

Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect when the ECM is in check mode. In check mode, the ECM uses 1 trip detection logic, which has a higher sensitivity to malfunctions than normal mode (default), which uses 2 trip detection logic.

a. Clear the DTCs.
b. Change to check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Wiggle the harness and connector.