2010 Cadillac Truck SRX FWD V6-3.0L Page 1509

2010 Cadillac Truck SRX FWD V6-3.0L Page 1509

Circuit/System Description

The fuel tank pressure sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The engine control module (ECM)

supplies a 5V reference and a low reference circuit to the fuel tank pressure sensor. The fuel tank pressure sensor signal voltage varies depending

on EVAP system pressure or vacuum. The controller also uses this fuel tank pressure signal to determine atmospheric pressure for use in the

engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed.

Conditions for Running the DTC

P0451

* DTC P0451 runs only when the engine-off natural vacuum small leak test, P0442, executes.

* The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes.

P0452 and P0453

DTC P0452 and P0453 run continuously when the ignition is ON.

P0454

* DTC P0454 runs only when the engine-off natural vacuum small leak test, P0442, executes.

* This test can run once per engine-off period. The length of the test can be up to 10 minutes.

* A refueling event is not detected.

Conditions for Setting the DTC

P0451

This DTC will set if the controller is unable to re-zero the fuel tank pressure sensor voltage within a calibrated range during the engine-off small

leak test, P0442.

P0452

The fuel tank pressure sensor voltage is less than 0.1V for more than 5 seconds.

P0453

The fuel tank pressure sensor voltage is more than 4.9V for more than 5 seconds.

P0454

If, during the engine-off natural vacuum small leak test, P0442, the ECM detects an abrupt fuel tank pressure signal change, other than a refueling

event, this DTC will set. An abrupt change is defined as a change of 0.45 inch H2O in the span of 1 second.

Action Taken When the DTC Sets

* DTCs P0451 and P0454 are Type A DTCs.

* DTCs P0452 and P0453 are Type B DTCs.

Conditions for Clearing the MIL/DTC

* DTCs P0451 and P0454 are Type A DTCs

* DTCs P0452 and P0453 are Type B DTCs

Diagnostic Aids

P0451 and P0454

* A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot

bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set.

* Ensure that the reference port on the fuel tank pressure sensor is unobstructed.

* An fuel tank pressure sensor that is skewed or does not have a linear transition from low to high may cause this code to set. Scan tool output