Grand AM L4-144 2.4L DOHC VIN T SFI (1997)
Diagnosis
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The EVAP system can be diagnosed by using EVAP Control System Diagnosis.
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EVAP canister purge valve operation is covered and diagnosed in DTCs P0440, P0446, and P1441.
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EVAP vent solenoid operation is covered and diagnosed in DTCs P0440, P0442, and P0446.
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Fuel tank vapor pressure sensor operation is covered and diagnosed in DTCs P0440, P0442, P0446, P1441 and Evaporative Emission System
Check.
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A open or shorted circuit in the EVAP canister purge valve and EVAP vent solenoid can also be diagnosed in PCM Outputs Diagnosis.
Visual Check of the EVAP Canister
If cracked or damaged, replace canister.
Circuit Description
The fuel tank vapor pressure sensor is used to detect vacuum decay and excess vacuum during the EVAP diagnostic routine. The sensor responds to
changes in fuel tank pressure or vacuum. The signal voltage to the PCM varies from a minimum of about 0.2 volts with pressure in the fuel tank to above
4 volts with a high vacuum in the fuel tank.
The Fuel Tank Vacuum Pressure display on the scan tool has an auto zero feature which occurs at each ignition cycle and is corrected according to
barometric pressure. Because of this, Fuel Tank Vacuum Pressure may not accurately reflect the actual output of the sensor or conditions within the fuel
tank.
Table C-3C is intended to isolate and diagnose electrical problems with the sensor wiring or the sensor.
Diagnostic Aids
Check for the following conditions:
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Inspect the PCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and
for poor terminal to wire connections.
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Inspect the wiring harness for damage. If the harness appears to be OK, observe the Fuel Tank Vacuum Pressure display on the scan tool while
moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.
Test Description
1. The Powertrain OBD System Check prompts the technician to use the Capture Info. selection on the scan tool. This creates an electronic copy of
the freeze frame data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. Refer to Fuel Delivery and Air Induction for fuel tank removal.
5. A normal fuel tank pressure sensor voltage output with no pressure or vacuum on the fuel system should be between 1.3 V and 1.7 V.
14. The replacement PCM must be programmed and the crankshaft position system variation procedure must be preformed. Refer to the latest
Techline procedure for PCM reprogramming and also refer to the Crankshaft Position System Variation Procedure.
