Evaporative Emission Control System Diagnosis. Cadillac Concours 1997

For 1990-2009 cars

### Diagnostic Codes

Diagnostic trouble codes P0441, P1441 and P1645 relate directly to EVAP system components and should be diagnosed before proceeding with other diagnosis.

### EVAP System Charcoal Contamination Checking Procedure

1. Remove EVAP Purge solenoid and the EVAP vacuum switch. Refer to R&R Procedures .
2. Lightly tap both components on a hard surface.
3. Check for the release of charcoal from either component.
4. If charcoal contamination is present replace the EVAP Vapor canister, EVAP Purge solenoid, EVAP Vacuum switch and clean the EVAP purge hoses. Refer to the EVAP Purge Hose Cleaning Procedure .

### EVAP Purge Hose Cleaning Procedure

1. Verify charcoal contamination by performing the EVAP System Charcoal Contamination Checking Procedure .
2. Disconnect the EVAP Vapor canister purge hose.
3. Disconnect the hoses from the EVAP Purge solenoid and the EVAP vacuum switch.
4. Disconnect the pressure hose (knurled nut) from the EVAP Pressure Cart (J 41413) leaving one end connected to the nitrogen tank.
5. Using a short piece of tubing, fabricate a nozzle on the loose end of the pressure hose.

Important: Never substitute compressed air for the nitrogen tank.

6. Using the fabricated nozzle, apply nitrogen for 15 seconds to each EVAP purge hose until all hoses have been cleaned.
7. Reassemble the EVAP Pressure Cart (J 41413).
8. Reconnect the EVAP purge hoses.

### EVAP Charcoal Canister

Attach a hose to the fuel vapor port (from fuel tank) of the canister and attempt to blow through it. Air should pass into canister. If not, replace the canister.

Attach a hose to the EVAP port (from engine mounted solenoid) of the canister, and attempt to blow through it. Air should not pass into the canister. If air passes, replace canister.

Reconnect all hoses.

### EVAP Solenoid

The EVAP solenoid receives 12 volts from an ignition fed 10 amp fuse. The PCM energizes the EVAP solenoid by grounding connector C2, pin 24. When the solenoid is energized it allows the canister to purge.

Attach hose to vapor line that comes from canister to solenoid and attempt to blow into it. Air should not pass into solenoid. If air passes through solenoid, then replace solenoid.

With engine OFF, go into EVAP solenoid override. Override of solenoid should cause solenoid to vibrate. Physically touch solenoid, mounted in engine compartment, in override condition. If solenoid is not vibrating, then replace solenoid.

### EVAP Purge Vacuum Switch

The EVAP vacuum switch is located in the vacuum line between the EVAP canister and the EVAP solenoid. The switch is normally closed and opens with a sufficient amount of vacuum. The switch is used as an input to the PCM, informing the PCM if the EVAP solenoid is open or closed. The EVAP vacuum switch input is HI (12 volts) when the switch contacts are open, and LO (0 volt) when the switch contacts are closed.

Disconnect the purge vacuum switch hose that goes to the purge solenoid. With a hand-held vacuum pump connected to the switch vacuum port, draw a vacuum. The vacuum should bleed off. If not, there is a restriction in the EVAP purge hose from the canister. With vacuum drawn at the sensor, the vacuum switch should be open when checked with either a diagnostic scan tool or electrically with a voltmeter.