Fuel Tank Leak Detection Module - GX36-, Checking

General Description

The fuel tank has an integrated ventilation system in order to enable pressure equalization between the fuel tank and the environment when temperature variations occur or when fuel is added to or extracted from the tank. To prevent fuel evaporation to the atmosphere, a charcoal canister is installed between the fuel tank and the atmosphere. Since the charcoal canister has a limited storage capacity, it must be occasionally discharged into the intake manifold by using the evaporative emission (EVAP) canister purge valve for a short period of time. In systems without a turbocharger, an EVAP purge line from the canister purge valve to the intake manifold is sufficient. The Tank Leak Diagnostic Module (DM-TL) consists of an electrically operated air pump (DM-TL pump), an orifice with a defined diameter serving as a reference leak, and a change-over valve switching the air flow between the reference leak and the tank. If neither the pump nor the change-over valve is activated, the tank is ventilated through a bypass in the module. The canister purge valve can be actively checked using the DM-TL. For this purpose, the current consumption of the DM-TL pump is measured during a reference measurement and under different monitoring conditions. The pump current can be used to determine the pressure in the EVAP system and check the canister purge valve for proper operation.

The Fuel Tank Leak Detection Module -GX36- contains the following component:

Leak Detection Pump -V144-.

The Fuel Tank Leak Detection Module -GX36- components cannot be serviced separately, and they must be serviced as a unit.

Special tools and workshop equipment required

Multimeter.
Wiring Diagram.
Scan Tool.
Hand Vacuum Pump.
Evap Smoke Tester.

Test requirements

Fuses OK.
Battery voltage OK.
Switch OFF all electrical and electronic accessories.
Vehicles with automatic transmission, ensure the selector lever position is in "P".
Vehicles with manual transmission, ensure the shifter lever position is in "N" with the parking brake applied.
Observe all safety precautions: .
View clean working conditions: .

Test Procedure

Step	Procedure	Result / Action to Take
1	PERFORM: Preliminary Check to verify the customers complaint. Refer to . -- Was Complaint verified?	-- YES: GO TO: Step 2. -- NO: GATHER more information from customer about the complaint.
2	IGNITION: OFF. REMOVE: Evaporative Canister. Refer to appropriate Service Information. Plug or Cap off the Fuel Tank Leak Detection Module -GX36- port going to the vent filter. CONNECT: Hand vacuum pump to the Fuel Tank Leak Detection Module -GX36- CAN port and apply 0.700 bar and see if the vacuum holds. -- Did the vacuum hold?	-- YES: GO TO: Step 3. -- NO: REPLACE: Fuel Tank Leak Detection Module -GX36-. Refer to appropriate Service Information. GO TO: Step 5.
3	DISCONNECT: Fuel Tank Leak Detection Module -GX36- harness connector. IGNITION: ON. CHECK: Fuel Tank Leak Detection Module -GX36- harness connector terminal 4 to ground for voltage. IGNITION: OFF. SPECIFIED VALUE: Battery voltage. -- Was Value obtained?	-- YES: GO TO: Step 4. -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 5.
4	REMOVE: Engine/Motor Control Module -J623-. Refer to appropriate Service Information. CHECK: Fuel Tank Leak Detection Module -GX36- harness connector terminal 1 to the Engine/Motor Control Module -J623- harness connector T91 / 78 for resistance. CHECK: Fuel Tank Leak Detection Module -GX36- harness connector terminal 2 to the Engine/Motor Control Module -J623- harness connector T91 / 23 for resistance. CHECK: Fuel Tank Leak Detection Module -GX36- harness connector terminal 3 to the Engine/Motor Control Module -J623- harness connector T91 / 40 for resistance. SPECIFIED VALUE: 0.5 Ω (± 0.3 Ω). -- Were Values obtained?	-- YES: REPLACE: Fuel Tank Leak Detection Module -GX36-. Refer to appropriate Service Information. GO TO: Step 5. -- NO: PERFORM: Visual Inspection of wiring and component. CHECK: Wiring for open, high resistance, short or harness connector for damage, corrosion, loose or broken terminals. REPAIR: Faulty wiring or connector. GO TO: Step 5.
5	Final Procedure Perform a road test to verify repair. -- Does the original DTC return?	-- YES: CHECK: Engine/Motor Control Module -J623- harness connector for any damaged, pushed-out pins. REPAIR: As necessary. If all electrical connections are OK: REPLACE: Engine/Motor Control Module -J623-. Refer to appropriate Service Information. Clear the DTC's. Refer to . Repair is complete. Generate Readiness Code. Refer to . Return vehicle to Customer. -- NO: Perform the diagnostic procedure for any DTC's. If no DTC's return, the repair is complete. Return vehicle to customer.