EVAP System
EVAP System
=> [ EVAP System, Leak Detection ] EVAP System, Leak Detection
=> [ EVAP System, Checking for Leaks ] EVAP System, Checking For Leaks
=> [ EVAP Canister Purge Regulator Valve, Checking ] EVAP Canister Purge Regulator Valve, Checking
=> [ Leak Detection Pump, Checking ] Leak Detection Pump, Checking
For all EVAP system component locations and hose routing. Refer to repair information.
For the EVAP system hose routing. Refer to repair information.
For all EVAP system removal/installation procedures and torque specifications. Refer to repair information.
Check the Technical Bulletins for information that may supersede any information included in this service information. Refer to repair information.
• All manufacturers special tools as well as common tools may contain a manufacturer specific part number. These tools may be substituted with an equivalent aftermarket tool or are available for purchase through Audi.
• Manufacturers special tools as well as common tools that contain a manufacturer specific part number may be referenced in the test procedure illustrations showing the tool use or installation. If the manufacturer specific tool is not being used, an equivalent aftermarket tool may be installed in the same manner as the manufacturers special tool.
EVAP System, Leak Detection
Function
The leak detection system recognizes leaks in the complete fuel system, including the fuel tank, EVAP canister and the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80).
On the mechanical side, the leak detection system consists mainly of a vacuum-driven diaphragm pump equipped with a reed contact on the actuation rod of the pump diaphragm. The pump is supplied with vacuum via the engine intake stroke.
• When leak detection is activated, the diaphragm pump pumps the fuel system up to 20.. 30 mbar. The pump diaphragm is then moved out so that the reed contact at the operating rod remains in the "open" position.
• During the leak diagnosis, the reed contact is monitored to check if it remains open within 10 seconds. This indicates the system is sealed.
• If the pressure falls (indicating a leak), the diaphragm moves back and the reed contact closes.
• If the reed contact closes within 10 seconds of leak detection time, a further test is performed: In this case the diaphragm pump pumps four times again. The Motronic Engine Control Module (ECM) (J220) measures the time for each of the four pumps until the reed contact is closed again. From that, the control module can recognize a "small leak" (greater than 1 mm in diameter) or a "large leak".
Leak diagnosis is activated automatically shortly following every engine start. If a malfunction is determined, an entry is made to the Diagnostic Trouble Code (DTC) memory. The Malfunction Indicator Lamp (MIL) (K83) in the instrument cluster lights up if the malfunction is recognized for two subsequent starts.
EVAP System, Checking for Leaks
Special tools, testers and auxiliary items required
• Smoke tester.
• EVAP and Fuel Supply System Vacuum hose and line routing diagram.
• Secure all hose connections using hose clamps appropriate for the model type.
• Replace seals and gaskets when performing repair work.
Leak checking
- Using a Smoke tester, check the Evaporative Emission (EVAP) canister system for leaks.
• Always follow the manufacturers directions for the proper installation and operation of the Smoke tester being used.
If a leak is detected:
- Check the fuel filler cap seal for damage and for proper installation. Replace if necessary.
- Check the seals under the locking flanges and the union nuts are properly tightened on the fuel tank.
- Check all hose connections of the fuel supply system and replace or repair any leaking lines.
- Check all hose connections of the EVAP system and replace or repair any leaking lines.
- Repair or replace any damaged component.
If no leaks are found in the EVAP and Fuel Supply System:
- Erase the DTC memory if a DTC was set. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.
- Perform a road test to verify repair.
If a DTC was set and does not return:
Repair complete, Generate readiness code. Refer to => [ Readiness Code Description ] Readiness Code.
- End diagnosis.
If the DTC does return and no leaks are found in the EVAP and Fuel Supply System:
- Check the DTC memory for any DTC codes pertaining to the EVAP and Fuel Supply Systems. If a DTC is stored, perform the diagnostic test procedure for the suspected component. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.
End diagnosis.
EVAP Canister Purge Regulator Valve, Checking
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• The Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) fuse OK.
• The ignition switched off.
• Voltage for the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) is supplied via the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.
Start diagnosis
- Disconnect the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) electrical harness connector - 1 -.
Checking internal resistance
- Using a Multimeter, check the resistance between terminals 1 and 2 of the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80).
Specified value: 22,0 to 30,0 ohms.
If the specified value was not obtained:
- Replace the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80).
If the specification is obtained:
Checking voltage supply
- Using a Multimeter, check the electrical harness connector terminal 1 to 2 for voltage.
- Operate the starter briefly.
Specified value: battery voltage.
If the specified value was not obtained:
- Using a Multimeter, check the electrical harness connector terminal 1 to Ground (GND) for voltage.
- Operate the starter briefly.
Specified value: battery voltage.
If the specified value was not obtained:
- Check the wiring connection from the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for an open circuit according to wiring diagram.
If the specified value was not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the wiring connection.
If the specified value was obtained:
Check Ground (GND) activation
- Using a Multimeter, check the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) electrical harness connector to Battery positive (+) for voltage.
- Operate the starter briefly.
Specified value: battery voltage.
- Switch the ignition off.
If the specified value was not obtained:
If the manufacturers test box is being used. Perform the following step.
- Install the test box. Refer to repair information.
If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
- Using a Multimeter, check the Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80) electrical connector terminal 2 to the Motronic Engine Control Module (ECM) (J220) electrical connector T121 terminal 64 for an open circuit.
Specified value: 1.5 ohms.
If the specification was not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the wiring connection.
If the specification was obtained:
- Replace the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check the DTC memory.
2. If necessary, erase the DTC memory.
3. If the DTC memory was erased, generate readiness code.
- End diagnosis and switch the ignition off.
Leak Detection Pump, Checking
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• The Leak Detection Pump (LDP) (V144) fuse OK.
• The ignition switched off.
• The voltage for the Leak Detection Pump (LDP) (-V144-) is supplied via the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.
Start diagnosis
- Remove the left rear wheel housing liner. Refer to repair information.
- Disconnect the Leak Detection Pump (LDP) (V144) electrical harness connector - 3 -.
Checking internal resistance
- Using a Multimeter, check the Leak Detection Pump (LDP) (V144) for resistance as follows:
If the specifications was not obtained:
- Replace the Leak Detection Pump (LDP) (-V144-). Refer to repair information.
If the specified values are obtained:
Checking voltage supply
- Check the Leak Detection Pump (LDP) (-V144-) for voltage.
- Using a Multimeter, check the Leak Detection Pump (LDP) (-V144-) electrical harness connector terminal 3 to Ground (GND) for voltage.
- Operate the starter briefly.
Specified value: battery voltage.
- Switch the ignition off.
If the specified value was not obtained:
If the manufacturers test box is being used. Perform the following step.
- Install the test box. Refer to repair information.
If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
- Using a Multimeter, check the Leak Detection Pump (LDP) (-V144-)electrical harness connector terminal 3 to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) terminal 2/87 for an open circuit according to wiring diagram.
Specified value: Wire resistance 1.5 ohms.
If the specification was not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.
If no malfunction is detected in the wiring and if the voltage supply is OK:
Checking output wiring
- Using a Multimeter, check the Leak Detection Pump (LDP) (-V144-) electrical connector terminal 1 to Motronic Engine Control Module (ECM) (J220) electrical connector T121 terminal 25 for an open circuit.
- Using a Multimeter, check the Leak Detection Pump (LDP) (-V144-) electrical connector terminal 2 to Motronic Engine Control Module (ECM) (J220) electrical connector T121 terminal 94 for an open circuit.
Specified value: 1.5 ohms.
If the specification is not obtained:
- Check the wiring for a short circuit to Battery positive (+) or an open circuit.
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the wiring connection.
If no malfunction is found in wiring:
- Replace the Motronic Engine Control Module (ECM) (J220). Refer to => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.
Assembly is performed in the reverse order of the removal, note the following:
- Install the left rear wheel housing liner Refer to repair information.
Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.
- End of diagnosis.