Multiport Fuel Injection (mfi) - 3.7l & 4.2l v8 4v (aew, Abz) Audi A8 D2

Safety precautions

Rules of cleanliness

1. Thoroughly clean fuel system line and hose connections and the surrounding area before disconnecting.
2. Place removed components on a clean surface and cover. Use plastic sheeting or paper. Do not use fluffy rags that could leave lint!
3. Carefully cover over or seal any components that have been opened if repairs are not carried out immediately.
4. Install only clean parts: Do not remove replacement parts from the packaging until immediately before they are to be installed. Do not use parts that have been stored without packaging (for example, in toolboxes, etc.).
5. When the fuel system is opened: Avoid working with compressed air whenever possible. Avoid moving the vehicle if possible.

Technical data

1. To check fuel pressure, see «FUEL PRESSURE REGULATOR AND RESIDUAL FUEL PRESSURE, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__fuel-pressure-regulator-and-residual-fuel) .

Technical Data. Scheme 36

Component locations, overview

Note. The following list refers to items in (Scheme 37).

1. Power output stage - N122- and power output stage 2 -N192
2. Engine Control Module (ECM) -J220
3. Fuses and relays Fuses for Motronic Motronic Engine Control Module (ECM) power supply relay -J271
4. Harness connector Connector for: Heated Oxygen Sensor (HO2S) -G39- Oxygen Sensor (O2S) heater -Z19- Bank 1 NOTE: The connector for Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- and O2S heater -Z29- (bank 1) is located under the right front carpet. See «OXYGEN SENSOR (O2S) HEATING, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-heating-checking) .
5. Heated Oxygen Sensors (HO2S), Oxygen Sensor (O2S) heaters (bank 1) HO2S -G39- O2S heater -Z19- O2S behind TWC -G130- O2S heater -Z29
6. Engine Coolant Temperature (ECT) sensor -G62- Rear of cylinder head
7. Intake Air Temperature (IAT) sensor -G42
8. Throttle Position (TP) sensor -G69- With integrated Closed Throttle Position (CTP) switch -F60
9. Idle Air Control (IAC) valve -N71
10. Engine Speed (RPM) sensor -G28
11. Harness connector Connector for: Heated Oxygen Sensor (HO2S) 2-G108- Oxygen Sensor (O2S) heater -Z28- Bank 2 NOTE: The connector for Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) 2 -G131- and O2S 2 heater -Z30- (bank 2) is located under the right front carpet. See «OXYGEN SENSOR (O2S) HEATING, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-heating-checking) .
12. Harness connector Connector for Engine Speed (RPM) sensor - G28
13. Heated Oxygen Sensors (HO2S), Oxygen Sensor (O2S) heaters (bank 2) HO2S 2-G108- O2S 2 heater -Z28- O2S 2 behind TWC - G131- O2S 2 heater -Z30
14. Camshaft Position (CMP) sensor -G40
15. Knock Sensor (KS) 2 - G66
16. Ignition coils (bank 2) Cyl. 5: -N164- Cyl. 6: -N189- Cyl. 7: -N190- Cyl. 8: -N191
17. Fuel injectors (bank 2) Cyl. 5: -N83- Cyl. 6: -N84- Cyl. 7: -N85- Cyl. 8: -N86
18. Air control valve for fuel injectors -N212
19. Intake Manifold Tuning (IMT) valve -N156
20. Knock Sensor (KS) 1 - G61
21. Fuel injectors (bank 1) Cyl. 1: -N30- Cyl. 2: -N31- Cyl. 3: -N32- Cyl. 4: -N33
22. Ignition coils (bank 1) Cyl. 1: -N- Cyl. 2: -N128- Cyl. 3: -N158- Cyl. 4: -N163
23. Evaporative Emission (EVAP) canister purge regulator valve -N80
24. Mass Air Flow (MAF) sensor -G70- In Air Cleaner (ACL) housing, upper

Identifying Motronic Multiport Fuel Injection System Components. Scheme 37

Intake air system with Mass Air Flow (MAF) sensor

Note. The following list refers to items in (Scheme 38).

Scheme 38

1. Air Cleaner (ACL) housing, upper
2. Intake air connecting hose
3. Intake air duct
4. Hose For air control valve for fuel injectors -N212
5. Intake air connecting hose
6. Air Cleaner (ACL) housing, lower
7. Air Cleaner (ACL) element
8. Intake air duct
9. Seal
10. Mass Air Flow (MAF) sensor -G70
11. Seal (Scheme 38): Exploded View Of Intake Air System With Mass Air Flow (MAF) Sensor

Fuel rail and fuel injectors

1. See safety precautions under «MOTRONIC MULTIPORT FUEL INJECTION (MFI) SYSTEM, SERVICING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .
2. See «RULES OF CLEANLINESS»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__rules-of-cleanliness) .

Note. Before starting repairs, check Diagnostic Trouble Code (DTC) memory. See Check Diagnostic Trouble Code (DTC) Memory, (scan tool function 02) . Check output Diagnostic Test Mode (DTM). See OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03) . Always replace seals and gaskets.

Note. The following list refers to items in (Scheme 39).

1. Fuel supply line 25 Nm (18 ft lb)
2. Fuel return line 25 Nm (18 ft lb)
3. Fuel pressure regulator
4. O-ring Always replace
5. Vacuum unit for cruise control
6. 20 Nm (15 ft lb)
7. Retaining clip for fuel injector
8. Air-shrouded fuel injector Always replace O-ring NOTE: When replacing O-ring, do not remove cap.
9. 10 Nm (7 ft lb)
10. Fuel rail
11. 10 Nm (7 ft lb)
12. Vacuum hose
13. Retaining clip for fuel pressure regulator

Exploded View Of Fuel Rail And Fuel Injectors. Scheme 39

Dual-stage intake manifold with intake manifold change-over valve

1. Read safety precautions under «MOTRONIC MULTIPORT FUEL INJECTION (MFI) SYSTEM, SERVICING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .
2. See «RULES OF CLEANLINESS»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__rules-of-cleanliness) .

Note. Before starting repairs, check CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02) and OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03) .

Note. The following list refers to items in (Scheme 40).

1. Intake manifold With intake manifold change-over valve -N156
2. 25 Nm (18 ft lb)
3. 20 Nm (15 ft lb)
4. 15 Nm (11 ft lb)
5. Throttle body
6. Gasket Always replace
7. Throttle Position (TP) sensor -G69- With integrated Closed Throttle Position (CTP) switch -F60
8. Flange
9. Idle Air Control (IAC) valve -N71
10. 10 Nm (7 ft lb)
11. 5 Nm (44 in. lb)
12. 15 Nm (11 ft lb)
13. Angled intake air connector housing
14. O-ring
15. 25 Nm (18 ft lb)
16. Vacuum unit Nut: 15 Nm (11 ft lb)
17. Vacuum hose
18. Connecting rod
19. Intake Manifold Tuning (IMT) valve -N156
20. 10 Nm (7 ft lb)
21. Air control valve for fuel injectors -N212

Exploded View Of Dual-Stage Intake Manifold With Intake Manifold Change-Over Valve. Scheme 40

VAG1598/19 test box, connecting

Note. If the Engine Control Module (ECM) is equipped with a metal anti-theft housing (for theft prevention), the metal anti-theft housing must be removed from the ECM to connect the test box. See ENGINE CONTROL MODULE (ECM) (WITH METAL ANTI-THEFT HOUSING), REPLACING . After repairs are complete, the metal anti-theft housing must be reinstalled. VAG1598/19 must not be connected during diagnostic testing using the VAG1551 Scan Tool (ST). Wait at least 10 seconds after switching the ignition off before disconnecting the Engine Control Module (ECM) harness connector. When the ECM is disconnected, the ECM's learned values are erased, but malfunctions stored in DTC memory are retained. After reconnecting the ECM, check engine basic settings. See BASIC SETTING, (SCAN TOOL FUNCTION 04) . Generate readiness code. See READINESS CODE, GENERATING .

1. Switch ignition off.
2. Disconnect Engine Control Module (ECM).
3. Connect VAG1598 test box with adapter cable VAG1598/19 to ECM wiring harness.

Engine Control Module (ECM) (without metal anti-theft housing), replacing

For ECM's with metal anti-theft housing, see ENGINE CONTROL MODULE (ECM) (WITH METAL ANTI-THEFT HOUSING), REPLACING .

Note. When the ECM is disconnected, the ECM's learned values are erased, but malfunctions stored in DTC memory are retained. After installing and connecting the new ECM: Check ECM coding. See ENGINE CONTROL MODULE (ECM) CODING, CHECKING . Check engine basic settings. See BASIC SETTING, (SCAN TOOL FUNCTION 04) . Generate readiness code. See READINESS CODE, GENERATING . During the initial learning phase during basic engine adjustment, the engine idle speed may not be stable and there may be some slight hesitation while driving.

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and check ECM coding. See «ENGINE CONTROL MODULE (ECM) CODING, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__engine-control-module-ecm-coding-checking) .

Indicated on display: ECM identification and coding (example: 4.2 liter engine)

Scheme 41

1. Print ECM identification and check coding. See «ENGINE CONTROL MODULE (ECM) CODING, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__engine-control-module-ecm-coding-checking).
2. Press -->button to advance program sequence. (Scheme 41): VAG1551 Or VAG1552 Scan Tool Display - Engine Control Module Coding (Example)
3. Switch ignition off, wait at least 10 seconds, then disconnect harness connector from ECM. Location of ECM. See «COMPONENT LOCATIONS, OVERVIEW»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__component-locations-overview).
4. Install new ECM.

After installation of new ECM

1. Check coding of new ECM. See «ENGINE CONTROL MODULE (ECM) CODING, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__engine-control-module-ecm-coding-checking) .
2. Check Diagnostic Trouble Code (DTC) memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) .
3. Check engine basic settings. See «BASIC SETTING, (SCAN TOOL FUNCTION 04)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__basic-setting-scan-tool-function-04) .
4. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Engine Control Module (ECM) (with metal anti-theft housing), replacing

For ECM's without metal anti-theft housing, see ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING .

Note. Adaptation values are erased when the harness connector is disconnected from the Engine Control Module (ECM). The Diagnostic Trouble Code (DTC) memory content remains intact.

Scheme 42

Scheme 43

1. Connect VAS5051 tester and select vehicle system "01 - Engine Electronics". Ignition must be switched on for this. VAS5051 tester display will indicate the control module identification and coding -2-. (Scheme 42): VAS5051 Tester Display - Engine Control Module
2. Always allow display of control module identification first and print it out.
3. Switch ignition off.
4. Remove cover of E-box for control modules in plenum chamber (right side).
5. Remove Engine Control Module (ECM). (Scheme 43): Removing Cover Of E-Box For Control Modules In Plenum Chamber

To restrict accessibility (for theft prevention) to the harness connectors and the Engine Control Module (ECM), the ECM -1- is screwed to a metal anti-theft housing -4- via a locking mechanism -2- and snap-off screws -3-. (Scheme 44)

The threads of the snap-off screws are coated with locking compound to make it more difficult to remove the snap-off screws.

Identifying Engine Control Module With Metal Anti-Theft Housing. Scheme 44

To disconnect the harness connectors from the Engine Control Module (ECM) (for example, when connecting a test box or when replacing the ECM), the ECM must be removed from the metal anti-theft housing. This procedure is described as follows.

The following equipment is required

Scheme 45

1. Heat gun -1- (from VAS1978 Wiring Harness Repair Kit)
2. Adapter nozzle -2- (also from VAS1978 Wiring Harness Repair Kit)
3. Standard locking pliers (Scheme 45): Identifying Special Tool

Procedure

Scheme 46

Scheme 47

Scheme 48

Scheme 49

Scheme 50

1. "Flip" the Engine Control Module (ECM) with anti-theft housing in direction of the engine compartment so that the locking mechanism (item -2- in illustration) becomes visible and place a clean rag below the Engine Control Module (ECM) with anti-theft housing. (Scheme 46): Identifying Engine Control Module With Metal Anti-Theft Housing
2. Adjust the heat gun as shown in illustration, i.e. temperature adjustment -2- to maximum heat output and the two-stage switch for air mass -3- to position 3. (Scheme 47) NOTE: Next, use a heat gun to heat the threads of the locking mechanism in which the snap-off screws are screwed into. This step loosens the locking compound on the thread of the snap-off screws for easier removal. WARNING: By heating the locking mechanism threads, the snap-off screws and parts of the metal anti-theft housing will also become very hot. Be careful not to get burned! If possible, also make sure that only the threads are no parts that are in the vicinity become heated. If necessary, cover them. (Scheme 47): Identifying Heating Control Switch
3. Guide nozzle -1- of the heat gun to the locking mechanism threads so that the nozzle "encloses" the threads. It is OK to let the nozzle make contact at the upper end of the metal anti-theft housing.
4. Switch on heat gun and heat up threads for approx. 20 to 25 seconds. (Scheme 48): Applying Heat Gun To ECM Locking Mechanism Threads
5. Next, using locking pliers -1-, grab screw head -2- and snap-off screw by turning in direction of arrow. (Scheme 49) Procedure for the second snap-off screw is exactly the same. Be very careful since the control module connector is in close proximity. (Scheme 49): Using Locking Pliers, Grab Screw Head
6. Guide nozzle -1- of the heat gun to the locking mechanism threads again so that the nozzle "encloses" the threads. It is OK to let the nozzle make contact at the upper end of the metal anti-theft housing.
7. Switch on heat gun and heat up thread for approx. 20 to 25 seconds. (Scheme 50): Guiding Nozzle -1- Of The Heat Gun To The ECM Locking Mechanism Threads
8. Next, using locking pliers -1-, grab screw head -2- and remove snap-off screw by turning in direction of arrow. see scheme 16: Using Locking Pliers -1-, Grab Screw Head The Engine Control Module (ECM) can now be removed from the metal anti-theft housing.
9. Disengage connectors from Engine Control Module (ECM) and then disconnect connectors.
10. Remove old Engine Control Module (ECM) and insert new one.

Installing Engine Control Module (ECM)

Installation is the reverse order of removal, noting the following

After repairs are complete, the metal anti-theft housing must be reinstalled. Use new snap-off screws.

After connecting a new Engine Control Module (ECM), the following work steps must be performed

1. Activate Engine Control Module (ECM) in "Guided Troubleshooting" below the subject heading "Engine Control Module (ECM), replacing".

Use VAS5051 tester to do so.

Engine idle speed and CO content, checking

Note. The engine idle speed, ignition timing and CO content are not adjustable. Engine idle speed is maintained at a specified value by the Idle Air Control (IAC) valve and the digital idle speed stabilization function of the ECM. CO content is maintained at a specified value by Oxygen Sensor (O2S) control. Malfunctions in O2S control are detected by the On Board Diagnostic (OBD) system and stored in Diagnostic Trouble Code (DTC) memory. Checking CO content before the Three Way Catalytic Converters (TWC) is not possible. When the ECM or the battery is disconnected, all learned values will be erased. Check engine basic settings. See BASIC SETTING, (SCAN TOOL FUNCTION 04) .

Requirements

1. Engine coolant temperature at least 85°C (185°F)
2. All electrical consumers switched off (radiator coolant fan must not be running while checking idle speed)
3. A/C switched off
4. Automatic transmission selector lever in P or N position.

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . CAUTION: The radiator coolant fan must not run.

Indicated on display

VAG1551 Or VAG1552 Scan Tool Display - Engine Idle Speed CO Content (1 Of 3). Scheme 51

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 Or VAG1552 Scan Tool Display - Engine Idle Speed CO Content (2 Of 3). Scheme 52

1. Press buttons -0-, -0- and -5- to input display group number 5 (005), and press -Q- button to confirm input.

Indicated on display

VAG1551 Or VAG1552 Scan Tool Display - Engine Idle Speed CO Content (3 Of 3). Scheme 53

1. Check specified engine idle speed values (display fields 1-2). (Scheme 54) (Scheme 54): Display Group 5: Engine Idle Speed Values
2. Press --> button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Fuel pressure regulator and residual fuel pressure, checking

The fuel pressure regulator maintains fuel pressure relative to the intake manifold pressure.

1. Fuel Pump (FP) relay OK
2. Fuel pump OK
3. Air Cleaner (ACL) element OK
4. Battery Positive Voltage (B+) OK

Scheme 54

Scheme 55

1. Open fuel filler cap, and close again (to release pressure). WARNING: Fire Hazard! The fuel system is under pressure. Before disconnecting fuel lines or opening test connections, cover the connections with a rag to absorb discharged fuel. Carefully release pressure by slowly disconnecting the hose, or by opening the fuel filler cap to release pressure.
2. Before opening connection (arrow), cover with rag to prevent fuel spray. (Scheme 55): Fuel Pressure Pipes
3. Install fuel pressure gauge VAG1318 with adapters VAG1318/11 and VAG1318/12 in fuel supply line. NOTE: VAG1318 must be installed with the shut off valve between the gauge and the fuel rail for proper evaluation of residual pressure tests. Valve on pressure gauge must be open (lever in direction of flow).
4. Start engine and run at idle. Specified value: approx. 3.6 bar (52 psi) NOTE: If fuel pressure is not released, check whether fuel supply and fuel return lines have been interchanged.
5. Disconnect vacuum hose (arrow) for fuel pressure regulator. (Scheme 56): Disconnecting Vacuum Hose (Arrow) For Fuel Pressure Regulator
6. Fuel pressure must increase to approx. 4.2 bar (61 psi).
7. Switch ignition off.
8. Check residual pressure by observing pressure reduction. After 10 minutes at least 3 bar (44 psi) pressure must still be indicated on gauge. If residual pressure drops below 3.0 bar (44 psi)
9. Start engine and stop engine after fuel pressure has built up.
10. Close valve on fuel pressure gauge VAG1318.

If residual fuel pressure holds

1. Connection between fuel pressure gauge and fuel pressure regulator leaking.
2. Fuel pressure regulator leaking; replace if necessary.
3. For fuel injectors leaking, see «FUEL INJECTION VOLUME, FUEL INJECTOR LEAKAGE AND SPRAY PATTERN, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .

If residual fuel pressure drops again

1. Connection between fuel pressure gauge and fuel supply line leaking.
2. Fuel supply line at fuel tank leaking.
3. Check valve in fuel pump leaking. See «FUEL PUMP CHECK VALVE, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#fuel-supply-37l-42l-v8-4v-aew-abz__fuel-pump-check-valve-checking) .

Note. Before disconnecting the fuel pressure gauge, close the valve, disconnect line at VAG1318/12 adapter, and pour left-over fuel into suitable container by opening valve.

1. Fuel pressure OK

Preparation

1. Remove intake air duct between air cleaner housing and throttle valve.
2. Remove engine cover.
3. Remove accelerator pedal cable at bracket.
4. Remove ball joint at connecting linkage for cruise control.
5. Move accelerator pedal cable over cruise control vacuum unit toward rear.
6. Disconnect vacuum hose for cruise control vacuum unit.
7. Disconnect vacuum hose from fuel pressure regulator.
8. Disconnect harness connector for engine coolant temperature sensor (blue connector).
9. Disconnect harness connectors for knock sensors. Remove cable ties or retaining straps as necessary.
10. Disconnect connector for Intake Manifold Tuning (IMT) valve.
11. Disconnect harness connector for air control valve for fuel injectors.
12. Disconnect harness connectors from fuel injectors. Remove cable ties or retaining straps as necessary.
13. Remove fuel rail from intake manifold and lift off together with fuel injectors.
14. Disconnect hose from air control valve for fuel injectors.
15. Connect VAG1598/19 test box to wiring harness connector for Engine Control Module (ECM). See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .

Checking fuel injector leakage

1. Using adapter cables from VAG1594 connector test kit, connect jumper wire between VAG1598/19 test box terminals D11 and A4 (to actuate fuel pump relay).
2. Switch ignition on.
3. Visually check fuel injectors for leaks. With the fuel pump running, no more than 1 to 2 drops per minute may drip from the fuel injectors.
4. Switch ignition off.

If fuel leakage is greater than 1 to 2 drops per minute

1. Stop fuel pump (disconnect jumpered connection on VAG1598/19 test box) and replace faulty injector(s).
2. Install fuel rail. See «INSTALLING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__installing) .
3. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Checking fuel injection volume

Note. Before removing fuel injectors, release fuel pressure by briefly opening and closing fuel filler cap.

Scheme 56

1. Remove fuel rail. See «FUEL INJECTION VOLUME, FUEL INJECTOR LEAKAGE AND SPRAY PATTERN, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz).
2. Insert fuel injector to be tested into measuring container from VAG1602 fuel analyzer. (Scheme 57): Inserting Fuel Injector To Be Tested Into Measuring Container From VAG1602 Fuel Analyzer
3. Switch ignition on.

Using adapter cables from VAG1594 connector test kit

1. Connect jumper wire between test box terminals D11 and A4 (to activate fuel pump relay).
2. Connect jumper wire between test box terminals A2 and E7 (to activate Motronic ECM power supply relay and supply voltage to fuel injectors).
3. Connect harness connector for cylinder 1 fuel injector to fuel injector being tested on right cylinder bank (bank 1).

To check fuel injectors for right cylinder bank (bank 1)

1. Temporarily connect jumper wire between test box terminals E11 (Ground) and terminal E1, for 30 seconds. Specified value: 105-115 ml (3.5-3.8 oz.)
2. Connect harness connector for cylinder 5 fuel injector to fuel injector being tested on left cylinder bank (bank 2).

To check fuel injectors for left cylinder bank (bank 2)

1. Temporarily connect jumper wire between test box terminal E11 (Ground) and terminal E5, for 30 seconds. Specified value: 105-115 ml (3.5-3.8 oz.)
2. Switch ignition off.

If fuel delivery is not OK

1. Switch off fuel pump and Motronic ECM power supply relay (disconnect jumpered connections at test box).
2. Replace faulty fuel injector(s).
3. Install fuel rail. See «INSTALLING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__installing) .
4. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .
5. If fuel delivery for all fuel injectors is not OK
6. Check fuel pressure. See «FUEL PRESSURE REGULATOR AND RESIDUAL FUEL PRESSURE, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__fuel-pressure-regulator-and-residual-fuel) .

Note. When checking fuel injector delivery volume, also check injector spray pattern. The spray pattern must be the same for all 8 fuel injectors.

Installing

Installation of the fuel rail and the fuel injectors is the reverse of removal. Also observe the following special points

1. Replace all O-rings at all connections that have been opened. To replace the front O-ring, do not remove the plastic cap from the valve head. Slip the O-ring over the plastic cap.
2. Lubricate O-rings with clean engine oil.
3. Install fuel injectors upright to stop (open connectors must face outward) and secure injectors with retaining clips.
4. Place fuel rail with installed fuel injectors into position at intake manifold and press in to stop.
5. Insert bolts by hand. Lightly push fuel rail by hand toward intake manifold and tighten bolts to 10 Nm (7 ft lb).
6. Check fuel injectors for correct installation position (open electrical connectors face outward).
7. Check to see that fuel injector retaining clamps are properly seated.

Scheme 57

1. Disconnect harness connector for fuel injector to be tested.
2. Using multimeter US 1119 (Fluke 83 or equivalent), check resistance between fuel injector terminals. Specified value: 12-20 ohm
3. If resistance is not OK, replace faulty fuel injector. (Scheme 58): Checking Resistance Between Fuel Injector Terminals

Scheme 58

1. Disconnect harness connector for fuel injector to be tested.
2. Connect VAG1527B LED voltage tester between fuel injector connector terminal 1 and engine Ground. (Scheme 59): Identifying Fuel Injector Harness Connector Terminals
3. Switch ignition on. LED must light up.
4. If LED does not light, check wiring for open circuit between terminal 1, fuse for fuel injectors (at E-box in plenum), and power supply relay.
5. If LED does light, check actuation of fuel injectors.

Scheme 59

Scheme 60

Scheme 61

1. Disconnect harness connector for fuel injector to be tested.
2. Connect VAG1527B LED voltage tester between terminals 1 and 2, using adapter cables from VAG1594 connector test kit. (Scheme 60): Identifying Fuel Injector Harness Connector Terminals Initiate output Diagnostic Test Mode (DTM) and actuate fuel injectors. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan). (Scheme 61): VAG15278 Tool Display - Output Diagnostic Test Mode (Injector, Cyl. 1) NOTE: Output signals are checked by listening for the sound of the fuel injector being actuated, or checking by feel for mechanical evidence of actuation (clicking, vibration, etc.).
3. Begin test by partially opening throttle (closed throttle position switch open). see scheme 28: Partially Opening Throttle Fuel injector will be heard and felt to click 5 times.
4. All remaining fuel injectors are checked in sequence by pressing -->button on VAG1551 scan tool.
5. Using this method, check all fuel injectors. LED must light up each time.

If LED does not light

1. Connect VAG1598/19 test box to Engine Control Module (ECM) wiring harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Check wiring harness for continuity or short circuit to positive (B+) between each fuel injector harness connector terminal 2 and corresponding ECM/test box socket: FUEL INJECTOR CIRCUIT TEST: ACTUATION Fuel injector connector (terminal 2) VAG1598/19 test box socket Cyl. 1 E1 Cyl. 2 D7 Cyl. 3 D6 Cyl. 4 E2 Cyl. 5 E5 Cyl. 6 D2 Cyl. 7 D3 Cyl. 8 E6
3. Repair open circuit or short circuit as necessary.

Identifying ECM Connectors And Terminals. Scheme 62

If voltage supply and fuel injector actuation are OK

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) .
2. Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Fuel pump relay, checking

Note. The fuel pump relay is located on the central electrical panel in the right-side footwell, in relay position 6.

1. Remove fuel pump relay -J17-. Relay is located on central electrical panel in right-side footwell (mounted on fuse panel). see scheme 30: Locating Fuel Pump Relay J17 (Position No. 6)
2. Switch ignition on.
3. Connect multimeter US 1119 (Fluke 83 or equivalent) and check for voltage between relay terminals: 28 (B+, terminal 15) and 34 (Ground) 32 (B+, terminal 30) and 34 (Ground). Specified value: approx. Battery Positive Voltage (B+)

Identifying Fuel Pump Relay Terminals. Scheme 63

If voltage is not OK

1. Check wiring for open circuit.

1. Connect VAG1527B LED voltage tester between relay terminals 28 (B+) and 29 (Ground from ECM). see scheme 32: Identifying Fuel Pump Relay Terminals
2. LED must light up for approx. 1 second and then go out. When operating starter, LED must light up continuously. NOTE: LED voltage testers with little current draw do not completely go out after 1 second, but will continue to glow dimly until the starter motor is operated.

If LED does not light up, check wiring as follows

1. Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and check for continuity between relay terminal 29 and test box socket A4.
3. If there is no continuity
4. Check wiring for open or short circuit.

Identifying Connectors Of ECM. Scheme 64

If there is no open circuit, and LED does not light up

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) . Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

If wiring harness and actuation of fuel pump relay are OK

1. Replace fuel pump relay.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Checking function of fuel pump relay -J17

1. Remove cover for fuse panel on right-side A-pillar.
2. Connect VAG1527B LED voltage tester between upper terminal for fuse 1 or fuse 3 (located at blue fuse holder, fourth row from top) and Ground.
3. Operate starter motor for a few seconds. Fuel pump relay should be actuated LED should light up

If LED does not light up, but fuel pump relay is actuated

1. Repeat test using lower fuse terminals.

If LED still does not light up

1. Remove fuel pump relay from central electrical panel in right-side footwell, relay position 6.
2. Check wiring for open circuit between: Relay panel terminal 30 (relay position 6) and fuse 1 Fuse 3 and relay panel terminal 31 (Ground)

Identifying Fuel Pump Relay Terminals. Scheme 65

If there is no open circuit

1. Replace fuel pump relay.

If fuel pump relay was not actuated

1. Check relay actuation circuit. See «CHECKING FUEL PUMP RELAY ACTUATION»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .

If voltage supply and relay actuation circuit are OK

1. Replace fuel pump relay.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Oxygen Sensor (O2S) control, checking

Note. The oxygen sensor compares the oxygen content of the outside air with the residual oxygen content in the exhaust gas, and generates a voltage input signal to the Engine Control Module (ECM). The voltage signal for a "rich" mixture (little residual oxygen content) is approx. 0.7-0.9 volts. The voltage signal for a "lean" mixture (high residual oxygen content) is approx. 0-0.2 volts. Because oxygen sensors are insulated from engine ground, negative current flow may occur. During the transition from "rich" to "lean" mixture (Lambda = 1.0), voltage fluctuates between 0.7-0.9 volts and 0-0.2 volts, and vice versa. Because of the abrupt voltage changes, the ECM cannot continuously maintain the ideal fuel/air mixture (Lambda = 1.0). Oxygen sensor control is continuously changing between conditions that are slightly too lean and slightly too rich.

Note. If oxygen sensor voltage does not fluctuate, the sensor does not respond, or responds too slowly, the following causes are possible: Slits in the oxygen sensor tip are plugged Sensor not up to operating temperature (cold-start) Sensor has been thermally overloaded Transition resistance in signal wire or reference Ground connection Sensor has been damaged by electrical contact cleaner or similar contaminant (drawn through signal wire by capillary action due to thermal fluctuation). Sensor has been damaged by exposure to silicone. When using silicone sprays and sealants, silicone residue is drawn into the engine where it passes unburned into the exhaust and can damage the oxygen sensor.

1. HO2S properly installed
2. Exhaust system free of leaks

Checking

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Heated Oxygen Sensor (HO2S) (1 Of 5). Scheme 66

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Heated Oxygen Sensor (HO2S) (2 Of 5). Scheme 67

1. Press buttons -0-, -0- and -3- to input display group number 3 (003), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Heated Oxygen Sensor (HO2S) (3 Of 5). Scheme 68

1. Check specified values for basic functions at engine idle speed (display field 3): see scheme 39: Display Group 3: Engine Idle Speed Continue checking only after engine coolant temperature in display field 3 has reached at least 85°C (185°F).
2. Press -C- button.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Heated Oxygen Sensor (HO2S) (4 Of 5). Scheme 69

1. Press buttons -0-, -2- and -6- to input display group number 26 (026), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Heated Oxygen Sensor (HO2S) (5 Of 5). Scheme 70

1. Check specified values for Heated Oxygen Sensors (HO2S and HO2S 2), display fields 1-4: see scheme 42: Display Group 26: Heated Oxygen Sensors (HO2S & HO2S 2) If O2S voltage is constant at 450 mV, go to «OXYGEN SENSOR (O2S) HEATING, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-heating-checking). If B1-S1 OFF or B2-S1 OFF is displayed, check O2S heating. Go to «OXYGEN SENSOR (O2S) HEATING, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-heating-checking). To check O2S wiring and connections, go to «HEATED OXYGEN SENSOR (HO2S) SIGNAL WIRING AND WIRING CONNECTIONS, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__heated-oxygen-sensor-ho2s-signal-wiring).
2. Press -C- button.

Heated Oxygen Sensor (HO2S) signal wiring and wiring connections, checking

Component locations. See COMPONENT LOCATIONS, OVERVIEW .

Note. Heated oxygen sensor signals are monitored by the On Board Diagnostic (OBD) system.

1. Check Diagnostic Trouble Code (DTC) memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) .

If HO2S malfunctions are indicated but O2S heating is OK

1. Disconnect oxygen sensor.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) at 2 VDC measuring range, and check voltage between harness connector terminals 3 and 4.
3. Switch ignition on. Specified value: 450 +/- 50 mV (before TWC)

If voltage is not OK

1. Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Check wiring connections for open circuit, short circuit to B+, and short circuit to Ground: NOTE: Heated Oxygen Sensor (HO2S) -G39- (bank 1) Heated Oxygen Sensor (HO2S) 2 -G108- (bank 2) HO2S G39 OR HO2S 2 G108 CIRCUIT TEST: HO2S or HO2S 2 connector terminal VAG1598/19 test box socket (ECM terminal) 3 (G39) B20 4 (G39) B24 3 (G108) B21 4 (G108) B23

If wiring is OK

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). see scheme 44: Identifying ECM Connectors

1. HO2S properly installed
2. Exhaust system free of leaks

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (1 Of 5). Scheme 71

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (2 Of 5). Scheme 72

1. Press buttons -0-, -0- and -3- to input display group number 3 (003), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (3 Of 5). Scheme 73

1. Check specified values for basic functions at engine idle speed (display field 3): (Scheme 76): Display Group 3: Basic Functions, Engine Idle Speed Continue checking only after engine coolant temperature in display field 3 has reached at least 85°C (185°F).
2. Press -C- button.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (4 Of 5). Scheme 74

1. Press buttons -0-, -2- and -7- to input display group number 27 (027), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Checking Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (5 Of 5). Scheme 75

Scheme 76

1. Check specified values for Oxygen Sensors (O2S and O2S 2) behind Three Way Catalytic Converters (TWC), display fields 1-4: see scheme 51: Display Group 27: Oxygen Sensors Behind Three Way Catalytic Converter If B1-S2 n. OK or B2-S2 n. OK are displayed, check O2S heating. See «OXYGEN SENSOR (O2S) HEATING, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-heating-checking). To check wiring and connections for O2S signal, see «OXYGEN SENSOR (O2S) BEHIND THREE WAY CATALYTIC CONVERTER (TWC) SIGNAL WIRING AND WIRING CONNECTIONS, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__oxygen-sensor-o2s-behind-three-way).
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) signal wiring and wiring connections, checking

Component locations, see COMPONENT LOCATIONS, OVERVIEW .

Note. Heated oxygen sensor signals are monitored by the On Board Diagnostic (OBD) system.

1. Check Diagnostic Trouble Code (DTC) memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) .

If O2S malfunctions are indicated but O2S heating is OK

1. Disconnect oxygen sensor.
2. Connect multimeter US 1119 (Fluke 83 or equivalent), set to 2 VDC measuring range, and check voltage between harness connector terminals 3 and 4.
3. Switch ignition on. Specified value: 450 +/- 50 mV (behind TWC)

If voltage is not OK

1. Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring connections for open circuit, short circuit to B+, and short circuit to Ground: NOTE: Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- (bank 1) Oxygen Sensor (O2S) 2 behind Three Way Catalytic Converter (TWC) -G131- (bank 2) O2S BEHIND TWC CIRCUIT TEST O2S behind TWC connector terminal VAG1598/19 test box socket (ECM terminal) 3 (G130) C17 4 (G130) C21 3 (G131) C18 4 (G131) C20
3. If wiring is OK, replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). see scheme 53: Identifying ECM Connectors

Oxygen Sensor (O2S) heating, checking

For location of harness connectors for HO2S and HO2S 2 (banks 1 and 2), see COMPONENT LOCATIONS, OVERVIEW .

Location of harness connector for O2S behind TWC (bank 1): under right front carpet.

Locating Harness Connector For O2S Behind TWC (Bank 1) Under Right Front Carpet. Scheme 77

Location of harness connector for O2S 2 behind TWC (bank 2): under left front carpet.

Note. Heated oxygen sensor signals are monitored by the On Board Diagnostic (OBD) system.

Locating Harness Connector For O2S 2 Behind TWC (Bank 2) Under Left Front Carpet. Scheme 78

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Oxygen Sensor Heating, Checking (1 Of 3). Scheme 79

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 Or VAG1552 Scan Tool Display - Oxygen Sensor Heating, Checking (2 Of 3). Scheme 80

1. Press buttons -0-, -2- and -8- to input display group number 28 (028), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Oxygen sensor Heating, Checking (3 Of 3). Scheme 81

1. Check specified values for O2S heating (display fields 1-4): (Scheme 84): Display Group 28: Oxygen Sensor (O2S) Heating If ohms displayed value is outside of specified range, continue with test procedure.
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

If O2S heating circuit malfunction is indicated

1. Disconnect oxygen sensor harness connector.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and check for continuity (resistance) between harness connector terminals 1 and 2. Specified value at room temperature: 2-10 ohm (Scheme 85): Identifying Oxygen Sensor Connector Terminals NOTE: Wire resistance increases significantly at higher temperatures.

If there is an open circuit

1. Replace oxygen sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

If there is continuity

1. Check O2S heater circuit as follows.
2. Check oxygen sensor fuses 3 and 4 at blue fuse panel located on right-side A-pillar.

If fuses are OK

1. Connect VAG1527B LED voltage tester between oxygen sensor harness connector terminal 1 and engine Ground.
2. Briefly operate starter. (Do not operate starter for more than 2 minutes, to avoid storing malfunction in DTC memory) LED must light up.

Identifying Oxygen Sensor Harness Connector Terminals. Scheme 82

If LED does not light

1. Check wiring for open or short circuit between oxygen sensor harness connector terminal 1 and fuel pump relay.

If wiring and fuses are OK, but LED still does not light up

Identifying Oxygen Sensor Harness Connector Terminals. Scheme 83

If voltage supply is OK

Scheme 84

Scheme 85

1. Check wiring for open or short circuits: Heated Oxygen Sensor (HO2S) -G39- Oxygen Sensor (O2S) heater -Z19- Heated Oxygen Sensor (HO2S) 2 -G108- Oxygen Sensor (O2S) 2 heater -Z28- HO2S Z19 OR HO2S 2 Z28: HEATER CIRCUIT TEST HO2S or HO2S 2 connector terminal VAG1598/19 test box socket (ECM terminal) 2 (O2S heater -Z19-) E10 2 (O2S 2 heater - Z28-) E9 see scheme 63: Identifying Oxygen Sensor Harness Connector Terminals
2. Check wiring for open or short circuits: Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- Oxygen Sensor (O2S) heater -Z29- Oxygen Sensor (O2S) 2 behind Three Way Catalytic Converter (TWC) -G131- Oxygen Sensor (O2S) 2 heater -Z30- O2S Z29 & Z30 BEHIND TWC: HEATER CIRCUIT TEST O2S behind TWC connector terminal VAG1598/19 test box socket (ECM terminal) 2 (O2S heater -Z29-) E4 2 (O2S 2 heater - Z30-) E8 see scheme 64: Identifying Oxygen Sensor Harness Connector Terminals
3. If there are no open or short circuits, replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). (Scheme 89): Identifying ECM Connectors

Heated Oxygen Sensor (HO2S) aging, checking

Test conditions

1. Engine coolant temperature at least 85°C (185°F)

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Heated Oxygen Sensor Aging, Checking (1 Of 5). Scheme 86

1. Press buttons -0- and -4- to select "Basic Setting" function 04, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Heated Oxygen Sensor Aging, Checking (2 Of 5). Scheme 87

1. Press buttons -0-, -2- and -9- to input display group number 29 (029), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Heated Oxygen Sensor Aging, Checking (3 Of 5). Scheme 88

Note. To keep the exhaust gas and the three way catalytic converter at the proper temperature, hold engine speed within the specified RPM range for at least 1 minute. Note the status of the oxygen sensor control function in display field 4.

Scheme 89

1. Check specified values for Heated Oxygen Sensor (HO2S) aging (bank 1), display fields 2 and 4. (Scheme 92) (Scheme 92): Display Group 29: Heated Oxygen Sensor Aging (Bank 1) If specified values in (Scheme 92) are not displayed, go to «IF SPECIFIED VALUES ARE NOT DISPLAYED»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__if-specified-values-are-not-displayed). Three Way Catalytic Converter (TWC) temperature greater than 300°C (display field 2)
2. Raise engine speed to 1800-2200 RPM, and hold (display field 1).
3. Hold engine speed in this range until specified HO2S status is achieved (display field 4). After initiating diagnostic test, value in display field 4 must switch from "Test OFF" to "Test ON." Specified value after completed test: B1-S1 OK
4. Press -3- button to advance to display group 30 (030).
5. Check specified values for Heated Oxygen Sensor (HO2S) 2 aging (bank 2), display fields 2-4. see scheme 70 see scheme 70: Display Group 30: Heated Oxygen Sensor Aging (Bank 2) If specified values in see scheme 70 are not displayed, go to «IF SPECIFIED VALUES ARE NOT DISPLAYED»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__if-specified-values-are-not-displayed). Three Way Catalytic Converter (TWC) temperature greater than 300°C (display field 2)
6. Raise engine speed to 1800-2200 RPM, and hold (display field 1).
7. Hold engine speed in this range until specified HO2S 2 status is achieved (display field 4). After initiating diagnostic test, value in display field 4 must switch from "Test OFF" to "Test ON." Specified value after completed test: B2-S1 OK
8. Press -8- button to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.
9. Press -C- button.

Indicated on display

VAG1552 Scan Tool Display - Heated Oxygen Sensor Aging, Checking (4 Of 5). Scheme 90

1. Press buttons -0-, -2- and -5- to input display group number 25 (025), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Heated Oxygen Sensor Aging, Checking (5 Of 5). Scheme 91

Scheme 92

1. Check specified values for Oxygen Sensor (O2S) control for Oxygen Sensors (O2S) behind Three Way Catalytic Converters (TWC), banks 1 and 2 (display fields 1-4). (Scheme 96) (Scheme 96): Display Group 25: Oxygen Sensor Control (Banks 1 & 2)
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

If specified values are not displayed

1. Replace oxygen sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Heated Oxygen Sensor (HO2S), removing and installing

See COMPONENT LOCATIONS, OVERVIEW .

Note. Use special tool VAG3337/9 for removal and installation. Cable ties and other retainers must be reinstalled in the same locations to avoid damage due to HO2S wire coming in contact with exhaust system. Tightening torque: 50 Nm (37 ft lb) The HO2S threads are coated with a thread sealing compound that must not come in contact with the slits in the sensor tip.

IAC function, checking

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Idle Air Control, Checking (1 Of 5). Scheme 93

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Idle Air Control, Checking (2 Of 5). Scheme 94

1. Press buttons -0-, -0- and -4- to input display group number 4 (004), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Idle Air Control, Checking (3 Of 5). Scheme 95

Scheme 96

1. Check specified values for basic functions at engine idle speed (display field 4). (Scheme 99) (Scheme 99): Display Group 4: Basic Functions, Engine Idle Speed
2. Press -C- button.

Indicated on display

VAG1552 Scan Tool Display - Idle Air Control, Checking (4 Of 5). Scheme 97

1. Press buttons -0-, -0- and -6- to input display group number 6 (006), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Idle Air Control, Checking (5 Of 5). Scheme 98

Scheme 99

1. Check specified values for idle air control at engine idle speed (display fields Page 1-4.). (Scheme 100) (Scheme 100): Display Group 6: Idle Air Control (IAC)
2. Press button -3- to advance to display group 7.
3. Check specified values for idle air control at engine idle speed (display fields Page 1-4.). see scheme 81 see scheme 81: Display Group 7: Idle Air Control (IAC) To check IAC valve functions, see «IDLE AIR CONTROL (IAC) VALVE, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz). Note on display field 3: Increased temperature of the coil in the Idle Air Control (IAC) valve changes the internal resistance. Idle air control, and the opening of the IAC valve that is calculated by the Engine Control Module (ECM), requires a precise voltage signal. If this voltage is reduced because of increased coil resistance due to heat, the IAC valve duty cycle has to be changed until the calculated voltage is reached. With the engine cold (room temperature) the control factor is approx. 1.0. As the coil heats up the duty cycle increases. Values above 1.2 indicate resistance in the wiring between the ECM and the IAC valve. Note on display field 4: The voltage required to maintain the necessary air flow through the IAC valve is calculated by the ECM. If the air flow through the valve is too low (e.g. due to increased air resistance) the IAC valve must be opened farther to compensate. This deviation is recognized by the ECM, which compensates by applying a different control factor (learning process). Values that deviate significantly indicate air flow restrictions or sticking of the IAC valve.
4. Press --> button to advance program sequence.
5. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

1. Remove IAC valve -N71- from mounting on engine (do not disconnect harness connector).
2. Visually inspect rotary valve for scuff marks (arrow). CAUTION: Do not use a screwdriver or other tools to check the valve for ease of movement. see scheme 82: Inspecting Rotary Valve For Scuff Marks
3. Initiate output Diagnostic Test Mode (DTM); and check actuation of IAC valve. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan).
4. Check that rotary slide moves freely between fully open and fully closed positions.

If there are scuff marks or other malfunctions that restrict free movement of rotary slide

1. Replace IAC valve.
2. Check Diagnostic Trouble Code (DTC) memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) .
3. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If valve does not respond
4. Check idle air control signal from ECM. See «CHECKING IDLE AIR CONTROL SIGNAL FROM ECM»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__checking-idle-air-control-signal-from) .

1. Check IAC valve -N71- mechanical function.
2. Disconnect harness connector from valve.
3. Connect multimeter US 1119 (Fluke 83 or equivalent) and check resistance across terminals on IAC valve. see scheme 83: Checking Resistance Across Terminals On IAC Valve

Specified value: 7.0-11.0 ohm

Note. At room temperature the resistance is in the lower part of the specified range. At operating temperature the resistance is in the upper part of the range.

If resistance is outside specified range

1. Replace IAC valve -N71-.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Checking idle air control signal from ECM

1. Disconnect wiring harness connector from IAC valve -N71- and connect VAG1527B LED voltage tester across connector terminals 1 and 2.
2. Initiate output Diagnostic Test Mode (DTM) and check IAC valve. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan) . LED must flash.

Note. The LED does not go completely out, but becomes brighter and dimmer. The output Diagnostic Test Mode (DTM) signal for the IAC valve is interrupted after one minute. To repeat the test, briefly switch the ignition off and start the output DTM again.

If LED does not flash

Scheme 100

1. Connect VAG 1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring for open circuit or short circuit between IAC valve and ECM/test box. IAC VALVE CIRCUIT TEST: OPENS/SHORTS IAC valve connector terminal VAG1598/19 test box socket (ECM terminal) 1 D5 2 D1 If wiring is OK and there is no signal: (Scheme 105): Identifying Connectors On ECM

Closed Throttle Position (CTP) switch, checking

The CTP switch is located at the rear of the throttle body, at the Throttle Position (TP) sensor.

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 Scan Tool Display - Closed Throttle Position Switch, Checking (1 Of 3). Scheme 101

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 Scan Tool Display - Closed Throttle Position Switch, Checking (2 Of 3). Scheme 102

1. Press buttons -0-, -0- and -4- to input display group number 4 (004), and press -Q- button to confirm input.

Indicated on display

VAG1551 Scan Tool Display - Closed Throttle Position Switch, Checking (3 Of 3). Scheme 103

Scheme 104

1. Check specified values for basic functions at engine idle speed (display field 4). (Scheme 106) (Scheme 106): Display Group 4: Basic Functions, Engine Idle Speed Specified value in display field 4: "Idle"

If display does not change as described

1. Adjust accelerator pedal cable or linkage for cruise control. See «ACCELERATOR PEDAL CABLE, ADJUSTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#fuel-supply-37l-42l-v8-4v-aew-abz__accelerator-pedal-cable-adjusting) .
2. Check Throttle Position (TP) sensor for contamination.

If "Part throt" is displayed only after longer accelerator pedal travel

1. Briefly touch accelerator pedal (only a few millimeters). Specified value: "Part throt"

If accelerator pedal cable adjustment is OK

1. Check CTP switch and wiring.

Scheme 105

1. Remove throttle body to adjust CTP switch. NOTE: When adjusting the CTP switch, the Throttle Position (TP) sensor is adjusted at the same time.
2. Loosen both CTP switch mounting screws.
3. Rotate CTP switch in direction shown (arrow) until reaching stop. While doing so, do not depress accelerator pedal.
4. Tighten CTP switch in this position. (Scheme 107): Rotating CTP Switch In Direction Shown (Arrow) Until Reaching Stop

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 test box, connecting»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Disconnect harness connector from Throttle Position (TP) sensor.
3. Check wiring for continuity or short circuit: TP SENSOR CIRCUIT TEST: SHORT CIRCUIT TP sensor connector terminal VAG1598/19 test box socket (ECM terminal) 4 (Ground) D11 (Ground) 6 B4 see scheme 91: Identifying Throttle Position (TP) Sensor Harness Connector Terminals
4. Repair wiring to correct open or short circuit as necessary. NOTE: When repairing terminals in TP sensor connector, be sure to use only gold-plated terminals. see scheme 92: Identifying ECM Connectors

If wiring is OK

1. Check CTP switch.
2. Reconnect TP sensor harness connector.
3. Connect multimeter US 1119 (Fluke 83 or equivalent) and check for continuity between terminals D11 and B4. Specified value: continuity when throttle valve is closed
4. Open throttle valve Specified value: no continuity

If results are not as specified

1. Replace Throttle Position (TP) sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

1. Switch ignition on. Initiate output Diagnostic Test Mode (DTM) and check actuation of intake manifold change-over valve -N156-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan). see scheme 93: Checking Actuation Of Intake Manifold Change-Over Valve

The valve should click (confirm by sound and touch). After one minute, the output DTM will be interrupted.

If valve does not click

Scheme 106

1. Switch ignition off.
2. Disconnect harness connector from IMT valve.
3. Connect multimeter US 1119 (Fluke 83 or equivalent) and measure resistance across IMT valve terminals. Specified value: 25-35 ohms see scheme 94: Measuring Resistance Across IMT Valve Terminals

If resistance is not OK

1. Replace intake manifold IMT valve.

If resistance is OK

Scheme 107

1. Connect VAG1527B LED voltage tester between harness connector terminal 1 and Ground, using adapter cables from VAG1594 connector test kit.
2. Switch ignition on. LED must light up. (Scheme 112): Identifying IMT Valve Harness Connector Terminals

If LED does not light up

1. Check fuse for intake manifold IMT valve in electronics box (E-box) in plenum.

If fuse is OK

1. Check wiring for open or short circuit between IMT valve harness connector terminal 1 and fuse in E-box.

If wiring (voltage supply) is OK

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Check wiring for open or short circuit between IMT valve harness connector terminal 2 and ECM/test box socket A5.

Identifying ECM Harness Connectors. Scheme 108

If wiring is OK

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) . Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .
2. Check intake manifold IMT valve function. See «INTAKE MANIFOLD TUNING (IMT) VALVE FUNCTION, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__intake-manifold-tuning-imt-valve-function) .

Intake Manifold Tuning (IMT) valve function, checking

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Intake Manifold Tuning Valve Function (1 Of 4). Scheme 109

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Intake Manifold Tuning Valve Function (2 Of 4). Scheme 110

1. Press buttons -0-, -2- and -2- to input display group number 22 (022), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Intake Manifold Tuning Valve Function (3 Of 4). Scheme 111

Scheme 112

1. Check specified values for IMT valve function (display fields 1 and 4). see scheme 100 see scheme 100: Display Group 22: Intake Manifold Tuning (IMT) Valve
2. Check display field 4. Specified value: "SU-V OFF"
3. Raise engine speed to approx. 4200 RPM and hold (display field 1) and check operating condition in display field 4. Specified value: "SU-V ON" At the same time, the valve must cycle (change over) one time. If "SU-V ON" is displayed but the change-over does not occur: Check pneumatic function of IMT valve. See «INTAKE MANIFOLD TUNING (IMT) VALVE PNEUMATIC FUNCTION, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz).

1. Disconnect vacuum hose from intake manifold.
2. Connect hand vacuum pump VAG1390 to disconnected vacuum hose. (Scheme 116): Using Hand Vacuum Pump To Check IMT Valve
3. Operate hand pump at least 50 strokes (build-up of vacuum must be noticeable).
4. Disconnect vacuum hose from hand pump. The vacuum must be maintained at the IMT valve (decrease between hand pump and check valve only). If a release of vacuum can be heard, the check valve is leaking (replace check valve).
5. Initiate output Diagnostic Test Mode (DTM) and check actuation of intake manifold change-over (IMT) valve -N156-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan). (Scheme 117): VAG 1552 Scan Tool Display - Output Diagnostic Test Mode, IMT Valve The valve should click (confirm by sound and touch). The change-over should occur (approx.. times), but stop when there is no longer vacuum in the reservoir. With no vacuum, the valve will only click. After one minute the DTM will be interrupted.

If no change-over occurs, the following are possible malfunctions

1. Intake manifold change-over mechanism sticking (try moving it by hand).
2. Vacuum system leaking (hose connections, lines, reservoir or vacuum unit).
3. Check valve (black/white) leaking, plugged or incorrectly installed.
4. IMT valve faulty (plugged, or otherwise does not operate). NOTE: The vacuum reservoir is located under the left-front fender, near the A-pillar.

Function, checking

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Evaporative Emissions (EVAP) System (1 Of 3). Scheme 113

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Evaporative Emissions (EVAP) System (2 Of 3). Scheme 114

1. Press buttons -0-, -1- and -2- to input display group number 12 (012), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Evaporative Emissions (EVAP) System (3 Of 3). Scheme 115

Scheme 116

1. Check specified values for function of EVAP system at idle (display fields Page 1-4.). (Scheme 119) (Scheme 119): Display Group 12: Evaporative Emissions (EVAP) System At Idle Check display field 4: EVAP SYSTEM OPERATIONAL "EVAPactive" = EVAP system operational "EVAPinact." = engine cold "lambda-Adaptation" = no EVAP system operation, oxygen sensor control learning Check display field 2: EVAP SYSTEM LEAKING -5% = EVAP system leaking, or no fuel vapors in EVAP canister 95% = EVAP canister saturated 100% = EVAP system blocked
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Scheme 117

1. Disconnect harness connector from EVAP canister purge regulator valve -N80-.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and measure resistance across valve terminals. Specified value: 20-35 ohms see scheme 107: Checking EVAP Canister Purge Regulator Valve Resistance

If resistance is not OK

1. Replace EVAP canister purge regulator valve.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Checking voltage supply

1. Fuse for EVAP canister purge regulator valve -N80- OK (located in E-box in plenum)

1. Disconnect harness connector from EVAP canister purge regulator valve -N80-.
2. Connect VAG1527B LED voltage tester between connector terminal 1 and Ground. see scheme 108: Identifying EVAP Canister Purge Regulator Valve Harness Connector Terminals
3. Switch ignition on. LED must light up.

If LED does not light

1. Check wiring between connector terminal 1 and fuse for EVAP canister purge regulator valve -N80- (E-box in plenum).

If wiring is OK

1. Check Motronic ECM power supply relay. See «ENGINE CONTROL MODULE (ECM) INPUT SIGNALS, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .

1. Connect VAG1527B LED voltage tester between harness connector terminals 1 (B+) and 2. see scheme 109: Identifying EVAP Canister Purge Regulator Valve Harness Connector Terminals
2. Initiate output Diagnostic Test Mode (DTM) and check actuation of EVAP canister purge regulator valve -N80-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__output-diagnostic-test-mode-dtm-scan). LED must flash

If LED does not light, or lights continuously

1. Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring between EVAP canister purge regulator valve connector terminal 2 and ECM/test box socket A8, and repair as necessary. (Scheme 123): Identifying ECM Connectors

If EVAP components and wiring are OK

1. Check EVAP hoses and connections for leaks or blockage.

If EVAP hoses and lines are OK, and properly connected

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) .
2. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Electrical check

1. Disconnect harness connector for Leak Detection Pump (LDP) -V144-.
2. Connect multimeter US1119 (Fluke 83 or equivalent) between terminals -1- and -3- of LDP and check resistance. Specified value: 640-720 ohms
3. Connect multimeter US1119 (Fluke 83 or equivalent) between terminals -2- and -3- of LDP and check resistance. Specified value: 17.5-27.5 ohms

Identifying Leak Detection Pump Connector Terminals. Scheme 118

If resistance is not OK

1. Replace leak detection pump.

Scheme 119

1. Disconnect harness connector for LDP -V144-.
2. Connect VAG1527B LED voltage tester between connector terminal -3- (B+) and engine Ground (GND). (Scheme 124): Identifying Leak Detection Pump Harness Connector Terminals
3. Start engine and let idle. LED must light up.

If LED does not light

1. Check fuse for LDP -V144-.
2. Check wiring for open circuit between terminal -3- and fuse, according to wiring diagram. Specified value: max. 0.5 ohm
3. Check fuel pump relay. See «FUEL PUMP RELAY, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__fuel-pump-relay-checking) .

Test requirement

1. Engine coolant temperature at least 85°C (185°F)

1. Connect VAG1551 or VAG1552 Scan Tool (ST), and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Checking Air Control Valve For Fuel Injectors (1 Of 3). Scheme 120

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Checking Air Control Valve For Fuel Injectors (2 Of 3). Scheme 121

1. Press buttons -0-, -3- and -5- to input display group number 35 (035), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Checking Air Control Valve For Fuel Injectors (3 Of 3). Scheme 122

Scheme 123

1. Check specified values for air control valve for fuel injectors (air-shrouded fuel injectors), display field 4. (Scheme 125) (Scheme 125): Display Group 35: Air Control Valve For Fuel Injectors Specified value in display field 4: A-IV OK

If display is not as specified

1. Press -4- button on VAG1551 scan tool to select "Basic Setting" function 04.
2. Check specified values for air control valve for fuel injectors (air-shrouded fuel injectors), display fields 2 and 4. (Scheme 126) (Scheme 126): Display Group 35: Air Control Valve For Fuel Injectors

If display is not as specified

1. Check air lines for blockage.
2. Check air control valve for fuel injectors. See «AIR CONTROL VALVE FOR FUEL INJECTORS, ELECTRICAL TESTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .
3. Press -->button to advance program sequence.
4. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Scheme 124

1. Disconnect harness connector from air control valve for fuel injectors -N212-.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and check resistance across valve terminals. Specified value: 15-35 ohms (Scheme 127): Checking Air Control Valve For Fuel Injectors Resistance

If resistance is not OK

1. Replace air control valve for fuel injectors -N212-.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

1. Fuse for air control valve for fuel injectors -N212- OK (E-box in plenum)

1. Disconnect harness connector from air control valve for fuel injectors -N212-.
2. Connect VAG1527B LED voltage tester between connector terminal 1 and Ground.
3. Switch ignition on. LED must light up see scheme 119: Identifying Air Control Valve For Fuel Injectors Harness Connector Terminals

If LED does not light

1. Check wiring for open circuit between connector terminal 1, fuse for air control valve for fuel injectors -N212- (E-box in plenum), and Motronic ECM power supply relay.

If wiring is OK

1. Check Motronic ECM power supply relay. See «ENGINE CONTROL MODULE (ECM) INPUT SIGNALS, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .

Checking actuation

1. Connect VAG1527B LED voltage tester between harness connector terminals 1 (B+) and 2 (harness connector for air control valve remains connected).
2. Start engine. LED must light up. NOTE: When engine is cold, the LED will light up at idle. When engine is at normal operating temperature, LED lights up only above approx. 1500 RPM.

If LED does not light up

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring between air control valve connector terminal 2 and ECM/test box socket D4. see scheme 120: Identifying ECM Terminal Connectors
3. Check air hoses and lines (for air-shrouded fuel injectors) for leaks and blockage.

If air control valve, wiring, air hoses and lines are OK

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) . Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Motronic ECM power supply relay, checking

The Motronic ECM power supply relay -J271- is located in the electronics box (E-box) in the plenum.

The relay supplies power to the following components

1. Fuel injectors
2. Motronic Engine Control Module (ECM) -J220
3. EVAP canister purge regulator valve -N80
4. Intake manifold change-over valve -N156
5. Air control valve for fuel injectors -N212

1. Remove Motronic ECM power supply relay -J271- from relay position 1 (E-box in plenum).
2. Connect VAG1527B LED voltage tester between relay socket terminal 2 (B+, terminal 30) and engine Ground.
3. Connect VAG1527B LED voltage tester between relay socket terminal 4 (B+, terminal 30) and engine Ground. LED must light up both times. see scheme 121: Identifying Motronic ECM Power Supply Relay -J271- Terminals

If LED does not light

Scheme 125

1. Check wiring for open circuits.
2. Connect VAG1527B LED voltage tester between relay socket terminals 2 (B+, terminal 30) and 6 (Ground for ECM).
3. Switch ignition on. LED must light up. (Scheme 131): Identifying Motronic ECM Power Supply Relay -J271- Terminals

If LED does not light

Scheme 126

1. Switch ignition off.
2. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
3. Check wiring for open circuits between relay socket terminal 6 and ECM/test box socket A2. (Scheme 132): Identifying ECM Connectors

If there are no open circuits and LED still does not light up

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) . Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .
2. Reinstall Motronic ECM power supply relay.
3. Disconnect test box and reconnect ECM.
4. Switch ignition on.
5. Connect VAG1527B LED voltage tester between engine Ground and upper fuse terminal (fuses for fuel injectors and for EVAP canister purge regulator valve -N80-). LED must light up (both fuses supply voltage to one terminal).

If LED does not light for either fuse

Scheme 127

1. Check wiring for open circuit between fuses and Motronic ECM power supply relay socket terminal 8. (Scheme 133): Identifying Motronic ECM Power Supply Relay -J271- Terminals

If there are no open circuits

1. Replace Motronic ECM power supply relay -J271-.
2. Reinstall fuses and relay.
3. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Throttle Position (TP) sensor, checking and adjusting

The throttle position sensor is located at the back side of the throttle body.

Checking function

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Checking Throttle Position Sensor (1 Of 3). Scheme 128

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Checking Throttle Position Sensor (2 Of 3). Scheme 129

1. Press buttons -0-, -0- and -4- to input display group number 4 (004), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Checking Throttle Position Sensor (3 Of 3). Scheme 130

Scheme 131

1. Check specified values for basic functions with ignition switched on (display field 1). see scheme 128 see scheme 128: Display Group 4: Basic Functions, Ignition On

If throttle angle is not OK

1. Check accelerator pedal cable adjustment. See «ACCELERATOR PEDAL CABLE, ADJUSTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#fuel-supply-37l-42l-v8-4v-aew-abz__accelerator-pedal-cable-adjusting) .
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

If accelerator pedal cable adjustment is OK

1. Check Closed Throttle Position (CTP) switch and adjust as necessary. See «CLOSED THROTTLE POSITION (CTP) SWITCH, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__closed-throttle-position-ctp-switch-checking) . NOTE: When the CTP switch is adjusted, the TP sensor is also adjusted at the same time.

If CTP switch adjustment is OK

1. Check voltage supply for TP sensor.

Scheme 132

1. Disconnect harness connector from TP sensor.
2. Switch ignition on.
3. Connect multimeter US 1119 (Fluke 83 or equivalent) and check voltage between connector terminals 1 and 2, and between terminals 2 and 3. see scheme 129: Identifying TP Sensor Harness Connector Terminals Specified value: 4.5-5.5 volts

If both measurements are outside the specified range

1. Check resistance of TP sensor. See «CHECKING RESISTANCE»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz) .

If just one measurement is outside the specified range, check wiring to ECM as follows

Scheme 133

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting). (Scheme 137): Identifying ECM Connectors
2. Disconnect harness connector from TP sensor. NOTE: When repairing TP sensor connector terminals, use only gold-plated terminals.
3. Check wiring for open or short circuits as follows: (Scheme 138): Identifying TP Sensor Harness Connector Terminals TP SENSOR CIRCUIT TEST: OPENS/SHORTS TP sensor connector terminal VAG1598/19 test box socket (ECM terminal) 1 A3 2 A19 3 A24
4. If wiring is OK
5. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz).

1. Disconnect harness connector from TP sensor.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and check resistance between connector terminals 1 and 2. Specified value: 1.5-2.6 kohm (Scheme 139): Identifying TP Sensor Terminals
3. Check resistance between terminals 2 and 3. Specified value: 0...3 kohm
4. Slowly open throttle valve to Wide Open Throttle (WOT) position. Specified value: 2...6 kohm

If one measured value is outside specified range

1. Replace TP sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Adjusting

The TP sensor is adjusted by adjusting the Closed Throttle Position (CTP) switch.

Adjusting CTP switch. See ADJUSTING .

Mass Air Flow (MAF) sensor, checking

The MAF sensor is located in the upper air cleaner housing.

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Mass Air Flow (MAF) Sensor (1 Of 3). Scheme 134

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Mass Air Flow (MAF) Sensor (2 Of 3). Scheme 135

1. Press buttons -0-, -0- and -7- to input display group number 7 (007), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Mass Air Flow (MAF) Sensor (3 Of 3). Scheme 136

Scheme 137

1. Check specified values for mass air flow sensor (display fields 1 and 2). (Scheme 140) (Scheme 140): Display Group 7: Mass Air Flow (MAF) Sensor

If the displayed values are not OK

1. Check intake air system for intake air system for leaks ("false air").

If there are no leaks

1. Check MAF sensor voltage supply. See «CHECKING MAF SENSOR -G70»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__checking-maf-sensor-g70) .
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

Checking MAF sensor -G70

1. Check fuse for MAF sensor (E-box in plenum).

If fuse is OK

Scheme 138

1. Remove upper air cleaner housing.
2. Disconnect MAF sensor harness connector.
3. Connect VAG1527B LED voltage tester between harness connector terminal 3 and engine Ground. (Scheme 141): Identifying MAF Sensor Harness Connector Terminals
4. Briefly operate starter (engine can start briefly). LED must light up.

If LED does not light

Scheme 139

1. Check wiring for open circuit or short to Ground between connector terminal 3 and fuse. (Scheme 142): Identifying MAF Sensor Harness Connector Terminals

If fuses and wiring are OK but LED still does not light

1. Check fuel pump relay. See «FUEL PUMP RELAY, CHECKING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__fuel-pump-relay-checking) .

If voltage supply is OK

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring for open or short circuits between MAF sensor connector terminal 1 (Ground) and ECM/test box socket E7. see scheme 139: Identifying MAF Sensor Harness Connector Terminals
3. If necessary, repair open circuit between connector terminal 1 and ECM terminal E7.

If voltage supply is OK

1. Check signal wiring. see scheme 140: Identifying ECM Connectors

Checking MAF sensor signal wiring

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Check wiring and connections for open or short circuits as follows: MASS AIR FLOW SENSOR CIRCUIT TEST: OPENS/SHORTS Mass Air Flow (MAF) sensor -G70- connector terminal VAG1598/19 test box socket (ECM terminal) 2 B18 4 B19

If wiring and connections are OK

1. Check intake air system for leaks ("false air").

If there are no leaks

1. Replace MAF sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). see scheme 141: Identifying ECM Connectors

Engine Speed (RPM) sensor, checking

Location of RPM sensor -G28-, see COMPONENT LOCATIONS, OVERVIEW .

1. RPM sensor properly installed (firmly seated)
2. No metal shavings or damage on RPM sensor or sensor wheel

Scheme 140

1. Disconnect gray harness connector from RPM sensor.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and measure resistance between connector terminals 1 and 2, using adapter cables from VAG1594 connector test kit. Specified value: approx. 0.5 to 2 kohm (Scheme 146): Identifying Engine Speed (RPM) Sensor Connector Terminals

If resistance is outside specified range

1. Replace RPM sensor.

If resistance is OK

1. Check resistance between terminals 1 and 3, and between terminals 2 and 3. Specified value: infinite ohm (no continuity)

If resistance is not as specified (infinite)

1. Replace RPM sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

If resistance was as specified (no continuity)

Scheme 141

Scheme 142

1. Check wiring between RPM sensor connector ECM as follows
2. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
3. Check wiring for open circuit, or short circuit to B+ or Ground, between 3-pin connector (sensor coupling) and ECM. (Scheme 147): Identifying Engine Speed (RPM) Sensor Harnesss Connector Terminals ENGINE SPEED (RPM) SENSOR CIRCUIT TEST RPM sensor coupling terminal VAG1598/19 test box socket (ECM terminal) 1 A18 2 A17 3 D11 (Ground)
4. If there are no open or short circuits
5. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). (Scheme 148): Identifying ECM Sensor Connectors

Engine Coolant Temperature (ECT) sensor, checking

Location of ECT sensor -G62-, see COMPONENT LOCATIONS, OVERVIEW .

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1552 Scan Tool Display - Engine Coolant Temperature (ECT) Sensor (1 Of 3). Scheme 143

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Engine Coolant Temperature (ECT) Sensor (2 Of 3). Scheme 144

1. Press buttons -0-, -0- and -3- to input display group number 3 (003), and press -Q- button to confirm input.

Indicated on display

VAG1552 Scan Tool Display - Engine Coolant Temperature (ECT) Sensor (3 Of 3). Scheme 145

Scheme 146

Scheme 147

Scheme 148

1. Check specified values for basic functions at engine idle speed (display field 3). see scheme 148 see scheme 148: Display Group 3: Basic Functions, Engine Idle Speed
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input. NOTE: The ECT sensor -G62- is a temperature-dependant resistor. If moisture should get into the connector (creating parallel resistance and causing an error in the sensor signal) the error can put the signal outside the range that is recognized by the ECM. If an ECT sensor malfunction is stored, the ECM calculates a replacement ECT value.
4. Disconnect ECT sensor harness connector.
5. Connect multimeter US1119 (Fluke 83 or equivalent) and measure resistance across sensor terminals 1 and 2, using adapter cables from VAG1594 connector test kit. see scheme 149: Identifying ECT Sensor Connector Terminals Specified resistance value (vs. temperature) (Scheme 152)(Scheme 152): ECT Sensor Resistance Versus Temperature Graph

If resistance is outside specified range

1. Replace ECT sensor.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) . If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

If resistance is OK

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Disconnect ECT sensor harness connector.
3. Check wiring for open circuit or short circuit to B+ or Ground between 2-pin harness connector and ECM. ECT SENSOR CIRCUIT TEST: OPENS/SHORTS 2-pin ECT sensor connector terminal VAG1598/19 test box socket (ECM terminal) 1 A23 2 A19 (Scheme 153): Identifying ECT Sensor Harness Connector Terminals

If no wiring or sensor malfunctions are found

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). (Scheme 154): Identifying ECM Sensors Connectors

Intake Air Temperature (IAT) sensor, checking

Location of IAT sensor -G42-, see COMPONENT LOCATIONS, OVERVIEW .

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01. See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Intake Air Temperature Sensor, Checking (1 Of 3). Scheme 149

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Intake Air Temperature Sensor, Checking (2 Of 3). Scheme 150

1. Press buttons -0-, -0- and -3- to input display group number 3 (003), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Intake Air Temperature Sensor, Checking (3 Of 3). Scheme 151

Scheme 152

1. Check specified values for basic functions at engine idle speed (display field 4). see scheme 156 see scheme 156: Display Group 3: Basic Functions, Engine Idle Speed
2. Press -->button to advance program sequence.
3. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.

If the ECM-calculated replacement value (20 °C) is displayed

Scheme 153

1. Disconnect IAT sensor harness connector.
2. Connect multimeter US 1119 (Fluke 83 or equivalent) and measure resistance across of IAT sensor terminals. (Scheme 158): Checking IAT Sensor Resistance Specified values (vs. sensor temperature): At 0°C: approx. 14.80-18.00 kohm At 20°C: approx. 5.60-6.80 kohm At 40°C: approx. 2.30-2.90 kohm At 60°C: approx. 1.00-1.40 kohm

If resistance values differ from specified values

Scheme 154

1. Replace IAT sensor -G42-.
2. Check readiness code. See «READINESS CODE, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). If DTC memory has been erased, generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz).
3. If resistance values are OK
4. Check wiring between ECM as follows
5. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
6. Check wiring for open circuit or short circuit to B+ or Ground between 2-pin IAT sensor connector and ECM. IAT SENSOR CIRCUIT TEST 2-pin IAT sensor connector terminal VAG1598/19 test box socket (ECM terminal) 1 A22 2 A19 see scheme 158: Identifying IAT Sensor Harness Connector Terminals

If there are no wiring or sensor malfunctions

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal). Generate new readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). see scheme 159: Identifying ECM Sensors Connectors

Air conditioning signals, checking

Note. When A/C is switched on, Engine Control Module (ECM) terminal C14 receives a positive (+) voltage signal.

1. Vehicle at room temperature, greater than 15°C (59°F)
2. No A/C malfunctions stored in DTC memory
3. Engine Coolant Temperature (ECT) at least 85°C (185°F)
4. ECM coding OK
5. Transmission selector lever in Neutral position
6. Rear window defogger switched off

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - A/C Signals, Checking (1 Of 3). Scheme 155

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - A/C Signals, Checking (2 Of 3). Scheme 156

1. Press buttons -0-, -2- and -1- to input display group number 21 (021), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - A/C Signals, Checking (3 Of 3). Scheme 157

Scheme 158

1. Check specified values for A/C operating conditions (display fields 2 and 3) (Scheme 163) (Scheme 163): Display Group 21: Operating Conditions
2. Switch A/C on; press "Auto" button; set "-" or "+" buttons for maximum heating, or maximum cooling, as specified. Specified value in display field 2: A/C-High Specified value in display field 3: Compr. on

If specified values are not displayed

1. Stop engine (switch ignition off).
2. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
3. Connect VAG1527B LED voltage tester between ECM/test box sockets C14 and D11 (Ground).
4. Switch ignition on.
5. Switch A/C on. LED must light up.

If LED does not light

1. Check wiring for open or short circuit between ECM/test box socket C14 and A/C control head E87-.

Identifying ECM Connectors. Scheme 159

If wiring and connections are OK

1. Check function of A/C control head. See «ON BOARD DIAGNOSTIC (OBD)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .

Rear window defogger signal, checking

Note. The Engine Control Module (ECM) receives a positive (+) voltage signal at terminal C22 when the rear window defogger is switched on.

1. Vehicle at room temperature, greater than 15°C (59°F)
2. Engine Coolant Temperature (ECT) at least 85°C (185°F)
3. ECM coding OK
4. Transmission selector lever in Neutral position
5. Rear window defogger switched off

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Rear Window Defogger System (1 Of 3). Scheme 160

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Rear Window Defogger System (2 Of 3). Scheme 161

1. Press buttons -0-, -2- and -4- to input display group number 24 (024), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Rear Window Defogger System (3 Of 3). Scheme 162

1. Check specified values for rear window defogger operating condition (display field 4). see scheme 168 Specified value in display field 4: "R Def OFF" see scheme 168: Display Group 24: Rear Window Defogger
2. Switch rear window defogger on. Specified value in display field 4: "R Def ON"
3. Press -->button to advance program sequence.
4. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
5. Stop engine (switch ignition off).
6. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
7. Connect VAG1527B LED voltage tester between ECM/test box sockets C22 and D11 (Ground).
8. Switch ignition on.
9. Switch rear window defogger on. LED must light up.

If LED does not light

Scheme 163

1. Check for open circuit between ECM/test box socket C22 and rear window defogger switch. see scheme 169: Identifying ECM Sensors Connectors

Engine Speed (RPM) signal, checking

Note. The RPM signal is required for the tachometer, ABS control module and the A/C system. The RPM signal, generated by the Engine Speed (RPM) sensor -G28-, is processed and distributed by the Engine Control Module (ECM).

Check RPM signal as follows

1. Connect VAG1551 Scan Tool ( «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) ) and press -0- button twice, to select "Automatic Test Sequence" function 00. There must be no malfunctions stored in Diagnostic Trouble Code (DTC) memory that refer to "Missing RPM Signal."

If DTCs indicating missing RPM signal are stored

1. Check wiring for short circuit between appropriate control module and ECM.

Vehicle Speed Sensor (VSS) signal, checking

Note. The vehicle speed signal is generated by the Vehicle Speed Sensor (VSS) at the transmission and processed in the instrument cluster.

Requirement

1. Speedometer function and display OK

1. If speedometer does not indicate vehicle speed: See «INSTRUMENTS»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#instruments) .

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Vehicle Speed Sensor, Checking (1 Of 3). Scheme 164

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Vehicle Speed Sensor, Checking (2 Of 3). Scheme 165

1. Press buttons -0-, -0- and -8- to input display group number 8 (008), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Vehicle Speed Sensor, Checking (3 Of 3). Scheme 166

1. Check specified value for vehicle speed (display field 4). (Scheme 170) (Scheme 170): Display Group 8: Vehicle Speed
2. Road test. WARNING: When driving or riding in an airbag-equipped vehicle, NEVER hold the scan tool or other test equipment in your hands or lap while in motion. Objects between you and the airbag increase the risk of injury in an accident. During a test drive in an airbag-equipped vehicle, test equipment must always be fastened to and operated from the rear seat by a second technician.
3. Check value in display field 4. Actual vehicle speed must be displayed (compare with vehicle speed indicated on speedometer).

If speed is not indicated

1. Press -->button to advance program sequence.
2. Press buttons -0- and -6- to select "End Output" function 06, and press -Q- button to confirm input.
3. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
4. Check wiring for continuity or short circuit between ECM/test box socket C13 and instrument cluster.
5. Check wiring to all additional users of vehicle speed signal (e.g. radio, automatic transmission, A/C, etc.) according to wiring diagrams. Test each system, one at a time, and continue testing to isolate cause of malfunction.

Automatic transmission selector lever position signal, checking

Note. The multi-function Transmission Range (TR) switch -F125- at the transmission switches to Ground at Engine Control Module (ECM) terminal B11 when the selector lever is in the P (Park) or N (Neutral) positions. The ECM sends a signal (via terminal C16) to the shiftlock relay. If one or both connections are interrupted, the engine cannot be started. When a transmission drive range is selected, ECM terminal B11 is switched to B+. The signal is not processed via ECM terminal B11, but is transmitted through the CAN-bus.

1. Connect VAG1551 or VAG1552 Scan Tool (ST) and press buttons -0- and -1- to insert "Engine Electronics" address word 01 (engine running at idle). See «VAG1551 OR VAG1552 SCAN TOOL (ST), CONNECTING AND SELECTING "ENGINE ELECTRONICS" ADDRESS WORD 01»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Automatic Transmission Selector Lever Position (1 Of 3). Scheme 167

1. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08, and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Automatic Transmission Selector Lever Position (2 Of 3). Scheme 168

1. Press buttons -0-, -2- and -1- to input display group number 21 (021), and press -Q- button to confirm input.

Indicated on display

VAG1551 or VAG1552 Scan Tool Display - Automatic Transmission Selector Lever Position (3 Of 3). Scheme 169

1. Check specified values for automatic transmission selector lever position (display field 1). (Scheme 172) Specified value in display field 1: "Neutral" (Scheme 172): Display Group 21: Operating Conditions
2. Press brake pedal and select transmission drive range. Specified value in display field 1: "1st TR"

If display is not as specified

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Connect VAG1527B LED voltage tester between ECM/test box sockets D9 (B+, terminal 30) and B11. LED must go out when a transmission drive range is selected. see scheme 178: Identifying ECM Sensors Connectors

If LED does not go out, and the display is not OK

1. Disconnect harness connector from multi-function Transmission Range (TR) switch.
2. Check wiring for open or short circuits.

If wiring is OK

1. Check multi-function TR switch. See «ELECTRICAL TESTING»(/audi/a8/d2-1994-1999/remont/automatic-trans/#on-board-diagnostic-obd-5-spd-automatic-transmission-01v-fwd__electrical-testing) (FWD vehicles) or «ELECTRICAL TESTING»(/audi/a8/d2-1994-1999/remont/automatic-trans/#on-board-diagnostic-obd-5-spd-automatic-transmission-01l-awd__electrical-testing) (AWD vehicles).

CAN-bus data exchange between Motronic ECM and automatic transmission TCM, checking

1. Check Diagnostic Trouble Code (DTC) memory for Transmission Control Module (TCM). See «ON BOARD DIAGNOSTIC (OBD) - 5 SPD. AUTOMATIC TRANSMISSION (01L - AWD)»(/audi/a8/d2-1994-1999/remont/automatic-trans/#on-board-diagnostic-obd-5-spd-automatic-transmission-01l-awd) or «ON BOARD DIAGNOSTIC (OBD) - 5 SPD. AUTOMATIC TRANSMISSION (01V - FWD).»(/audi/a8/d2-1994-1999/remont/automatic-trans/#on-board-diagnostic-obd-5-spd-automatic-transmission-01v-fwd) .
2. Switch ignition off.
3. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
4. Check wiring for open or short circuit between TCM and ECM/test box sockets A9 and A10.

If wiring is OK

Scheme 170

1. Temporarily replace ECM and/or TCM.
2. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz). see scheme 179: Identifying ECM Sensors Connectors

CAN-bus data exchange between Motronic ECM and ABS control module, checking

DTC table indicates that CAN-bus be checked.

1. Check DTC memory of ABS control module. See «ON BOARD DIAGNOSTIC (OBD)»(/audi/a8/d2-1994-1999/remont/warning-system/#on-board-diagnostic-obd-absedlasr) .

If a DTC pertaining to the CAN-bus is stored

1. Switch ignition off.
2. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
3. Check wiring from terminals C1 and C19 on Engine Control Module (ECM) to ABS control module for open or short circuit.
4. If wiring connection is OK, replace either ABS control module or ECM. see scheme 180: Identifying ECM Sensors Connectors

Traction control (ASR) signal, checking

(ASR = Antriebs-Schlupf-Regelung)

1. Check coding for Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) CODING, CHECKING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__engine-control-module-ecm-coding-checking) .

If coding is OK

1. Check Diagnostic Trouble Code (DTC) memory for ABS control module. See «ON BOARD DIAGNOSTIC (OBD)»(/audi/a8/d2-1994-1999/remont/warning-system/#on-board-diagnostic-obd-absedlasr) .

If no DTCs are recognized

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) .
2. Check wiring for open or short circuit between ECM/test box socket C24 and ABS control module.

Identifying ECM Sensors Connectors. Scheme 171

If wiring and ABS control module are OK

1. Replace ECM. See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) .
2. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

Fuel level status, checking

Note. If little fuel remains in the fuel tank, less than approx. 12 liters (3 gallons), misfiring and fuel system malfunctions can result. Also, the malfunction "Fuel Level too Low" (SAE P1250/VAG17658) may be stored in Diagnostic Trouble Code (DTC) memory. The malfunction "Fuel Level too Low" is always recognized and stored when there are misfiring or fuel system malfunctions. As a rule, always eliminate the misfiring and other fuel system malfunctions first.

1. Fill fuel tank with at least 20 liters (5-1/2 gallons).
2. Check DTC memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) . And erase memory. See «ERASE DTC MEMORY, (SCAN TOOL FUNCTION 05)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .
3. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .
4. Road test.
5. Check DTC memory. See «CHECK DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, (SCAN TOOL FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz__check-diagnostic-trouble-code-dtc-memory) .

If "Fuel Level too Low" is the only malfunction stored in DTC memory (SAE P1250/VAG17658)

1. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting).
2. Check wiring for short circuit to Ground between ECM/test box socket C8 and instrument cluster. see scheme 182: Identifying ECM Sensors Connectors

Malfunction Indicator Lamp (MIL) function, checking

1. Switch ignition on. MIL must light up.

If MIL does not light

1. Switch ignition off.
2. Connect VAG1598/19 test box to ECM harness connector. See «VAG1598/19 TEST BOX, CONNECTING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__vag159819-test-box-connecting) . Connect jumper wire between sockets C9 and D11 (Ground).
3. Switch ignition on. MIL must light up.

If MIL now lights (with jumper wire connected)

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a8/d2-1994-1999/remont/fuel-system/#multiport-fuel-injection-mfi-37l-42l-v8-4v-aew-abz__engine-control-module-ecm-without-metal) .
2. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a8/d2-1994-1999/remont/ignition-system/#on-board-diagnostic-obd-37l-42l-v8-aew-abz) .

If MIL still does not light

Scheme 172

1. Switch ignition off.
2. Check MIL bulb. see scheme 183: Identifying ECM Connectors

If MIL bulb is OK

1. Check wiring for open or short circuit between ECM/test box socket C9 and instrument cluster.

If wiring is OK

1. Check voltage supply from instrument cluster. See «INSTRUMENTS»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#instruments) .

If the MIL lights up when the engine is running, and only P1690/18098 is stored in DTC memory

1. Stop engine (switch ignition off).
2. Disconnect ECM harness connector.
3. Switch ignition on.

If MIL stays on

1. Check wiring for short circuit to Ground between ECM connector terminal C9 and instrument cluster.

See also:
• ERASE DTC MEMORY, (SCAN TOOL FUNCTION 05)
• Check Diagnostic Trouble Code (DTC) Memory, (scan tool function 02)
• OUTPUT DIAGNOSTIC TEST MODE (DTM), (SCAN TOOL FUNCTION 03)
• BASIC SETTING, (SCAN TOOL FUNCTION 04)
• ENGINE CONTROL MODULE (ECM) CODING, CHECKING
• FUEL PUMP CHECK VALVE, CHECKING
• ACCELERATOR PEDAL CABLE, ADJUSTING
• ON BOARD DIAGNOSTIC (OBD)
• INSTRUMENTS
• ELECTRICAL TESTING
• ELECTRICAL TESTING
• ON BOARD DIAGNOSTIC (OBD) - 5 SPD. AUTOMATIC TRANSMISSION (01L - AWD)
• ON BOARD DIAGNOSTIC (OBD) - 5 SPD. AUTOMATIC TRANSMISSION (01V - FWD).
• ON BOARD DIAGNOSTIC (OBD)
• FUEL PRESSURE REGULATOR AND RESIDUAL FUEL PRESSURE, CHECKING
• OXYGEN SENSOR (O2S) HEATING, CHECKING
• MOTRONIC MULTIPORT FUEL INJECTION (MFI) SYSTEM, SERVICING
• RULES OF CLEANLINESS
• ENGINE CONTROL MODULE (ECM) (WITH METAL ANTI-THEFT HOUSING), REPLACING
• COMPONENT LOCATIONS, OVERVIEW
• ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING
• VAG1598/19 TEST BOX, CONNECTING
• INSTALLING
• HEATED OXYGEN SENSOR (HO2S) SIGNAL WIRING AND WIRING CONNECTIONS, CHECKING
• OXYGEN SENSOR (O2S) BEHIND THREE WAY CATALYTIC CONVERTER (TWC) SIGNAL WIRING AND WIRING CONNECTIONS, CHECKING
• IF SPECIFIED VALUES ARE NOT DISPLAYED
• CLOSED THROTTLE POSITION (CTP) SWITCH, CHECKING
• CHECKING IDLE AIR CONTROL SIGNAL FROM ECM
• INTAKE MANIFOLD TUNING (IMT) VALVE FUNCTION, CHECKING
• FUEL PUMP RELAY, CHECKING
• ADJUSTING
• CHECKING MAF SENSOR -G70