Multiport Fuel Injection (mfi) - 2.8l v6 Atq Audi A6 C5

Safety precautions

If special testing equipment is required during road test, note the following

To reduce the risk of personal injury and/or damage to the fuel injection and ignition system, always observe the following

1. Only disconnect and reconnect wires for injection and ignition system, including test leads, when ignition is turned off.
2. If engine is to be cranked at starting RPM without starting (e.g. for compression testing), disconnect connector from ignition coils and from fuel injectors.
3. It is possible that the control module will recognize a malfunction and store a DTC during some tests. After completing all tests and repairs, DTC memory should therefore be checked and erased if necessary. Readiness code must be generated after DTC memory is erased. See «READINESS CODE, GENERATING»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) .
4. Always switch ignition off before cleaning engine.
5. The battery should only be disconnected and reconnected when the ignition is turned off, since otherwise the Engine Control Module (ECM) can be damaged.

Rules of cleanliness

When working on the fuel supply or fuel injection systems, the following "6 rules of cleanliness" should be carefully observed

1. Thoroughly clean all connections and the surrounding area before disconnecting.
2. Place parts that have been removed on a clean surface and cover. Use lint-free cloths only!
3. Carefully cover opened components or seal them if repairs are not carried out immediately.
4. Only install clean components: Only unpack replacement parts immediately prior to installation. Do not use parts that have been stored loose (in tool boxes etc.)
5. When the system is open: Do not work with compressed air if it can be avoided. Do not move vehicle unless absolutely necessary.
6. Disconnected electrical harness connectors: Protect from dirt and moisture. Be sure harness connector is dry before connecting.

Technical data

TECHNICAL DATA

Component locations, overview

Note. Other component Locations (Scheme 398), up to (Scheme 403). Component Locations without illustration: - Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130- with Oxygen Sensor (O2S) Heater 1 -Z29- Bank 2, sensor 1 Accessible from below after vehicle has been lifted - Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131- with Oxygen Sensor (O2S) Heater 2 -Z30- Bank 2, sensor 2 Accessible from below after vehicle has been lifted - Leak Detection Pump (LDP) - V144- Below rear left wheelhousing liner

Note. Items 1 to 15 in the following list refer (Scheme 396).

Scheme 396

1. 4-pin harness connector for Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- and Oxygen Sensor (O2S) Heater 1 -Z29- (bank 1 sensor 2) green
2. 4-pin harness connector for Oxygen Sensor (O2S) 2 behind Three Way Catalytic Converter (TWC) -G131- and Oxygen Sensor (O2S) Heater 2 -Z30- (bank 2 sensor 2) brown
3. 4-pin harness connector for Heated Oxygen Sensor (HO2S) -G39- before catalytic converter and Oxygen Sensor (O2S) Heater -Z19- (bank 1 sensor 1) Black
4. 3-pin harness connector for Knock Sensor (KS) 1 -G61- blue
5. Secondary Air Injection (AIR) solenoid valve -N112
6. Intake Air Temperature (IAT) sensor -G42
7. 4-pin harness connector for Heated Oxygen Sensor (HO2S) 2 -G108- before catalytic converter and Oxygen Sensor (O2S) 2 Heater -Z28- (bank 2 sensor 1) Black
8. 3-pin harness connector for engine speed (RPM) sensor - G28- gray
9. 3-pin harness connector for Knock Sensor (KS) 2 -G66- blue
10. E-box in plenum chamber Motronic Engine Control Module (ECM) -J220- Secondary Air Injection (AIR) Pump Relay -J299-. See «COMPONENT LOCATION FOR SECONDARY AIR INJECTION (AIR) PUMP RELAY -J299»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq).
11. Valve -2- for camshaft adjustment - N208
12. Camshaft Position (CMP) sensor - G40- Bank 1
13. Heated Oxygen Sensor (HO2S) - G39- before catalytic converter with Oxygen Sensor (O2S) Heater - Z19- Bank 1, sensor 1
14. Ground connection on the engine bracket, right side
15. Mass Air Flow (MAF) sensor -G70- Checking, see «MASS AIR FLOW (MAF) SENSOR -G70-, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) (Scheme 396): Identifying Motronic Injection System Component Locations (Items 1 To 15) NOTE: Items 16 to 29 (Scheme 397)
16. Evaporative Emission (EVAP) canister purge regulator valve - N80
17. Engine Coolant Temperature (ECT) sensor -G62- for Engine Control Module (ECM) At coolant line behind cylinder head engine bank 1 with Engine Coolant Temperature (ECT) Sensor -G2- Checking, see «ENGINE COOLANT TEMPERATURE (ECT) SENSOR -G62-, CHECKING»(/audi/a6/c5-1997-2001/remont/ignition-system/#ignitionglow-plug-system-28l-v6-atq). If necessary, release pressure in cooling system before removing
18. Throttle valve control module - J338- With throttle drive (power accelerator actuation) -G186-, angle sensor -1- for throttle drive (power accelerator actuation) - G187-, and angle sensor -2- for throttle drive (power accelerator actuation) -G188
19. Intake Manifold Change -Over Valve -N156
20. Fuel pressure regulator
21. Engine Speed (RPM) sensor -G28- in transmission housing via ring gear Checking, see «ENGINE SPEED (RPM) SENSOR -G28-, CHECKING»(/audi/a6/c5-1997-2001/remont/ignition-system/#ignitionglow-plug-system-28l-v6-atq).
22. Camshaft Position (CMP) sensor 2 -G163- Bank 2
23. Heated Oxygen Sensor (HO2S) 2 - G108- before catalytic converter with Oxygen Sensor (O2S) 2 Heater -Z28- Bank 2, sensor 1
24. Knock Sensor (KS) 2 -G66
25. Ignition coils ( -N-, -N128-, -N158-) with power output stage -N122
26. Knock Sensor (KS) 1 -G61
27. Fuel injectors -N30- through -N33-, Cylinder 5/6 Fuel Injector -N83-, - N84
28. Valve -1- for camshaft adjustment - N205
29. Secondary Air Injection (AIR) pump motor-V101

Identifying Motronic Injection System Component Locations (Items 16 To 29). Scheme 397

Identifying Electronic Power Control (EPC) Warning Lamp. Scheme 398

Identifying Throttle Position (TP) Sensor And Sender 2 For Accelerator Pedal Position. Scheme 399

Component location Brake Light Switch -F-, Brake Vacuum Vent Valve Switch for Cruise Control/Diesel Fuel Injection -F47- and Clutch Vacuum Vent Valve Switch -F36

1. Clip
2. Brake Light Switch -F-, Brake Vacuum Vent Valve Switch For Cruise Control/Diesel Fuel Injection -F47
3. Clutch vacuum vent valve switch -F36

Note. In order to assure sufficiently secure fitting, switches must not be installed more than once.

Adjusting switch: , see BRAKELIGHT SWITCH .

Identifying Brake Light Switch, Brake Vacuum Vent Valve Switch For Cruise Control/Diesel Fuel Injection. Scheme 400

Identifying Secondary Air Injection (Air) Pump Relay. Scheme 401

Secondary Air Injection (AIR) Pump Relay -J299- (arrow) in 3-pin relay carrier in E -box, plenum chamber.

Component locations Fuel Pump (FP) Relay -J17

Fuel Pump (FP) Relay -J17- is located at position 4 of centered electrics in driver's footwell, left.

Identifying Fuel Pump (FP) Relay - Position 4. Scheme 402

Component location of Data Link Connector (DLC)

Data Link Connector (DLC) in knee bolster on driver's side.

Identifying Data Link Connector (DLC). Scheme 403

Air filter, disassembling and assembling

Note. The following list refers to items in (Scheme 404).

1. Cover
2. Air duct to metering unit
3. Mass Air Flow (MAF) sensor -G70
4. 10 Nm
5. Connection hose
6. Seal
7. Air filter, upper portion
8. Rubber grommet
9. Filter element
10. Air filter, lower portion

Exploded View Of Mass Air Flow Sensor And Air Filter Assembly. Scheme 404

Intake manifold change-over components, removing and installing

Note. The following list refers to items in (Scheme 405).

1. Vacuum setting element
2. Compression spring
3. Rotary change -over valve
4. Intake Manifold
5. Check -valve Installed position: blue side toward Y-piece
6. Y-piece
7. Intake manifold change -over valve -N156
8. 10 Nm
9. Securing plate
10. Rubber grommet
11. Spacer sleeve
12. Washer conical side toward intake manifold
13. Seal Replace if damaged
14. Seal for rotary change -over valve Replace if damaged
15. 6 Nm

Exploded View Of Intake Manifold Change-Over Components. Scheme 405

Wire and component test using VAG1598/31 test box

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. For procedure, see ENGINE CONTROL MODULE (ECM) (WITH METAL ANTI-THEFT HOUSING), REPLACING . After repairs are complete, the metal anti-theft housing must be reinstalled. VAG1598/31 test box is designed so that it can be simultaneously connected to the wiring harness at the Engine Control Module (ECM) and also to the ECM itself. This is advantageous because electronic engine control remains fully functional (e.g. measurement of signals with engine running) when the test box is attached. Relevant test procedures note whether Engine Control Module (ECM) should also be connected to the test box or not. Always use VAG1594A connector test kit to attach measurement devices (e.g. VAG1527B voltage tester, VAG1526 multimeter etc.).

Identifying VAG1598/31. Scheme 406

1. VAG1598/31

Scheme 407

Scheme 408

Scheme 409

Scheme 410

1. Switch ignition off.
2. Pull off rubber seal of plenum chamber cover in direction of arrow. (Scheme 407): Pulling Off Rubber Seal Of Plenum Chamber Cover
3. Remove cover -1- toward front.
4. Remove E-box cover (arrows). (Scheme 408): Removing E-Box Cover
5. Using a screwdriver, carefully pry off retaining bracket (arrow). (Scheme 409): Prying Off Control Module Retaining Bracket
6. Disengage locking lugs and remove control module connector. NOTE: Adaptation values are erased when connector is disconnected from the Engine Control Module (ECM), DTC memory content remains intact.
7. Connect VAG1598/31 test box to connector of wiring harness. Ground (GND) clip at test box (not visible in illustration) must be connected to Ground (GND). Relevant test procedures note whether Engine Control Module (ECM) should also be connected to test box. (Scheme 410): Connecting VAG1598/31 Test Box To Connector Of Wiring Harness
8. Perform test as described in relevant repair sequence. NOTE: After re-connecting the Engine Control Module (ECM), the following work steps must be performed
9. Check DTC memory and erase it if necessary. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and).
10. Perform adaptation of Throttle Valve Control Module -J338-. See «THROTTLE VALVE CONTROL MODULE, ADAPTING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__throttle-valve-control-module-adapting). NOTE: In the first adaptation phase during engine basic setting, it is possible that idle will be rough and vehicle may shake lightly in drive mode.

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

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

Scheme 411

1. VAS5051 with VAG5051/1 or (Scheme 411): Identifying VAS5051 With VAG5051/1
2. VAG1551 with VAG1551/3B

Removing

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

VAG1551 Scan Tool (ST) display indicates control module identification. For example (Scheme 412)

Identifying VAG1551 Scan Tool (ST) Display - Control Module Identification (Example). Scheme 412

Scheme 413

Scheme 414

Scheme 415

1. First, always allow display of control module identification and print it out.
2. Compare coding with coding versions. See «CODING TABLE»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__coding-table).
3. Switch ignition off.
4. Pull off rubber seal of plenum chamber cover in direction of arrow. (Scheme 413): Pulling Off Rubber Seal Of Plenum Chamber Cover
5. Remove cover -1- toward front.
6. Remove E-box cover (arrows). (Scheme 414): Removing E-Box Cover
7. Using a screwdriver, carefully pry off retaining bracket (arrow). (Scheme 415): Removing Engine Control Module (ECM)
8. Disengage locking lugs and remove control module connector.
9. Remove Engine Control Module (ECM).

Installing

Installation is reverse of removal, noting the following

Note. After installing new Engine Control Module (ECM), the following work steps must be performed

1. Check DTC memory and erase it if necessary. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) .
2. Perform adaptation of Throttle Valve Control Module -J338-. See «THROTTLE VALVE CONTROL MODULE, ADAPTING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__throttle-valve-control-module-adapting) .
3. Observe notes for coding new Engine Control Module (ECM). See «CODE CONTROL MODULE (FUNCTION 07)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__code-control-module-function-07) .
4. For vehicles with cruise control (discernable at steering column), switch this free in ECM: For models up to 2000 m.y., see «CRUISE CONTROL SYSTEM, ON BOARD DIAGNOSTIC»(/audi/a6/c5-1997-2001/remont/cruise-control-systems/#on-board-diagnostic-obd-up-to-2000) . For 2001 models, see «CRUISE CONTROL SYSTEM, ON BOARD DIAGNOSTIC»(ref-196304-S13409621632005100900000) .
5. Adapt immobilizer to Engine Control Module (ECM): See «ANTI-THEFT IMMOBILIZER, ON BOARD DIAGNOSTIC (OBD)»(ref-196304-S26057683262005100900000) .
6. For vehicles with automatic transmission, kick down function must be learned. See «KICK DOWN FUNCTION, ADAPTING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__kick-down-function-adapting) .
7. Generate readiness code. See «READINESS CODE, GENERATING»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . NOTE: In the first adaptation phase during engine basic setting, it is possible that idle will be rough and vehicle may shake lightly in drive mode.

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

Removing ECMs 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), Diagnostic Trouble Code (DTC) memory content remains intact.

Scheme 416

Scheme 417

Scheme 418

Scheme 419

1. Connect VAS5051 tester and select vehicle system "01 - Engine Electronics". Ignition must be switched on for this. (Scheme 416): VAS5051 Tester Display VAS5051 tester display will indicate the control module identification and coding -2-.
2. Always allow display of control module identification first and print it out.
3. Switch ignition off.
4. Pull off of plenum chamber cover rubber seal in direction of arrow. (Scheme 417): Pulling Off Of Plenum Chamber Cover Rubber Seal
5. Remove cover -1- toward front.
6. Remove cover for E-box, plenum chamber (arrows). (Scheme 418): Removing Cover For E-Box, Plenum Chamber
7. Using a screwdriver, carefully pry off retaining bracket (arrow). (Scheme 419): Removing Retaining Bracket NOTE: Item -1- in illustration shows Engine Control Module (ECM) with anti - theft housing.

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-.

Identifying Engine Control Module (ECM) With Metal Anti-Theft Housing. Scheme 420

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

To disconnect the harness connector from 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

Identifying Heat Gun And Adapter Nozzle. Scheme 421

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

Procedure

Scheme 422

Scheme 423

Scheme 424

Scheme 425

Scheme 426

Scheme 427

1. "Flip" Engine Control Module (ECM) with anti -theft housing in direction of engine compartment so that locking mechanism (item -2- in illustration) becomes visible and place a clean rag below Engine Control Module (ECM) with anti -theft housing. (Scheme 422): Identifying Engine Control Module (ECM) With Metal Anti-Theft Housing
2. Adjust heat gun as shown in illustration, i.e. temperature adjustment -2- to maximum heat output and two-stage switch for air mass -3- to position 3. (Scheme 423): Identifying Adjust Heat Gun Switches 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 threads 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 and no parts that are in the vicinity become heated. If necessary, cover them.
3. Guide nozzle -1- of heat gun to locking mechanism threads so that nozzle "encloses" threads. It is OK to let nozzle make contact at upper end of metal anti -theft housing. (Scheme 424): Identifying Guide Nozzle Of Heat Gun
4. Switch on heat gun and heat up threads for approx. 20 to 25 seconds.
5. Next, using locking pliers -1-, grab screw head -2- and remove snap - off screw by turning in direction of arrow. (Scheme 425): Removing Snap Screw Procedure for the second snap -off screw is exactly the same. Be very careful since the control module harness connector is in close proximity.
6. Guide nozzle -1- of heat gun to locking mechanism threads again so that nozzle "encloses" threads. It is OK to let nozzle make contact at upper end of metal anti -theft housing. (Scheme 426): Identifying Guide Nozzle Of Heat Gun
7. Switch on heat gun and heat up threads for approx. 20 to 25 seconds.
8. Next, using locking pliers -1-, grab screw head -2- and remove snap - off screw by turning in direction of arrow. (Scheme 427): Removing Snap-Off Screw By Turning 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.

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 subject heading "Engine Control Module (ECM), replacing". Use VAS5051 tester to do so .

Identifying Special Tools And Equipment. Scheme 428

1. VAS5051 with VAG5051/1 or
2. VAG1551 with VAG1551/3B

Test requirements

1. Exhaust system free of leaks.
2. Coolant Temperature at least 80 °C.
3. Electrical consumers switched off (coolant fan must NOT run during test).
4. A/C switched off.
5. No pressure gauge connected.
6. Vehicles with automatic transmission Selector lever in P or N.

Test sequence

Note. Idle speed cannot be adjusted. Idle speed is checked during basic setting of the engine. During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

1. Check DTC Memory. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) . There must not be any DTCs stored, repair malfunctions if necessary, erase DTC memory, switch engine off and start again, road test vehicle and check DTC memory again as a control measure.
2. Let engine continue to run at idle.

When indicated on display

Identifying Scan Tool Display - Checking Idle Speed (RPM) (1 Of 4). Scheme 429

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Idle Speed (RPM) (2 Of 4). Scheme 430

1. Press buttons -0-, -5- and -6- to select "display group number 056" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Idle Speed (RPM) (3 Of 4). Scheme 431

1. Check whether engine speed in display field 1 (actual engine speed) is within tolerated range. DISPLAY GROUP 056: IDLE STABILIZATION WITH ENGINE AT IDLE AND OPERATING TEMPERATURE Display fields 1 2 3 4 Display group 056: Idle stabilization with engine at idle and operating temperature Display xxx /min xxx /min x.x% X X X X X Indicated Engine speed (actual) Engine speed (specified) Idle control Torque change Operating conditions Specified value 720 to 820 RPM (1) 670 to 770 RPM (2) 770 RPM (1) 720 RPM (2) -5 to 5% 0 0 0 0 0 Notes If specified value is not obtained «FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__fuel-pressure-regulator-and-residual-pressure) Significance of numbers «FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__fuel-pressure-regulator-and-residual-pressure) (1) Front Wheel Drive Vehicles (2) All-Wheel Drive Vehicles

Note. Engine speed in display field 1 (actual engine speed) is the current engine speed. Engine speed in display field 2 (specified engine speed) is a theoretical engine speed calculated by the ECM. At idle, the ECM always attempts to adapt the engine speed (actual) to the specified engine speed (specified). This means that the engine speed (actual) must always approximately match the engine speed (specified) at idle. Display fields 3 and 4 provide information, but are not relevant for checking idle speed.

If specified value is obtained

1. Press right arrow button.

Indicated on display (function selection)

Identifying Scan Tool Display - Checking Idle Speed (RPM) (4 Of 4). Scheme 432

If specified value is not obtained

1. Check DTC memory again. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) .
2. If DTC memory was erased, readiness code must be re -generated. See «READINESS CODE, GENERATING»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) .

If idle speed is too high or low and there are no DTCs in DTC memory, the following tests (marked with dots) must be performed

1. Unmetered air in intake air system: checking, see «INTAKE AIR SYSTEM, CHECKING FOR LEAKS (UNMETERED AIR)»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. Throttle valve control module: checking, see «THROTTLE VALVE CONTROL MODULE -J338 -, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__throttle-valve-control-module-j338) .
3. Evaporative Emission (EVAP) canister purge regulator valve always open: checking, see «TANK VENTILATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
4. Perform adaptation of throttle valve control module. See «THROTTLE VALVE CONTROL MODULE, ADAPTING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__throttle-valve-control-module-adapting) .

Significance of 5 digit indication of display group 056

SIGNIFICANCE OF 5 DIGIT INDICATION OF DISPLAY GROUP 056

Fuel pressure regulator and residual pressure, checking

Note. Fuel pressure regulator regulates fuel pressure according to intake manifold pressure. This ensures that the pressure drop at the fuel injectors remains the same for each speed and load range of the engine.

Identifying VAG 1318 With VAG 1318/7 Adapter. Scheme 433

1. VAG 1318 with VAG 1318/7 adapter, VAG 1318/8 pressure hose with connectors and VAG 1318/15 adapter

1. Fuel Pump (FP) OK: checking, see «FUEL PUMP (FP) RELAY -J17- AND ACTIVATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. Fuel Pump (FP) OK, checking: For FWD models, see «FUEL PUMP, CHECKING ELECTRICALLY»(/audi/a6/c5-1997-2001/remont/fuel-system/#fuel-supply-system-all-engines) . For AWD models, see «FUEL PUMP, CHECKING ELECTRICALLY»(/audi/a6/c5-1997-2001/remont/fuel-system/#fuel-supply-system-all-engines) .
3. Fuel filter OK
4. Battery voltage at least 12.7 V
5. Vehicles with automatic transmission Selector lever in P or N.

1. Remove engine cover (arrows).

Scheme 434

1. Connect VAG1318 pressure gauge using adapters VAG1318/7, /1318/8 pressure hose with connectors and 1318/15 adapter in supply line. (Scheme 435): Connecting VAG1318 Pressure Gauge Using Adapters VAG1318/7, /1318/8 Pressure Hose With Connectors
2. Disconnect vacuum hose from pressure regulator to intake manifold at pressure regulator and seal line. NOTE: If fuel should escape at the vacuum connection of the pressure regulator during the following pressure test, replace pressure regulator.
3. Start engine and let run at idle.
4. Measure fuel pressure. Specification: 3.8 to 4.2 bar
5. If specified value is not reached, replace pressure regulator on a trial basis and repeat pressure test.
6. If specified value is not reached again, check Fuel Pump (FP) or supply line for damage (e.g. pinched areas) and replace if necessary.
7. If specified value is exceeded, check return line for damage (e.g. pinched areas) and replace if necessary. NOTE: During the following test, the engine must not run for an unnecessarily long period of time with the vacuum hose removed. Otherwise, the higher fuel pressure can cause enrichment of the fuel to air ratio, which under some circumstances can cause the oxygen sensor control limits to be exceeded, causing a DTC to be stored.
8. Start engine and let run at idle.
9. Switch of electrical consumers (A/C system etc.).
10. Connect vacuum hose at pressure regulator while observing pressure drop at pressure gauge.
11. Fuel pressure must drop by approx. 0.5 bar when connecting vacuum hose. If the pressure change does not occur, the following tests must be performed: Check vacuum hose for tears and damage. Check vacuum hose at intake manifold for throughput by disconnecting from pressure regulator and blowing into it.
12. If no leaks can be detected and if vacuum hose has throughput, replace pressure regulator.

Scheme 435

1. Residual pressure 10 minutes after switching engine off (minimum pressure). Specified value with a cold engine: approx. 2.2 bar Specified value with the engine at operating temperature: approx. 3.0 bar NOTE: Pressure increase for an engine at operating temperature limited by the fuel expansion is normal.
2. Start engine and let run at idle.
3. Wait until pressure has dropped, and then switch off ignition. Simultaneously close shut-off valve of VAG1318 pressure gauge (pry perpendicular to direction of flow -arrow-). (Scheme 436): Closing Shut-Off Valve Of VAG 1318 Pressure Gauge

The following malfunction are possible if the pressure does not drop

1. There is a leak in the threaded connection between the pressure gauge and the fuel supply line
2. There is a leak at the supply line at fuel tank.
3. There is a leak in the check valve in the Fuel Pump (FP).

See FUEL SUPPLY, FRONT WHEEL DRIVE (FWD) or FUEL SUPPLY, ALL WHEEL DRIVE (AWD) .

Note. Pressure gauge displays the pressure behind the stopcock "intake manifold side" after the stopcock is closed (in direction of fuel injector, fuel pressure regulator). If the pressure drops in front of the stopcock (in direction of fuel tank), the device cannot detect it. For this reason, the center of this page states "If the pressure does not drop...".

The following malfunctions are possible if the pressure drops again

1. Fuel pressure regulator faulty
2. Fuel injectors not properly sealed
3. Threaded connections of pressure gauge behind stopcock is not properly sealed.

Note. Close stopcock for removing the pressure gauge, loosen threaded connection at VAG1318/15 adapter and let excess fuel escape into catch reservoir by opening stopcock.

Scheme 436

1. VAG1526A
2. VAG1527B
3. VAG1594A
4. VAG1598/31 (Scheme 437): Identifying Special Tools And Equipment

Scheme 437

Scheme 438

1. Remove engine cover (arrows). (Scheme 438): Removing Engine Cover
2. Disconnect harness connector at fuel injector to be tested.
3. Connect multimeter at valve for resistance measurement. (Scheme 439): Checking Fuel Injector Resistance Specification: 13.5 to 15.5 ohms

With an engine at operating temperature, the resistance increases by approx. 4 to 6 ohms.

If specified value is not obtained

1. Replace fuel injector. See «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

1. Fuel Pump (FP) OK, checking. See «FUEL PUMP (FP) RELAY -J17- AND ACTIVATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. Fuse for fuel injectors OK

Scheme 439

1. Disconnect harness connector at fuel injector to be tested. (Scheme 440): Identifying Fuel Injector Harness Connector Terminals
2. Connect VAG1527B voltage tester as follows: FUEL INJECTOR CIRCUIT TEST: TERMINAL 1 Hararness connector Terminal Measure to 1 Engine Ground (GND)
3. Switch ignition on. LED must light up.

If LED does not light up

1. Check wire connection between terminal 1 and fuse for injector valves for open circuit
2. Repair open circuit if necessary.

If LED lights up

Scheme 440

1. Internal resistance of valve OK (Scheme 441): Sliding Back Rubber Grommet Of Fuel Injector Connector

1. Slide back rubber grommet of fuel injector connector (arrow), but leave connector connected.
2. Connect VAG1527B voltage tester between sockets 2 (signal) and 1 (B+).
3. Operate starter briefly (engine can also start). LED must blink.

Note. Voltage testers do not go out completely during low current pick -up between activations by the ECM, but rather continue to glow a little and then get slightly brighter during activation.

If LED does not blink

Scheme 441

1. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 47: Identifying Fuel Injector Harness Connector Terminals
2. Check following wire connections for open circuit and short circuit to Ground (GND) and B+: FUEL INJECTOR HARNESS CONNECTOR TERMINAL TEST CHART Cylinder Fuel injector harness connector Terminal VAG1598/31 test box Socket 1 2 96 2 2 112 3 2 88 4 2 97 5 2 113 6 2 89
3. Repair open circuit or short circuit if necessary.

If wire connection is OK

1. Replace Engine Control Module (ECM) «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Fuel rail with fuel injectors, disassembling and assembling

Note. The following list refers to items in (Scheme 442).

1. Fuel distributor
2. to T-piece
3. Retaining clip Check for secure fitting
4. O-ring Removing and installing, see «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) Always replace Coat with clean engine oil
5. Fuel pressure regulator
6. O-ring Removing and installing, see «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) Always replace Coat with clean engine oil
7. Fuel injectors -N30- through -N33-, Cylinder 5/6 Fuel Injector -N83-, - N84- Removing and installing, see «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq)
8. Retaining clip Make sure clip is correctly seated on fuel injector and fuel rail

Identifying Fuel Rail With Fuel Injectors. Scheme 442

Scheme 443

1. Remove engine cover (arrows). (Scheme 443): Removing Engine Cover
2. Remove intake air hose between Mass Air Flow (MAF) sensor and intake air elbow.
3. Remove all harness connectors to injectors.
4. Disconnect vacuum hose from fuel pressure regulator.
5. Expose wires at fuel distributor.
6. Unscrew fuel distributor from intake manifold (arrows).
7. Remove fuel distributor with injectors from intake manifold simultaneously upward and set aside in rear of engine compartment on a clean cloth. (Scheme 444): Unscrewing Fuel Distributor From Intake Manifold WARNING: Fuel system is under pressure! Place a cloth around the connection point before opening system. Then release pressure by carefully loosening connection point.
8. Disengage retaining clip and remove fuel injector.

Note. Fuel lines must be disconnected before replacing fuel distributor.

Installation is reverse of removal, noting the following

1. Remove O-rings at all opened connections. (Never remove plastic cap from valve head to replace front O-ring - pry O-ring off over plastic cap).
2. Lightly lubricate O -rings with clean engine oil.
3. Make sure fuel injectors are in place and seated correctly
4. Check clip for unobstructed installing.
5. Place fuel rail with secured fuel injectors onto intake manifold, and apply uniform pressure to press it in.

Tightening torque

TIGHTENING TORQUE: FUEL DISTRIBUTOR

Scheme 444

1. VAG1348/3A with VAG1348/3 -2
2. VAG1594A
3. VAG1598/31
4. VAG1602
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B (Scheme 445): Identifying Special Tools And Equipment

Test requirement

1. Fuel pressure OK: checking, see «FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__fuel-pressure-regulator-and-residual-pressure) .

1. Remove fuel distributor including fuel injectors from intake manifold. See «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Fuel lines remain connected.
2. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
3. Bridge terminals 1 and 65 at test box using adapter cables from VAG1594A connector test kit (this step supplies Ground -GND- to one side of relay coil for Fuel Pump -FPrelay).

Note. Fuel Pump (FP) relay is supplied with B+ via the central electric (terminal 30). Fuel Pump (FP) relay receives minus via the cable bridge in test box. The Fuel Pump (FP) is now running constantly.

Checking Proper Seal

1. Check proper seal of fuel injectors (visual inspection). With Fuel Pump (FP) running, only 1 to 2 drops per minute may drip out per injector.
2. If fuel loss is greater, stop Fuel Pump (FP) from running (disconnect cable bridge) and replace faulty fuel injector. See «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Scheme 445

Scheme 446

1. Insert fuel injector to be tested in a measuring glass from VAG1602 injection quantity test device. (Scheme 446): Inserting Fuel Injector To Be Tested In Measuring Glass
2. Connect one terminal of fuel injector to engine Ground (GND) using an adapter cable and an alligator clip from VAG1594A connector test kit.
3. Connect second terminal of fuel injector to B+ using VAG1348/3A remote control, VAG1348/3 -2 adapter cable and assisting cable. (Scheme 447): Connecting One Terminal Of Fuel Injector To Engine Ground Using VAG1348/3A Remote Control
4. Bridge terminals 1 and 65 at test box using wires from VAG1594A adapter test kit. Fuel Pump (FP) must run.
5. Operate VAG1348/3A remote control for 30 seconds.
6. After all three fuel injectors of one cylinder row have been activated, place measuring glasses on an even surface. Specified value for each fuel injector: 90 to 125 ml.
7. If measured value of one or more fuel injectors is outside of specified range, switch Fuel Pump (FP) off (disconnect cable bridge) and replace faulty fuel injector. See «FUEL INJECTORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq).
8. Repeat test at fuel injectors of second cylinder row.
9. If measured values of all fuel injectors are outside specified range, check fuel pressure. See «FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__fuel-pressure-regulator-and-residual-pressure). NOTE: Also check spray pattern when checking injection quantity. Spray pattern must be the same for all injectors
10. Install fuel injectors together with fuel distributor. See «TIGHTENING TORQUE»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__tightening-torque).

Scheme 447

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAS5051 with VAG5051/1 or
5. VAG1551 with VAG1551/3B see scheme 54: Identifying Special Tools And Equipment

Voltage supply

Voltage is supplied to the Fuel Pump (FP) and several components of the injection system via the Fuel Pump (FP) relay -J17-.

Engine must be turning for Fuel Pump (FP) relay -J17- to close. This means that the relay does not receive Ground (via ECM) until the ECM recognizes RPM signals.

Note. Fuel Pump (FP) relay is located at position 4 of central electrics in driver's footwell, left.

Identifying Fuel Pump (FP) Relay. Scheme 448

1. Battery voltage at least 12.7 V

1. Remove driver-side storage compartment. See «DRIVER'S STORAGE COMPARTMENT, REMOVING»(/audi/a6/c5-1997-2001/remont/mirrors/#interior-equipment__drivers-storage-compartment-removing).
2. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq). Ignition must remain switched on for this.
3. Initiate output Diagnostic Test Mode and activate Evaporative Emission (EVAP) canister purge regulator valve -N80-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function). Fuel Pump (FP) relay (at position 4 of central electrics in driver's footwell, left) must trigger and Fuel Pump (FP) must run. (Scheme 449): Identifying Fuel Pump (FP) Relay

1. If relay does not trigger: Check voltage supply of Fuel Pump (FP) relay. See «CHECK VOLTAGE SUPPLY OF FUEL PUMP (FP) RELAY»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Checking activation of Fuel Pump (FP) relay. See «CHECK VOLTAGE SUPPLY OF FUEL PUMP (FP) RELAY»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. If relay triggers, but Fuel Pump (FP) does not run: Check voltage supply for Fuel Pump (FP) and components (via Fuel Pump -FP- relay). See «CHECK VOLTAGE SUPPLY FOR FUEL PUMP (FP) AND COMPONENTS»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Scheme 449

1. Remove Fuel Pump (FP) relay.
2. Connect multimeter to terminal 17 of relay socket and Ground (GND) for voltage measurement. (Scheme 450): Identifying Fuel Pump (FP) Relay Terminal 17 In Relay Carrier Specification: approx. battery voltage

If specified value is not obtained

1. Replace central electrics.

Scheme 450

1. Switch ignition off.
2. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831).
3. Bridge terminals 1 and 65 at test box using wires from VAG1594A adapter test kit. Fuel Pump (FP) relay (at position 4 of central electrics in driver's footwell, left) must trigger. (Scheme 451): Identifying Fuel Pump (FP) Relay

If relay triggers now, but did not during output DTM

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

If relay does not trigger

Scheme 451

1. Remove cable bridge.
2. Remove Fuel Pump (FP) relay.
3. Connect multimeter to terminal 19 of relay socket and Ground (GND) for voltage measurement. see scheme 59: Identifying Fuel Pump Relay Terminal 19 In Relay Socket Specification: approx. battery voltage

If specified value is not obtained

1. Check wire connections.

If specified value is obtained

Identifying Fuel Pump (FP) Relay Terminals. Scheme 452

1. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: FUEL PUMP RELAY CIRCUIT DIAGNOSIS: TERMINAL 16 Central electric in driver-side footwell, left, position 4 Terminal VAG1598/31 test box Socket 16 65
2. Repair open circuit or short circuit if necessary.

If no malfunctions are detected

1. Replace Fuel Pump (FP) relay -J17-.
2. Re-connect Engine Control Module (ECM).

Locating Fuses S228, S229, And S234 In Fuse Holder. Scheme 453

1. Remove fuses S228, S229, and S234 (positions 28, 29, and S234) from fuse holder.
2. Initiate output Diagnostic Test Mode. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function) . And activate Evaporative Emission (EVAP) canister purge regulator valve -N80-.
3. Connect multimeter for voltage measurement to Ground (GND) and to one terminal of following fuses in fuse holder. FUSE VOLTAGE SPECIFICATIONS Fuse Specified value at one of the terminals S228 approx. battery voltage S229 approx. battery voltage S234 approx. battery voltage

If specified values are not obtained

1. Repeat test at another terminal of fuse socket.

If specified values are not obtained again

1. Check wire connections.

If no malfunctions are detected

1. Replace Fuel Pump (FP) relay -J17-.
2. Re-insert fuses.

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAS5051 with VAG5051/1 or
5. VAG1551 with VAG1551/3B see scheme 62: Identifying Special Tools And Equipment

1. Coolant Temperature at least 80 °C.
2. Electrical consumers switched off (coolant fan must NOT run during test).
3. A/C switched off.
4. Fuse for Mass Air Flow (MAF) sensor OK

Checking function

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Mass Air Flow (MAF) Sensor (1 Of 4). Scheme 454

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

Note. During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

When indicated on display

Identifying Scan Tool Display - Checking Mass Air Flow (MAF) Sensor (2 Of 4). Scheme 455

1. Press buttons -0-, -0- and -2- to select "display group number 002" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Mass Air Flow (MAF) Sensor (3 Of 4). Scheme 456

1. Check specified values for load detection in display fields 3 and 4. DISPLAY GROUP 002: AIR MASS TAKEN IN WITH ENGINE AT IDLE AND OPERATING TEMPERATURE Display fields 1 2 3 4 Display group 002: Air mass taken in with engine at idle and operating temperature Display xxx /min xx.x% x.x ms xxx.x g/s Indicated Engine speed (RPM) Load mean injection time Air mass Functional range 0 to 6800 RPM 12 to 100% 1.0 to 20.0 ms 1.0 to 150 g/s Specified value 720 to 820 RPM (1) 670 to 770 RPM (2) 12.0 to 26.0% 1.0 to 4.0 ms 1.0 to 5.0 g/s Notes - - If specified value is not obtained: Evaluation display field 3, see «EVALUATION DISPLAY GROUP 002»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . If specified value is not obtained: Evaluation display field 4, see see «EVALUATION DISPLAY GROUP 002»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . (1) Front Wheel Drive Vehicles (2) All-Wheel Drive Vehicles

If specified values are obtained

1. Press --> button.

Indicated on display (function selection)

Identifying Scan Tool Display - Checking Mass Air Flow (MAF) Sensor (4 Of 4). Scheme 457

Evaluation display group 002

EVALUATION DISPLAY GROUP 002

Evaluation display group 002

EVALUATION DISPLAY GROUP 002

1. Disconnect connector from Mass Air Flow (MAF) sensor. (Scheme 458): Identifying MAF Sensor Harness Connector Terminals
2. Connect multimeter for voltage measurement as follows. MAF SENSOR CIRCUIT TEST: TERMINAL 3 Harness connector Terminal Measure to 3 Engine Ground (GND)
3. Operate starter briefly. Specification: approx. battery voltage

Note. Voltage is supplied to Mass Air Flow (MAF) sensor from Fuel Pump (FP) relay.

If specified value is not obtained

Scheme 458

1. Check wire connection from terminal 3 of connector to Fuel Pump (FP) relay via fuse for open circuit and short circuit to Ground (GND)
2. Repair open circuit or short circuit if necessary. (Scheme 459): Identifying MAF Sensor Harness Connector Terminals
3. Connect multimeter to terminal 2 and terminal 3 of connector for voltage measurement.
4. Operate starter briefly. Specification: approx. battery voltage

Note. Ground (GND) from the ECM is present at terminal 2 of connector.

If specified value is not obtained

Scheme 459

1. Check wire connections. See «CHECK WIRE CONNECTIONS FOR MASS AIR FLOW (MAF) SENSOR»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-wire-connections-for-mass-air). (Scheme 460): Identifying MAF Sensor Harness Connector Terminals
2. Connect multimeter to terminal 1 and terminal 2 of connector for voltage measurement.
3. Switch ignition on. Specification: about 5 V

If specified value is not obtained

1. Check wire connections. See «CHECK WIRE CONNECTIONS FOR MASS AIR FLOW (MAF) SENSOR»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-wire-connections-for-mass-air) .

Check wire connections for Mass Air Flow (MAF) sensor

Note. Signal wire is also checked during wire test.

Scheme 460

1. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 70: Identifying MAF Sensor Harness Connector Terminals
2. Check following wire connections for open circuit and short circuit to Ground (GND) and B+: MAF SENSOR CIRCUIT TEST: TERMINALS 1, 2, 4 Harness connector Terminal VAG1598/31 test box Socket 1 53 2 27 4 29
3. Repair open circuit or short circuit if necessary.
4. Also check all wires for short circuit to each other.

If wire connection is OK

1. Replace Mass Air Flow (MAF) sensor -G70-.

Special tools and equipment

1. VAS5051 with VAG5051/1 or
2. VAG1551 with VAG1551/3B
3. Engine leak detection spray G 001 800 A1

Identifying Special Tools And Equipment. Scheme 461

1. The negative pressure in the intake system sucks in the leak detection spray with the unmetered air. Leak detection spray decreases ignition quality and performance of the fuel mixture. This causes a reduction in engine speed and a sharp increase of CO content.
2. It is absolutely necessary to follow the safety precautions listed on the can.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Intake Air System (1 Of 4). Scheme 462

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

When indicated on display

Identifying Scan Tool Display - Checking Intake Air System (2 Of 4). Scheme 463

1. Press buttons -0-, -0- and -1- to select "display group number 001" and press -Q- button to confirm input.

Indicated on display: (1 thru 4 = display fields)

Identifying Scan Tool Display - Checking Intake Air System (3 Of 4). Scheme 464

1. Make note of engine speed in display field 1.
2. Spray intake system parts with engine leak detection spray in a systematic manner.

If engine speed does not change

1. Press right arrow button.

Indicated on display (function selection)

Identifying Scan Tool Display - Checking Intake Air System (4 Of 4). Scheme 465

If engine speed decreases

1. Press right arrow button.
2. Press buttons -0- and -6- to select "End output" and press -Q- button to confirm input.
3. Switch ignition off.
4. Check sprayed part of intake system for leaks, and eliminate error.

Intake manifold change-over

This test should only be performed if there is a performance deficiency.

The intake manifold switches from the long intake path to the short one at approx. 4700 RPM.

Intake manifold change-over function, checking

1. Increase engine RPM significantly above 4700 RPM. This process should actuate vacuum diaphragm for intake manifold change-over. (Component location: on intake manifold front left, beneath ignition coils).

If the change -over does not occur, the following tests must be performed.

1. Check Intake Manifold Change -Over Valve -N156-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function) . If necessary, check activation valve. See «INTAKE MANIFOLD CHANGE-OVER VALVE -N156-, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) or «CHECKING ACTIVATION»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) ).
2. Check vacuum system for proper seal. See «VACUUM SYSTEM, CHECKING FOR PROPER SEAL»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
3. Check vacuum lines for proper connection, sealing and continuity.
4. Check whether change-over mechanism moves easily (operate change -over linkage by hand).

1. VAG1348/3-2
2. VAG1348/3A
3. VAG1390
4. VAG1594A (Scheme 466): Identifying Special Tools And Equipment

Scheme 466

1. Let vehicle run at idle for 2 to 3 minutes (vacuum build-up).
2. Switch ignition off.
3. Disconnect connector from Intake Manifold Change-Over Valve -N156-.
4. Connect one terminal of solenoid valve to engine Ground (GND) using an adapter cable and an alligator clip from VAG1594A connector test kit.
5. Connect second terminal of solenoid valve to B+ using VAG1348/3A remote control, VAG1348/3 -2 adapter cable and assisting cable. (Scheme 467): Connecting One Terminal Of Intake Manifold Change-Over Solenoid Valve To Engine Ground Using VAG1348/3A Remote Control
6. Operate VAG1348/3A remote control for approx. 2 to 3 minutes. Vacuum diaphragm must remain activated during this time.

If the vacuum diaphragm moves back, check vacuum reservoir as follows

Scheme 467

1. Disconnect vacuum hoses from vacuum reservoir for intake manifold change-over.
2. Connect VAG1390 hand vacuum pump to vacuum reservoir.
3. Operate hand vacuum pump and observe change-over procedure.
4. Check vacuum reservoir for proper seal. (Vacuum reservoir must not return to rest position, as long as hand vacuum pump is not vented.)
5. Replace vacuum reservoir if necessary.
6. If vacuum diaphragm does not activate, check Intake Manifold Change -Over Valve -N156- for continuity as follows
7. Connect one terminal of Intake Manifold Change-Over Valve -N156- to engine Ground (GND) using an adapter cable and an alligator clip from VAG1594A connector test kit. (Scheme 468): Connecting One Terminal Of Intake Manifold Change-Over Valve -N156- To Engine Ground Using VAG1348/3A Remote Control
8. Connect second terminal of Intake Manifold Change -Over Valve - N156- to B+ using VAG1348/3A remote control, VAG1348/3 -2 adapter cable and assisting cable.
9. Operate VAG1348/3A remote control.
10. Check valve for throughput (disconnect vacuum hose and blow through).
11. If necessary, replace intake manifold change-over valve.
12. Check vacuum system for leaks if no malfunctions were detected for all previous tests.

Scheme 468

1. VAG1526A
2. VAG1527B
3. VAG1594A
4. VAG1598/31
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B (Scheme 469): Identifying Special Tools And Equipment

Component location

See COMPONENT LOCATIONS, OVERVIEW .

1. Output Diagnostic Test Mode (DTM) performed
2. Fuse for intake manifold change -over valve is OK
3. Fuel Pump (FP) OK: checking, see «FUEL PUMP (FP) RELAY -J17- AND ACTIVATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Scheme 469

1. Disconnect connector from Intake Manifold Change-Over Valve -N156-. (Scheme 470): Checking Intake Manifold Change-Over Valve -N156- Resistance
2. Connect multimeter at valve for resistance measurement. Specification: 25 to 35 ohms
3. Replace Intake Manifold Change -Over Valve -N156- if specified value is not obtained.

Scheme 470

1. Disconnect connector from Intake Manifold Change -Over Valve -N156-. (Scheme 471): Identifying Intake Manifold Change-Over Valve Harness Connector Terminals
2. Connect VAG1527B voltage tester as follows: INTAKE MANIFOLD CHANGE-OVER VALVE CIRCUIT TEST: TERMINAL 1 Harness Connector Terminal Measure To 1 Engine Ground (GND)
3. Operate starter briefly. LED must light up.

If LED does not light up

1. Check wire connection from terminal 1 to Fuel Pump (FP) relay via fuse for open circuit.

Checking activation

1. Connect VAG1527B voltage tester between terminals 1 and 2
2. Initiate output Diagnostic Test Mode. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function) and activate intake manifold change -over valve. LED must blink.

If LED does not blink or if it remains constantly lit

Scheme 471

1. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 83: Identifying Intake Manifold Change-Over Valve Harness Connector Terminals
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: INTAKE MANIFOLD CHANGE-OVER VALVE CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 104
3. Repair open circuit or short circuit if necessary.

If wire connection is OK

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Oxygen sensor control, function

The oxygen sensors compare the oxygen content of the air with residual oxygen content in exhaust and deliver a voltage signal to the control module. The voltage signal "mixture rich (too little residual oxygen)" is approx. 0.7 to 1.0 V. The voltage signal "mixture lean (a lot of residual oxygen)" is approx. +0.0 to 0.3 V. At the transition from "rich" to "lean" and vice-versa (LEMDA = 1.0) voltage will jump from 0.7 to 1.0 V to 0.0 to +0.3 V (or vice versa). Due to the steep voltage jump, oxygen sensor control cannot maintain the ideal mixture of LEMDA = 1.0 as constant. Oxygen sensor control constantly fluctuates back and forth between the conditions "slightly too lean" and "slightly too rich".

If voltage change does not occur or occurs only slowly, the following malfunctions could be present

1. Slits or holes in sensor head clogged.
2. Sensors suffered thermal overload.
3. Transition resistance in signal wire or Ground (GND) wire.
4. Sensor too cold, sensor heating not functioning.
5. Sensor damaged by contact spray or similar substance (contact spray is drawn through the fine hollow interiors by thermal fluctuations and capillary action into the electrical wiring in sensor).
6. Sensor damaged by silicon vapors (the use of sealants containing silicon leads to trace elements of silicon being taken in by the engine. These silicon elements are not combusted and damage the oxygen sensor).

Scheme 472

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAS5051 with VAG5051/1 or
5. VAG1551 with VAG1551/3B see scheme 84: Identifying Special Tools And Equipment

Note. For the defined troubleshooting procedure, it is possible, to switch oxygen sensor control off by selecting display group 099 under "basic setting" and switch it on again under "read measuring value block". After selecting display group 099 (either in "basic setting" or "read measuring value block"), it is possible to switch back and forth between "basic setting" (function 04) and "read measuring value block" (function 08) by pressing buttons 4 or 8 on the VAG1551. Once function 04 "basic setting" is exited, oxygen sensor control is automatically switched on again.

1. Road test performed and DTC memory erased.
2. Coolant temperature at least 80 °C Display group 4, display field 3

Function test

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensors And Oxygen Sensor Control Before Catalytic Converter (1 Of 3). Scheme 473

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

Note. During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensors And Oxygen Sensor Control Before Catalytic Converter (2 Of 3). Scheme 474

1. Press buttons -0-, -3- and -0- to select "display group number 030" and press -Q- button to confirm input.

When indicated on display

1. Check oxygen sensor status in display fields 1 and 3.

Note. "Oxygen sensor status" indicates status of oxygen sensor control and oxygen sensors.

DISPLAY GROUP 030: OXYGEN SENSOR STATUS WITH ENGINE AT IDLE

Significance of 3 digit indication of display group 030

SIGNIFICANCE OF 3 DIGIT INDICATION OF DISPLAY GROUP 030

Note. The oxygen sensor control of the oxygen sensors behind catalytic converter (B1 -S2 and B2-S2) are not active at certain operation points without engine load, that means that the third position of the oxygen sensor controls behind catalytic converter can fluctuate between 0 and 1. The first position of the 3 digit indication (heating) fluctuates between 0 and 1 at certain operation points.

Checking oxygen sensor adaptation values and control

1. Press -C- button.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Adaptation Values And Control (1 Of 3). Scheme 475

1. Press buttons -0-, -3- and -3- to select "display group number 033" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Adaptation Values And Control (2 Of 3). Scheme 476

1. Check oxygen sensor control in display fields 1 and 3. DISPLAY GROUP 033: OXYGEN SENSOR CONTROL BEFORE CATALYTIC CONVERTER 1 2 3 4 Display group 033: Oxygen sensor control before catalytic converter Display xx.x% x.xxx volts xx.x% x.xxx V Indicated Oxygen sensor control Bank 1 Oxygen sensor voltage Bank 1 Oxygen sensor control Bank 2 Oxygen sensor voltage Bank 2 Functional range -25.0 to 25.0% 0.100 to 1.000 V -25.0 to 25.0% 0.100 to 1.000 V Specified value Value must fluctuate by at least 2% in the range 10.0 to 10.0% Value must fluctuate approx. 0.3 V in the range 0.100 to 1.000 volts Value must fluctuate by at least 2% in the range 10.0 to 10.0% Value must fluctuate approx. 0.3 V in the range 0.100 to 1.000 volts Notes If specified value is not obtained , go to «EVALUATION DISPLAY GROUP 033»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . If specified value is not obtained , go to «EVALUATION DISPLAY GROUP 033»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Evaluation display group 033 EVALUATION DISPLAY GROUP 033 Display field: 1/3 Possible cause Corrective action Values in range: -10.0 to -25.0% or Values in range: 10.0 to 25.0% or Value does not fluctuate by at least 2% Oxygen sensor heating faulty Check oxygen sensor heating . See «OXYGEN SENSOR HEATING FOR OXYGEN SENSORS BEFORE AND BEHIND CATALYTIC CONVERTER, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Open circuit in wires between oxygen sensor and control module Short circuit to Ground (GND) or B+ between oxygen sensor and control module Check primary voltage. See «CHECKING PRIMARY VOLTAGE»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__checking-primary-voltage) . Check oxygen sensor wires bank 1. See «CHECK OXYGEN SENSOR WIRES BANK 1 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G39»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-bank-1) . Check oxygen sensor wires bank 2. See «CHECK OXYGEN SENSOR WIRES BANK 2 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G108»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-bank-2) . False air in intake area Fuel pressure too low or too high Check intake system for leaks and repair false air. See «INTAKE AIR SYSTEM, CHECKING FOR LEAKS (UNMETERED AIR)»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Check fuel pressure regulator. See «FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__fuel-pressure-regulator-and-residual-pressure) . Fuel return line is kinked or clogged Check fuel return line.
2. Press -C- button.
3. Press buttons -0-, -3- and -2- to select "display group number 032" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Adaptation Values And Control (3 Of 3). Scheme 477

1. Check oxygen sensor control in display fields 1 to 4: DISPLAY GROUP 032: OXYGEN SENSOR ADAPTATION VALUES BEFORE CATALYTIC CONVERTER Display fields 1 2 3 4 Display group 032: Oxygen sensor adaptation values before catalytic converter Display xx.x% xx.x% xx.x% xx.x% Indicated Oxygen sensor adaptation value Bank 1 at idle (additive) Oxygen sensor adaptation value Bank 1 at partial throttle (multiple) Oxygen sensor adaptation value Bank 2 at idle (additive) Oxygen sensor adaptation value bank 2 at partial throttle (multiple) Functional range -25.0 to 25.0% -25.0 to 25.0% -25.0 to 25.0% -25.0 to 25.0% Specified value -10.0 to 10.0% can fluctuate slightly -10.0 to 10.0% can fluctuate slightly -10.0 to 10.0% can fluctuate slightly -10.0 to 10.0% can fluctuate slightly Notes If specified value is not obtained , go to «EVALUATION DISPLAY GROUP 032»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Evaluation display group 032

EVALUATION DISPLAY GROUP 032

Evaluation display group 032

EVALUATION DISPLAY GROUP 032

Checking primary voltage

Component location of harness connectors. See COMPONENT LOCATIONS, OVERVIEW , Overview of component locations.

Note. Coolant reservoir screws must be removed and coolant reservoir must be placed to side in order to access this harness connector. The coolant hoses can remain connected.

1. Fuse for oxygen sensor are OK

1. Disconnect 4-pin harness connector leading to respective oxygen sensor. (Scheme 478): Identifying HO2S 4-Pin Harness Connector Terminals
2. Connect multimeter between terminal 3 and 4 for voltage measurement.
3. Switch ignition on. Specification: 0.400 to 0.500 V
4. Switch ignition off.

If specified value is not obtained

1. Check oxygen sensor wires. See «CHECK OXYGEN SENSOR WIRES BANK 1 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G39»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-bank-1) or «CHECK OXYGEN SENSOR WIRES BANK 2 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G108»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-bank-2) .

Check oxygen sensor wires bank 1 for Heated Oxygen Sensor (HO2S) 2 -G39-.

Component location of harness connectors. See COMPONENT LOCATIONS, OVERVIEW .

1. Disconnect black 4-pin harness connector to bank 1 Heated Oxygen Sensor (HO2S) -G39-.
2. Connect VAG1598/31 test box at wiring harness to ECM, do NOT connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 92: Identifying HO2S 4-Pin Harness Connector Terminals
3. Check following wire connections for open circuit. HO2S (BANK 1, -G39-) CIRCUIT TEST: TERMINALS 3 & 4 Harness connector Terminal VAG1598/31 test box Socket 3 51 4 70
4. Repair open circuit if necessary.
5. Check wires to each other for short circuit. HO2S (BANK 1, -G39-) CIRCUIT TEST: TERMINAL 4 Harness connector Terminal VAG1598/31 test box Socket 4 51 (Scheme 480): Identifying HO2S 4-Pin Harness Connector Terminals
6. Check shielded wire for short circuit to sensor wires. HO2S (BANK 1, -G39-) CIRCUIT TEST: TERMINALS 3 & 4 (SHIELDED WIRE) Harness connector Terminal VAG1598/31 test box Socket 3 32 4 32

If no malfunctions are found in wires

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Check oxygen sensor wires bank 2 for Heated Oxygen Sensor (HO2S) 2 -G108-.

Component location of harness connectors. See COMPONENT LOCATIONS, OVERVIEW .

Scheme 478

1. Disconnect black 4-pin harness connector to bank 2 Heated Oxygen Sensor (HO2S) 2 -G108-.
2. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 94: Identifying HO2S 4-Pin Harness Connector Terminals
3. Check following wire connections for open circuit. HO2S (BANK 2, -G108-) CIRCUIT TEST: TERMINALS 3 & 4 Harness connector Terminal VAG1598/31 test box Socket 3 12 4 13
4. Repair open circuit if necessary.
5. Check wires to each other for short circuit. HO2S (BANK 2, -G108-) CIRCUIT TEST: TERMINAL 4 Harness connector Terminal VAG1598/31 test box Socket 4 12
6. Check shielded wire for short circuit to sensor wires. HO2S (BANK 2, -G108-) CIRCUIT TEST: TERMINALS 3 & 4 (SHIELDED WIRE) Harness connector Terminal VAG1598/31 test box Socket 3 32 4 32

If no malfunctions are found in wires

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Identifying VAG1788/10 RPM Adjuster. Scheme 479

Scheme 480

1. VAG1788/10 RPM adjuster see scheme 96: Identifying VAS5051 With VAG5051/1
2. VAS5051 with VAG5051/1 or
3. VAG1551 with VAG1551/3B

1. Coolant temperature at least 80 °C Display group 4, display field 3

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Aging (Oxygen Sensor Before Catalytic Converter) (1 Of 5). Scheme 481

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Aging (Oxygen Sensor Before Catalytic Converter) (2 Of 5). Scheme 482

1. Press buttons -0-, -3- and -4- to select "display group number 034" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Aging (Oxygen Sensor Before Catalytic Converter) (3 Of 5). Scheme 483

1. Use VAG1788/10 RPM adjuster to adjust engine speed to between 1000 and 2400 RPM.
2. Check specified value in display field 4 after indication "Test ON" appears

Note. This process can take a few minutes.

DISPLAY GROUP 034: OXYGEN SENSOR AGING DIAGNOSTIC, OXYGEN SENSOR BEFORE CATALYTIC CONVERTER (BANK 1)

Note for display field 2

Calculated value from engine speed and engine load .

Note for display fields 3 and 4

Period duration is the time between two oxygen sensor voltage jumps (e.g. rich - lean - rich) and is therefore a measurement of the aging condition of the oxygen sensor. If the specified time is exceeded, display field 4 will indicate = B1 -S1 not OK .

1. Press -C- button.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Aging (Oxygen Sensor Before Catalytic Converter) (4 Of 5). Scheme 484

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

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Aging (Oxygen Sensor Before Catalytic Converter) (5 Of 5). Scheme 485

1. Check specified value in display field 4.

Note. The test in display group 035 is activated simultaneously with the test in display group 034. Therefore the test result is indicated immediately after display group 035 is selected.

DISPLAY GROUP 035: OXYGEN SENSOR AGING DIAGNOSTIC, OXYGEN SENSOR BEFORE CATALYTIC CONVERTER (BANK 2)

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAG1788/10 RPM adjuster
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B see scheme 102: Identifying Special Tools And Equipment

Note. The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It serves as a corrective control. see scheme 103: Oxygen Sensor Graph It corrects slight changes in the mixture (i.e. enrichment) via the oxygen sensor before catalytic converter by holding oxygen sensor control before catalytic converter at its higher or lower point for a specific time (dwell time). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich- direction. If it is in the negative range (i.e.-- 50 ms), mixture is shifted in the -lean- direction.

1. Road test performed and DTC memory erased.
2. Coolant temperature at least 80 °C Display group 4, display field 3

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (1 Of 8). Scheme 486

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

Note. During basic setting, the Evaporative Emission (EVAP) canister purge regulator valve (EVAP valve -N80-) is closed and the A/C compressor is switched off

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (2 Of 8). Scheme 487

1. Press buttons -0-, -3- and -4- to select "display group number 034" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (3 Of 8). Scheme 488

1. Use VAG1788/10 RPM adjuster to adjust engine speed to between 2800 and 3200 RPM.
2. Continue test as soon as display field 2 indicates an exhaust temperature of more than 380 °C NOTE: This process can take a few minutes.
3. Press -C- button.
4. Let engine continue to idle

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (4 Of 8). Scheme 489

1. Press buttons -0-, -3- and -0- to select "display group number 030" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (5 Of 8). Scheme 490

1. Check oxygen sensor status for oxygen sensor behind catalytic converter in display fields 2 and 4.

Note. "Oxygen sensor status" indicates status of oxygen sensor control and oxygen sensors.

DISPLAY GROUP 030: OXYGEN SENSOR STATUS WITH ENGINE AT IDLE

Note. Oxygen sensor control of oxygen sensor behind catalytic converter (bank 1 sensor 2 and bank 2 sensor 2) are not active without engine load, meaning that the display is 0. The first position of the 3 digit indication (heating) fluctuates between 0 and 1. The third position of the 3 digit indication (oxygen sensor control) fluctuates between 0 and 1.

Significance of 3 digit indication of display group 030

SIGNIFICANCE OF 3 DIGIT INDICATION OF DISPLAY GROUP 030

1. Press -C- button.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (6 Of 8). Scheme 491

1. Press buttons -0-, -4- and -3- to select "display group number 043" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (7 Of 8). Scheme 492

1. Check specified value in display field 4 after indication "Test ON" appears

DISPLAY GROUP 043: OXYGEN SENSOR AGING, OXYGEN SENSOR BEHIND CATALYTIC CONVERTER (BANK 1)

If specified value B1 -S2 "OK" is obtained

1. Press -C- button.
2. Press buttons -0-, -4- and -4- to select "display group number 044" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (8 Of 8). Scheme 493

1. Check specified value in display field 4 after indication "Test ON" appears

DISPLAY GROUP 044: OXYGEN SENSOR AGING, OXYGEN SENSOR BEHIND CATALYTIC CONVERTER (BANK 2)

If specified value B2 -S2 "OK" is obtained

1. Press -C- button.

Checking oxygen sensor control behind catalytic converter

1. Perform a test drive of approx. 10 minutes. WARNING: Observe safety precautions to reduce the risk of accidents during road test. See «MULTIPORT FUEL INJECTION (MFI)»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. Let engine continue to run at idle.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (1 Of 3). Scheme 494

1. Press buttons -0-, -3- and -7- to select "display group number 037" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (2 Of 3). Scheme 495

1. Check oxygen sensor voltage in display field 2.
2. Check dwell time between oxygen sensor 1 before catalytic converter and oxygen sensor 2 behind catalytic converter in display field 3 and diagnostic result in display field 4.

DISPLAY GROUP 037: DIAGNOSTIC, OXYGEN SENSOR CONTROL SYSTEM (BANK 1)

Note for display field 3

The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It corrects slight changes in the mixture (i.e. toward rich or lean) due to the oxygen sensor before catalytic converter by holding oxygen sensor control before catalytic converter at its higher or lower point for a specific time (dwell time). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich - direction. If this time is in the negative range (i.e. -50 ms), mixture is shifted in the -lean- direction .

1. Press -C- button.
2. Press buttons -0-, -3- and -8- to select "display group number 038" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor And Oxygen Sensor Control Behind Catalytic Converter (3 Of 3). Scheme 496

1. Check specified value in display field 4.

Note. The test in display group 038 is activated simultaneously with the test in display group 037 Therefore the test result is indicated immediately after display group 038 is selected.

DISPLAY GROUP 038: DIAGNOSTIC OF OXYGEN SENSOR CONTROL SYSTEM (BANK 2)

Note for display field 3

The oxygen sensor control behind catalytic converter overrules the oxygen sensor control before catalytic converter. It corrects slight changes in the mixture (i.e. toward rich or lean) due to the oxygen sensor before catalytic converter by holding oxygen sensor control before catalytic converter at its higher or lower point for a specific time (dwell time). If this time is in the positive range (i.e. 50 ms), mixture is shifted in the -enrich - direction. If this time is in the negative range (i.e. -50 ms), mixture is shifted in the -lean- direction .

Evaluation of display group 037 and 038

EVALUATION OF DISPLAY GROUP 037 AND 038

If specified value in display group 037 and 038 display field 3 or 4 is not obtained

1. Search for leaking air at exhaust system or catalytic converter (check screw clamps and exhaust system for damage).
2. Check if possibly oxygen sensors behind catalytic converter of cylinder bank 1 and 2 have been switched, in case of extremely different values (e.g. +500 ms, - 500 ms) of display fields 3 (oxygen sensor correction value) in measuring value blocks 037 and 038.

If none of the listed causes applies

1. Replace respective oxygen sensor -before - catalytic converter

For component location of harness connectors, see COMPONENT LOCATIONS, OVERVIEW .

1. Disconnect 4-pin harness connector leading to respective oxygen sensor. (Scheme 497): Identifying HO2S 4-Pin Harness Connector Terminals
2. Connect multimeter between terminal 3 and 4 for voltage measurement.
3. Switch ignition on. Specification: 0.400 to 0.500 V
4. Switch ignition off.

If specified value is not obtained

1. Check oxygen sensor wires. See «TESTING OXYGEN SENSOR WIRES»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__testing-oxygen-sensor-wires) , Bank 1 or «CHECK OXYGEN SENSOR WIRES FOR OXYGEN SENSOR (O2S) 2 BEHIND THREE WAY CATALYTIC CONVERTER (TWC) -G131-.»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-for-oxygen) , bank 2.

If specified value is obtained

1. Replace appropriate oxygen sensor behind catalytic converter.

Testing Oxygen Sensor Wires

For component location of harness connectors, see COMPONENT LOCATIONS, OVERVIEW .

1. Disconnect green 4 -pin harness connector 1 to Oxygen Sensor (O2S) Behind Three Way Catalytic Converter (TWC) -G130-.
2. Connect VAG1598/31 test box at wiring harness to ECM; do NOT connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). (Scheme 498): Identifying HO2S 4-Pin Harness Connector Terminals
3. Check following wire connections for open circuit. HO2S CIRCUIT TEST: TERMINALS 3 & 4 Harness connector Terminal VAG1598/31 test box Socket 3 68 4 69
4. Repair open circuit if necessary.
5. Check wires to each other for short circuit. HO2S CIRCUIT TEST: TERMINAL 4 Harness connector Terminal VAG1598/31 test box Socket 4 68 see scheme 117: Identifying HO2S 4-Pin Harness Connector Terminals
6. Check shielded wire for short circuit to sensor wires. HO2S CIRCUIT TEST: TERMINALS 3 & 4 (SHIELDED WIRE) Harness connector Terminal VAG1598/31 test box Socket 3 32 4 32

If no malfunctions are found in wires

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Check oxygen sensor wires for Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.

For component location of harness connectors, see COMPONENT LOCATIONS, OVERVIEW .

Scheme 497

1. Disconnect brown 4 -pin harness connector 2 to Oxygen Sensor (O2S) 2 Behind Three Way Catalytic Converter (TWC) -G131-.
2. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 118: Identifying HO2S 4-Pin Harness Connector Terminals
3. Check following wire connections for open circuit. HO2S -G131- CIRCUIT TEST: TERMINALS 3 & 4 Harness connector Terminal VAG1598/31 test box Socket 3 10 4 11
4. Repair open circuit if necessary.
5. Check wires to each other for short circuit. HO2S -G131- CIRCUIT TEST: TERMINAL 4 Harness connector Terminal VAG1598/31 test box Socket 4 10 see scheme 119: Identifying HO2S 4-Pin Harness Connector Terminals
6. Check shielded wire for short circuit to sensor wires. HO2S -G131- CIRCUIT TEST: TERMINALS 3 & 4 (SHIELDED WIRE) Harness connector Terminal VAG1598/31 test box Socket 3 32 4 32

If no malfunctions are found in wires

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Scheme 498

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAG1788/10 RPM adjuster
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B see scheme 120: Identifying Special Tools And Equipment

Testing

Note. The heating circuit of the oxygen sensor is monitored by On Board Diagnostic (OBD),. Check DTC memory. See CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05) .

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Heating (1 Of 5). Scheme 499

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

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Heating (2 Of 5). Scheme 500

1. Press buttons -0-, -4- and -1- to select "display group number 041" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Heating (3 Of 5). Scheme 501

1. Check specified values in display fields 1 and 3.

Note. Increasing engine speed accelerates the obtaining of specified values.

DISPLAY GROUP 041: OXYGEN SENSOR HEATING (BANK 1) AT IDLE

Important notes to display fields 1, 2, 3 and 4

1. If oxygen sensors have not yet reached their operating temperature, there will be no indication in display fields 1 and 3, i.e. they will both be empty. (increase engine speed to obtain specified values) .
2. After reaching operating temperature of the two oxygen sensors, a resistance of less than 0.9 kOhm must be indicated in display fields 1 and 3 .
3. Do not continue test until a resistance of less than 0.9 kOhm is indicated in display fields 1 and 3 .
4. At certain points of operation, the ECM "pulses" oxygen sensor heating. This means that oxygen sensor heating is switched on and off at these points. It is entirely possible that the specified value "Htng. bef. Cat. OFF" or "Htng. beh. Cat. OFF" will appear in display fields 2 and 4

1. Press -C- button.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Heating (4 Of 5). Scheme 502

1. Press buttons -0-, -4- and -2- to select "display group number 042" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Oxygen Sensor Heating (5 Of 5). Scheme 503

1. Check specified values in display fields 1 and 3.

DISPLAY GROUP 042: OXYGEN SENSOR HEATING (BANK 2) AT IDLE

Important notes to display fields 1, 2, 3 and 4

1. If oxygen sensors have not yet reached their operating temperature, there will be no indication in display fields 1 and 3, i.e. they will both be empty. (increase engine speed to obtain specified values) .
2. After reaching operating temperature of the two oxygen sensors, a resistance of less than 0.9 kOhm must be indicated in display fields 1 and 3 .
3. Do not continue test until a resistance of less than 0.9 kOhm is indicated in display fields 1 and 3 .
4. At certain points of operation, the ECM "pulses" oxygen sensor heating. This means that oxygen sensor heating is switched on and off at these points. It is entirely possible that the specified value "Htng. bef. Cat. OFF" or "Htng. beh. Cat. OFF" will appear in display fields 2 and 4

If specified value is not obtained

1. Check voltage supply of oxygen sensor heating. See «CHECKING VOLTAGE SUPPLY FOR OXYGEN SENSOR HEATING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .
2. Check oxygen sensor signal wire and activation. See «TESTING OXYGEN SENSOR WIRES»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__testing-oxygen-sensor-wires) or «CHECK OXYGEN SENSOR WIRES FOR OXYGEN SENSOR (O2S) 2 BEHIND THREE WAY CATALYTIC CONVERTER (TWC) -G131-.»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__check-oxygen-sensor-wires-for-oxygen) .

1. Fuse for oxygen sensor heating OK
2. Fuel Pump (FP) OK. For checking, see «FUEL PUMP (FP) RELAY -J17- AND ACTIVATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

For component location of harness connectors, see COMPONENT LOCATIONS, OVERVIEW .

1. Disconnect 4-pin harness connector leading to respective oxygen sensor. see scheme 126: Identifying HO2S 4-Pin Harness Connector Terminals
2. Connect multimeter between terminal 1 and 2 for voltage measurement.
3. Start engine. Specification: approx. battery voltage, possibly fluctuating

Note. At certain operating points, the ECM "pulses" the Ground (GND) for oxygen sensor heating. This means that the Ground (GND) is constantly switched on and off at these points. It is therefore possible that the voltage displayed on the tester will fluctuate. It is possible to observe the ECM switching oxygen sensor heating on and off within the function "read measuring value block", display group numbers 041 and 042.

If there is no voltage

Identifying HO2S Harness Connector Terminals. Scheme 504

1. Connect multimeter for voltage measurement as follows: HO2S HEATER CIRCUIT TEST: TERMINAL 1 Harness connector Terminal Measure to 1 (B+) Vehicle Ground (GND)
2. Operate starter briefly. Specification: approx. battery voltage

If there is no voltage again

1. Check wire connection from terminal 1 to Fuel Pump (FP) relay via fuse for open circuit.

If voltage supply is OK

Identifying HO2S Harness Connector Terminals. Scheme 505

1. Connect multimeter for voltage measurement as follows: HO2S HEATER CIRCUIT TEST: TERMINAL 2 Harness connector Terminal Measure to 2 (Ground -GND- activation of Engine Control Module - ECM-) B+
2. Start engine. Specification: approx. battery voltage, possibly fluctuating
3. Switch ignition off.

If there is no voltage

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). (Scheme 508): Identifying HO2S Harness Connector Terminals
2. Check following wire connection for open circuit: Oxygen Sensor (O2S) heater -Z19- bank 1 before catalytic converter: HO2S -Z19- HEATER CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 5 Oxygen Sensor (O2S) 2 heater -Z28- bank 2 before cat.converter: HO2S -Z28- HEATER CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 4 Oxygen Sensor (O2S) heater 1 -Z29- bank 1 behind cat. converter: HO2S -Z29- HEATER CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 63 Oxygen Sensor (O2S) heater 2 -Z30- bank 2 behind cat. converter: HO2S -Z30- HEATER CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 6

If no malfunctions are found in wires

1. Replace appropriate Oxygen Sensor (O2S).
2. Read readiness code. See «READINESS CODE, CHECKING»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . If DTC memory was erased, readiness code must be re-generated. See «READINESS CODE, GENERATING»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) .

Identifying Special Tools And Equipment. Scheme 506

1. 3337 wrench, 7 -piece set
2. Locking compound G 052 112 A3

For component location of harness connectors, see COMPONENT LOCATIONS, OVERVIEW .

1. Disconnect 4-pin harness connector leading to respective oxygen sensor.
2. Open cable ties.
3. Unscrew oxygen sensor using special tool 3337.

Note the following when installing

Note. Oxygen sensor threads are coated with an assembly paste. This paste must not contact sensor openings. Cable ties must always be installed again in exactly the same place to prevent the sensor wire from contacting the exhaust pipe. Tightening torque: 55 Nm

1. VAG1526A
2. VAG1527B
3. VAG1594A
4. VAG1598/31
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B (Scheme 509): Identifying Special Tools And Equipment

Note. The Evaporative Emission (EVAP) canister purge regulator valve is also called the Tank Ventilation Valve (TVV) and is sometimes referred to as the EVAP valve.

Checking for proper seal

Solenoid valve is closed when no voltage is present.

1. Disconnect hoses from EVAP valve; harness connector remains connected.
2. Attach assisting hose to one connection of EVAP valve.
3. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.
4. Initiate output DTM and activate Evaporative Emission (EVAP) canister purge regulator valve -N80-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function) .

Indicated on display

Identifying Scan Tool Display - Checking Tank Ventilation. Scheme 507

1. Valve must click and must open and close (can be tested by blowing into assisting hose).

If valve does not click

1. Check internal resistance of EVAP valve.

If valve does not open and close properly

1. Replace Evaporative Emission (EVAP) canister purge regulator valve -N80-.

Scheme 508

1. Disconnect connector at EVAP valve.
2. Connect multimeter at valve for resistance measurement. see scheme 133: Checking EVAP Canister Purge Regulator Valve Resistance Specification: 22 to 30 ohms

If specified value is not obtained

1. Replace Evaporative Emission (EVAP) canister purge regulator valve -N80-.

If specified value is obtained

1. Check voltage supply. See «CHECKING VOLTAGE SUPPLY»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

1. Fuse for the EVAP valve OK.
2. Fuel Pump (FP) OK. For checking, see «FUEL PUMP (FP) RELAY -J17- AND ACTIVATION, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Note. Voltage is supplied to the EVAP valve via the Fuel Pump (FP) relay.

1. Disconnect connector at EVAP valve.
2. Connect VAG1527B voltage tester as follows: EVAP CANISTER PURGE REGULATOR VALVE CIRCUIT TEST: TERMINAL 1 Harness connector Terminal Measure to 1 Engine Ground (GND)
3. Operate starter briefly (engine can also start). LED must light up.

If LED does not light up

1. Check wire connection from terminal 1 to Fuel Pump (FP) relay via fuse for open circuit.
2. Repair open circuit if necessary.

If LED lights up

1. Go to «CHECKING ACTIVATION»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

1. Connect VAG1527B voltage tester to connector terminals 1 (B+) and 2. see scheme 135: Identifying EVAP Canister Purge Regulator Valve Harness Connector Terminals
2. Initiate output DTM and activate Evaporative Emission (EVAP) canister purge regulator valve -N80-. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__output-diagnostic-test-mode-dtm-function). LED must blink.

If LED does not blink or if it remains constantly lit

Scheme 509

1. Connect VAG1598/31 test box at wiring harness to ECM; do NOT connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). see scheme 136: Identifying Harness Connector Terminal (3 Of 3)
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: EVAP CANISTER PURGE REGULATOR VALVE CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 64
3. Repair open circuit or short circuit if necessary.

If wire connection is OK

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

EPC system, function

For EPC, the throttle valve is not operated by a cable from the accelerator pedal. There is no mechanical connection between the accelerator pedal and the throttle valve.

The position of the accelerator pedal is communicated to the Engine Control Module (ECM) via two sensors for accelerator pedal position (variable resistances; stored in one housing) that are connected with the accelerator pedal.

The accelerator pedal position (driver's intention) is a main input unit for the ECM.

Operation of the throttle valve occurs via an electric motor (throttle valve actuator) in the throttle valve control module. This is true across the entire engine speed and engine load spectrum.

The throttle valve is operated by the throttle valve actuator according to the instructions of the ECM.

With ignition switched on and engine off, the ECM activates the throttle valve actuator precisely according to the sensor for accelerator pedal position. This means, if the accelerator pedal is depressed half way, the throttle valve actuator opens the throttle valve to the same degree; i.e. throttle valve would be opened half way.

With engine running (under load), the ECM can open or close the throttle valve independently of the sensor for accelerator pedal position.

This means, for example, that the throttle valve could be fully opened even though the accelerator pedal has only been depressed half way. This has the advantage of preventing torque losses at the throttle valve.

In addition to this, it results in significantly better values relative to emissions and consumption under certain load conditions.

It would be incorrect to think that "EPC" consists of only one or two component. EPC is much more of a system containing all components that contribute to recognizing, controlling and monitoring the position of the throttle valve, e.g. sensor for accelerator pedal position, throttle valve control module, EPC warning lamp, Engine Control Module (ECM).

Electronic Power Control (EPC) warning lamp -K132- in instrument cluster, significance

"EPC" is an abbreviation and stands for Electronic Power Control (EPC).

Installation location of EPC warning lamp

Identifying EPC Warning Lamp. Scheme 510

Engine Control Module (ECM) checks all components that are important for function of the EPC system after ignition is switched on.

The Engine Control Module (ECM) switches on the EPC warning lamp after ignition is switched on. Shortly after engine is started, the EPC warning lamp will go out. This requires, first of all, that the Engine Control Module (ECM) does not detect a malfunction in the EPC system and, secondly, that activation of the lamp by the Engine Control Module (ECM) is OK.

If malfunctions are recognized in the EPC system during operation of the engine, the ECM switches on the EPC warning lamp in instrument cluster. (These malfunctions are listed in the DTC table). An entry is made in DTC memory at the same time.

Electronic Power Control (EPC) warning lamp -K132-, checking

Note. The fault light for power accelerator activation -K132- is also called the EPC warning lamp.

Identifying VAG1594A. Scheme 511

Scheme 512

1. VAG1594A (Scheme 517): Identifying VAG1598/31
2. VAG1598/31

Function test of warning lamp

1. Switch ignition on. Engine Control Module (ECM) switches EPC lamp on.
2. Start engine. Shortly after engine is started, the EPC warning lamp will go out if there are not malfunctions stored in DTC memory that relate to the EPC system

1. Electronic Power Control (EPC) warning lamp - K132 - does not light up Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) . Bridge sockets 1 and 48 of test box. Switch ignition on. Warning lamp must light up. If warning lamp does not light up: Switch ignition off. Remove instrument cluster: See «INSTRUMENTS - UP TO 2000»(/audi/a6/c5-1997-2001/remont/gauges-instrument-panels/#instruments-up-to-2000) or «INSTRUMENTS - 2001 AND UP»(ref-196300) . Check following wire connection for open circuit and short circuit to B+: EPC WARNING LAMP CIRCUIT TEST Test box VAG1598/31 Socket Instrument cluster Terminal 48 See SYSTEM WIRING DIAGRAMS. Repair open circuit or short circuit if necessary. If wire connection is OK: Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .
2. Electronic Power Control (EPC) warning lamp - K132 - lights up constantly

1. Check DTC memory of Engine Control Module (ECM).

If no DTCs are stored

1. Connect VAG1598/31 test box at wiring harness to ECM; do NOT connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Remove instrument cluster: See «INSTRUMENTS - UP TO 2000»(/audi/a6/c5-1997-2001/remont/gauges-instrument-panels/#instruments-up-to-2000) or «INSTRUMENTS - 2001 AND UP»(ref-196300) .
3. Check following wire connection for short circuit to Ground (GND): INSTRUMENT CLUSTER TERMINAL CHART Test box VAG1598/31 Socket Instrument cluster Terminal 48 See SYSTEM WIRING DIAGRAMS
4. Repair short circuit if necessary.

If wire connection is OK

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Throttle valve control module -J338 -, checking

The following components are located in the housing for the throttle valve control module

1. Throttle drive (power accelerator actuation) -G186-. (This is an electric motor that is activated by the ECM. This electric motor opens the throttle valve against spring pressure.)
2. Angle sensor -1- for throttle drive (power accelerator actuation) -G187
3. Angle sensor -2- for throttle drive (power accelerator actuation) -G188

Note. The housing for the throttle valve control module must not be opened. The angle sensors are designed as potentiometers (variable resistances). They communicate the position of the throttle valve to the Engine Control Module (ECM) fully independent of each other. The potentiometers cannot be mechanically adjusted. Adjustment is performed in basic setting (function 04) using the VAS5051 tester or the VAG1551 Scan Tool (ST).

Throttle valve control module, adapting

The adaptation teaches the Engine Control Module (ECM) various positions of the throttle valve when the ignition is on and the engine is stopped. These positions are stored in the control module The return communication regarding the position of the throttle valve occurs via the two angle sensors for throttle drive.

An adaptation must always be performed when the throttle valve control module -J338- or the Engine Control Module (ECM) are removed and installed (or replaced) or if voltage supply to the Engine Control Module (ECM) is interrupted.

The learning process (adaptation) occurs

1. Automatically if the ignition is switched on for at least 10 seconds without operating starter and accelerator pedal and the Engine Control Module (ECM) recognizes "adaptation required". (There will be no notification of whether adaptation was successful or not however). Adaptation required is recognized if stored voltage values from the angle sensors do not match actual measured voltage values within a certain tolerance range.
2. Via initiation of basic setting (function 04) display group 060 with ignition on.

Note. Engine will not start during automatic adaptation.

Special tools and equipment

Identifying Special Tools And Equipment. Scheme 513

1. VAS5051 with VAG5051/1 or
2. VAG1551 with VAG1551/3B

Requirements

1. No DTCs in DTC memory, check DTC memory. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) .
2. Engine not running, ignition switched on.
3. Accelerator pedal not depressed.
4. Coolant temperature 10 to 95 °C.
5. Intake air temperature 10 to 90 °C.
6. Supply voltage for ECM larger than 12.7 V. For checking, see «VOLTAGE SUPPLY FOR CONTROL MODULE, CHECKING»(/audi/a6/c5-1997-2001/remont/ignition-system/#ignitionglow-plug-system-28l-v6-atq) .

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Adapting Throttle Valve Control Module (1 Of 4). Scheme 514

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Adapting Throttle Valve Control Module (2 Of 4). Scheme 515

1. Press buttons -0-, -6- and -0- to select "display group number 060" and press -Q- button to confirm input.

After pressing Q -button, throttle valve actuator will be switched on without current.

In this condition, the throttle valve will be drawn into an emergency position by a mechanical spring, which is located in the throttle valve control module. The values supplied by the two angle sensors in this emergency position are stored by the Engine Control Module (ECM).

Next, the throttle valve is opened by a certain value. If this value is reached, the throttle valve actuator is once again de-energized. Now, the mechanical spring must close the throttle valve to the previously learned emergency position within a specified time (spring test).

Then, the throttle valve is closed by the throttle valve actuator; the values supplied by the angle sensors in the throttle valve control unit are stored by the Engine Control Module (ECM).

If Engine Control Module (ECM) should de -energize throttle valve actuator during driving operation, this is expressed by an increased, surging idle speed (RPM). The engine accepts gas only after great delay.

When indicated on display

Identifying Scan Tool Display - Adapting Throttle Valve Control Module (3 Of 4). Scheme 516

1. Check specified values for throttle valve control module in display fields 3 and 4. DISPLAY GROUP 060: ADAPTATION OF THROTTLE VALVE CONTROL MODULE Display fields 1 2 3 4 Display group 060: Adaptation of throttle valve control module Display xx% xx% x - Indicated Throttle valve angle (angle sensor 1) Throttle valve angle (angle sensor 2) Adaptation step counter Adaptation condition Functional range 0 to 100% 0 to 100% 0 to 8 ADP in progress ADP OK ADP ERROR Specified value 3 to 93% 97 to 3% 8 ADP OK Notes After adaptation, the adaptation step counter reaches the number 8 (it is OK for numbers to be skipped) . If "ADP ERROR." is displayed: Check DTC memory . See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) . If specified value is not obtained: See Note below.

Note for display field 3

Different numbers are shown in display field 3 during adaptation that represent the current adaptation condition. It is not particularly important how the adaptation step counter (display field 3) behaves during adaptation, but rather that display field 4 indicates the specification "ADP OK" after adaptation .

Note. The control module can abort adaptation for the following reasons: Throttle valve cannot be closed completely (e.g. contamination) Battery voltage is too low. Throttle valve control module or wire connection is faulty. Engine is started during adaptation or accelerator pedal is operated. Tension of throttle valve housing (check bolts) After termination, tester displays "Function is unknown or cannot be performed at the moment". The next time the ignition is switched on (several seconds), adaptation will be automatically repeated.

Scheme 517

1. End basic adjustment of engine by pressing --> key. (Scheme 521): Identifying Scan Tool Display - Adapting Throttle Valve Control Module (4 Of 4)

Indicated on display (function selection)

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAS5051 with VAG5051/1 or
5. VAG1551 with VAG1551/3B (Scheme 522): Identifying Special Tools And Equipment

Angle sensor 1 for throttle drive (power accelerator actuation) -G187- and Angle sensor 1 for throttle drive (power accelerator actuation) -G188- inform the Engine Control Module (ECM) about the position of the throttle valve. Both angle sensors are located in the throttle valve control module.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Checking Angle Sensor For Throttle Drive (1 Of 3). Scheme 518

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

When indicated on display

Identifying Scan Tool Display - Checking Angle Sensor For Throttle Drive (2 Of 3). Scheme 519

1. Press buttons -0-, -6- and -2- to select "display group number 062" and press -Q- button to confirm input.

Indicated on display

Identifying Scan Tool Display - Checking Angle Sensor For Throttle Drive (3 Of 3). Scheme 520

1. Check specified values for EPC potentiometer voltages in display fields 1 and 2.

DISPLAY GROUP 062: EPC POTENTIOMETER VOLTAGES

Note. Engine Control Module (ECM) calculates the voltage values of the angle sensors in percent relative to 5 volts and displays these percentage values. (5 volts supply voltage represents 100%).

1. Observe display field 1 and 2.
2. Slowly depress accelerator pedal completely. Percent indication in display field 1 must rise uniformly. Tolerance range of 3 to 93% will not be used completely during this. Percent indication in display field 2 must decrease uniformly. Tolerance range of 97 to 3% will not be used completely during this.

Note. The reason why the value indicated in display field 1 climbs, while the value indicated in display field 2 decreases, has to do with the fact that the potentiometers (angle sensors) in the throttle valve control unit run in opposite directions. This means that the voltage tap of angle sensor 1 runs from 0 to 5 volts. (The more the throttle valve is opened, the larger the voltage; percent indication climbs). The voltage tap of angle sensor 2 runs from 5 to 0 volts. (The more the throttle valve is opened, the lower the voltage; the percentage decreases).

If indications do not resemble description

1. Check voltage supply and wire connections of throttle valve control module. See «CHECK VOLTAGE SUPPLY THROTTLE VALVE CONTROL MODULE»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) . Pay particular attention to harness connectors that could be loose or corroded.
2. Check accelerator pedal position sensor. See «THROTTLE POSITION (TP) SENSOR, CHECKING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Scheme 521

1. Pull connector (2) off throttle valve control module.
2. Switch ignition on. (Scheme 526): Identifying Throttle Valve Control Module Harness Connector Terminals
3. Connect multimeter to following connector terminals for voltage measurement: THROTTLE VALVE CONTROL MODULE CIRCUIT TEST: VOLTAGE SUPPLY Harness connector Terminal Specified value 2 + Ground (GND) about 5 V 2 + 6 about 5 V

If specified values are not obtained

Check wire connections from Engine Control Module (ECM) to throttle valve control module. See CHECKING WIRE CONNECTIONS .

Checking wire connections

1. Pull connector (2) off throttle valve control module.
2. Connect VAG1598/31 test box at wiring harness to ECM; do NOT connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
3. Check following wire connections for open circuit and short circuit to Ground (GND) and B+: THROTTLE VALVE CONTROL MODULE CIRCUIT TEST Harness connector Terminal VAG1598/31 test box Socket 1 92 2 83 3 117 4 84 5 118 6 91
4. Repair open circuit or short circuit if necessary.

If no malfunctions are found in wires

1. Replace throttle valve control module.

Scheme 522

1. VAG1526A
2. VAG1594A
3. VAG1598/31
4. VAS5051 with VAG5051/1 or
5. VAG1551 with VAG1551/3B see scheme 151: Identifying Special Tools And Equipment

Both the Throttle Position (TP) sensor -G79- and the Sender -2- for accelerator pedal position -G185- are located at the accelerator pedal and communicate the driver's intentions to the ECM completely independently of each other. Both sensors are stored in one housing.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Checking Throttle Position (TP) Sensor (1 Of 3). Scheme 523

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

When indicated on display

Identifying Scan Tool Display - Checking Throttle Position (TP) Sensor (2 Of 3). Scheme 524

1. Press buttons -0-, -6- and -2- to select "display group number 062" and press -Q- button to confirm input.

Indicated on display

Identifying Scan Tool Display - Checking Throttle Position (TP) Sensor (3 Of 3). Scheme 525

1. Check specified values for EPC potentiometer voltages in display fields 3 and 4.

DISPLAY FIELDS CHART

Note. Engine Control Module (ECM) calculates the voltage values of the angle sensors in percent relative to 5 volts and displays these percentage values. (5 volts supply voltage represents 100%).

1. Observe display field 3 and 4.
2. Slowly depress accelerator pedal completely. Percent indication in display field 3 must rise uniformly. Tolerance range 12 to 97% is not used completely during this. Percent indication in display field 4 must also rise uniformly. Tolerance range of 4 to 49% is not completely utilized.

Note. The indicated value in display field 3 must always be about twice as large as the value in display field 4.

If indications do not resemble description

1. Check voltage supply and wire connections of sensor for accelerator pedal position. See «CHECKING VOLTAGE SUPPLY OF THROTTLE POSITION (TP) SENSOR»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq) .

Scheme 526

1. Remove driver-side storage compartment. See «DRIVER'S STORAGE COMPARTMENT, REMOVING»(/audi/a6/c5-1997-2001/remont/mirrors/#interior-equipment__drivers-storage-compartment-removing).
2. Disconnect harness connector for accelerator pedal position sensor.
3. Switch ignition on. see scheme 155: Identifying Accelerator Pedal Position Sensor Harness Connector Terminals
4. Connect multimeter for voltage measurement as follows: ACCELERATOR PEDAL POSITION SENSOR CIRCUIT TEST: VOLTAGE SUPPLY Harness connector Terminal Specified value 1 + Ground (GND) about 5 V 1 + 5 about 5 V 2 + Ground (GND) about 5 V 2 + 3 about 5 V

If specified values are obtained

1. Also check signal wires.

If specified values are not obtained

1. Check wire connections from Engine Control Module (ECM) to sensors for accelerator pedal position.

Scheme 527

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). (Scheme 533): Identifying Accelerator Pedal Position Sensor Harness Connector Terminals
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: ACCELERATOR PEDAL POSITION SENSOR CIRCUIT TEST Harness connector Terminal VAG1598/31 test box Socket 1 72 2 73 3 36 4 35 5 33 6 34
3. Repair open circuit or short circuit if necessary.

If no malfunctions are found in wires

1. Replace accelerator pedal position sensor. See «ACCELERATOR PEDAL (AP) WITH POSITION SENSORS, REMOVING AND INSTALLING»(/audi/a6/c5-1997-2001/remont/fuel-system/#fuel-supply-system-all-engines) .

Note. For vehicles with automatic transmission, the kick down function must be learned. See KICK DOWN FUNCTION, ADAPTING .

Kick down function, adapting

If the sensor for accelerator pedal position or the Engine Control Module (ECM) is replaced on a vehicle with automatic/variable transmission, the kick down function must be learned by the ECM.

Identifying Special Tools And Equipment. Scheme 528

1. VAS5051 with VAG5051/1 or
2. VAG1551 with VAG1551/3B

1. No DTCs in DTC memory, check DTC memory. See «CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__check-dtc-memory-function-02-and) .
2. Engine not running, ignition switched on.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Adapting Kick Down Function (1 Of 4). Scheme 529

1. Press buttons -0- and -4- to select "Initiate basic setting" and press - Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Adapting Kick Down Function (2 Of 4). Scheme 530

1. Press buttons -0-, -6- and -3- to select "display group number 063" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Adapting Kick Down Function (3 Of 4). Scheme 531

Note. There will be a prompt: "Activate kick-down"

1. Depress accelerator pedal completely, past kick down point, and hold down.

Note. During adaptation of the kick down point, the VAG1551 will display "Kick down ADP in progress". After successful adaptation of the kick down point, the VAG1551 will display "Kick down ADP OK".

1. Check specified value in display field 4.

DISPLAY FIELDS CHART

Note. The abbreviation "ADP" in display field 4 stands for Adaptation. "ERROR" can be indicated, for example, if the accelerator pedal is not immediately pressed in response to a request by the tester or if the accelerator pedal is released while adaptation is running despite the fact that adaptation is not yet complete.In both cases, "Basic Setting" must be exited and the adaptation must be performed again. See KICK DOWN FUNCTION, ADAPTING .

If specified value "ADP OK" is obtained

1. Press right arrow button.

Indicated on display (function selection)

Identifying Scan Tool Display - Adapting Kick Down Function (4 Of 4). Scheme 532

Scheme 533

1. VAG1526A
2. VAG1527B
3. VAG1594A
4. VAG1598/31
5. VAS5051 with VAG5051/1 or
6. VAG1551 with VAG1551/3B see scheme 162: Identifying Special Tools And Equipment

Engine speed signal, checking

Note. The engine speed signal is output at terminal 37 of the Engine Control Module (ECM). The signal is used, among other things, for RPM display in the instrument cluster.

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: ENGINE SPEED SIGNAL CIRCUIT TEST Test box VAG1598/31 Socket Instrument cluster Terminal 37 See SYSTEM WIRING DIAGRAMS
3. Repair open circuit or short circuit if necessary.

Consumption signal for on board computer, checking

Note. The consumption signal is calculated by the ECM from the injection time and directed to the on board computer via terminal 81 of the ECM.

Vehicle speed signal, checking

Note. The vehicle speed signal is generated by the Vehicle Speed Sensor (VSS) -G68- (at transmission) and processed in the instrument cluster. The processed signal enters at terminal 54 of the ECM and is used for idle stabilization and tip-in shock reduction during shifting.

1. Function and display of speedometer OK.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking Vehicle Speed Signal (1 Of 3). Scheme 534

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

When indicated on display

Identifying Scan Tool Display - Checking Vehicle Speed Signal (2 Of 3). Scheme 535

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

Indicated on display

Identifying Scan Tool Display - Checking Vehicle Speed Signal (3 Of 3). Scheme 536

1. Determining via road test whether vehicle speed is displayed in display field 3.
2. If vehicle speed is not display, lift vehicle -if possible using a vehicle hoist- until front left wheel is free.

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Connect VAG1527B voltage tester to sockets 3 (B+) and 54 (VSS) of VAG1598/31 test box.
3. Switch ignition on and turn front left wheel by hand. LED must blink (very brief blink signal).

If LED does not blink

1. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: VEHICLE SPEED SIGNAL CIRCUIT TEST Test box VAG1598/31 Socket Instrument cluster Terminal 54 See SYSTEM WIRING DIAGRAMS
2. Repair open circuit or short circuit if necessary.

Wire for fuel level signal, checking

Note. The Engine Control Module (ECM) receives the fuel level signal from the instrument cluster. The processed signal enters at terminal 30 of the ECM and is used to determine the cause of certain recognized malfunctions (e.g. combustion misfires).

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: WIRE FOR FUEL LEVEL SIGNAL CIRCUIT TEST Test box VAG1598/31 Socket Instrument cluster Terminal 30 See SYSTEM WIRING DIAGRAMS
3. Repair open circuit or short circuit if necessary.

A/C compressor shut -off, checking

Note. The A/C compressor signal communicates to the ECM that the compressor will be switched on in 140 ms. The ECM can switch off the A/C compressor via the same wire connection. Engine Control Module (ECM) switches off A/C compressor: - during hard acceleration (Wide Open Throttle 1st gear) - in emergency mode (emergency operation) - after initiating basic setting (function 04)

1. A/C system OK
2. No DTCs in DTC memory of Engine Control Module (ECM).
3. Vehicle at room temperature (warmer than +15 °C).

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking A/C Compressor Shut -Off (1 Of 3). Scheme 537

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

When indicated on display

Identifying Scan Tool Display - Checking A/C Compressor Shut -Off (2 Of 3). Scheme 538

1. Press buttons -0-, -5- and -0- to select "display group number 050" and press -Q- button to confirm input.

Indicated on display: (1 thru 4 = display fields)

Identifying Scan Tool Display - Checking A/C Compressor Shut -Off (3 Of 3). Scheme 539

1. Switch A/C system off. Specified value in display field 4: Compr. OFF
2. Switch A/C system on using "Auto" button and adjust A/C system to maximum cooling or heating power. Compressor must run. Specified value in display field 4: Compr. ON
3. Depress gas pedal completely (swiftly) and then release it (brief acceleration). Specified value in display field 4: Indication jumps for a few seconds from "Compr. ON" to "Compr. OFF" (compressor is switched off when vehicle accelerates).

If indications do not resemble description

1. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: A/C CONTROL HEAD -E87- CIRCUIT TEST Test box VAG1598/31 Socket A/C control head -E87- Terminal 41 See SYSTEM WIRING DIAGRAMS
3. Repair open circuit or short circuit if necessary.
4. If there are no malfunctions in wiring, check function of A/C system. See «ON BOARD DIAGNOSTIC (OBD)»(/audi/a6/c5-1997-2001/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac) .

A/C system signal, checking

The A/C system signal notifies the Engine Control Module (ECM), that the A/C system requires a higher idle speed to achieve the desired interior temperature (regardless of whether heating or cooling is required).

The increase in idle speed based on presence of the A/C system signal is control module dependent and occurs only in vehicles with All Wheel Drive (AWD) and manual transmission.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Engine must run at idle for this.

When indicated on display

Identifying Scan Tool Display - Checking A/C System Signal (1 Of 2). Scheme 540

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

When indicated on display

Identifying Scan Tool Display - Checking A/C System Signal (2 Of 2). Scheme 541

1. Press buttons -0-, -5- and -6- to select "display group number 056" and press - Q- button to confirm input.
2. Switch on A/C system, press "Auto" button and select lowest temperature.
3. Check indications in display field 3 and 4. DISPLAY FIELDS CHART Display fields 1 2 3 4 Display group 056: Idle stabilization with engine at idle and operating temperature Display xxx/min xxx/min - - Indicated Engine speed (actual) Engine speed (specified) A/C readiness A/C compressor Functional range A/C - LOW A/C - HIGH Compr. OFF Compr. ON Specified value 720 to 820 RPM (1) 670 to 770 RPM (2) 760 RPM (1) 720 RPM (2) A/C - HIGH Compr. ON (1) Front Wheel Drive Vehicles (2) All-Wheel Drive Vehicles

If specified values are not obtained

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: A/C CONTROL HEAD -E87- CIRCUIT TEST: SHORT TO POWER/GROUND Test box VAG1598/31 Socket A/C control head -E87- Terminal 40 See SYSTEM WIRING DIAGRAMS
3. Repair open circuit or short circuit if necessary.
4. If there are no malfunctions in wiring, check function of A/C system. See «ON BOARD DIAGNOSTIC (OBD)»(/audi/a6/c5-1997-2001/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac) .

Brake light switch and brake pedal switch, checking

Note. For safety reasons, the instruction from the accelerator pedal sensor (potentiometer) to the ECM to open the throttle valve is suppressed when brake is being operated. This requires the brake light switch signal and also the brake pedal switch signal in the control module. If brake pedal is operated with accelerator pedal constantly depressed, engine is immediately regulated down to idle speed. A faulty switch can lead to undesired regulation.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Checking Brake Light Switch And Brake Pedal Switch (1 Of 3). Scheme 542

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

When indicated on display

Identifying Scan Tool Display - Checking Brake Light Switch And Brake Pedal Switch (2 Of 3). Scheme 543

1. Press buttons -0-, -6- and -6- to select "display group number 066" and press -Q- button to confirm input.

Indicated on display

Identifying Scan Tool Display - Checking Brake Light Switch And Brake Pedal Switch (3 Of 3). Scheme 544

1. Check brake light/brake pedal switch in display field 2. DISPLAY FIELDS CHART Display fields 1 2 3 4 Display group 066: Signals to Engine Control Module (ECM) Display xxx km/h XXXX xxx km/h XXXX Indicated ACTUAL speed Switch positions SPECIFIED speed Switch positions Functional range XX00 XX11 Specified value XX00 (with brake pedal not operated) XX11 (with brake pedal operated) Notes Value: X = no significance . Switch points slightly offset

If indications do not resemble description

1. Remove driver-side storage compartment. See «DRIVER'S STORAGE COMPARTMENT, REMOVING»(/audi/a6/c5-1997-2001/remont/mirrors/#interior-equipment__drivers-storage-compartment-removing).
2. Disconnect harness connector at brake light switch and brake pedal switch. NOTE: Connector sockets are marked on the back side of the connector. see scheme 174: Identifying Brake Light Switch And Brake Pedal Switch 4-Pin Connector
3. Connect multimeter between terminal 1 and 2 for resistance measurement. Specification: INFINITY ohms (no continuity)
4. Depress accelerator pedal. Specification: approx. 0 ohms
5. Connect multimeter between terminal 3 and 4 for resistance measurement. Specification: approx. 0 ohms
6. Depress accelerator pedal. Specification: INFINITY ohms (no continuity)

If specified values are not obtained

1. Check adjustment of switch or
2. Replace brake light switch / brake pedal switch.

If specified values are obtained

Identifying Brake Light Switch And Brake Pedal Switch Harness Connector Terminals. Scheme 545

1. Connect VAG1527B voltage tester as follows: BRAKE LIGHT SWITCH AND BRAKE PEDAL SWITCH CIRCUIT TEST: TERMINAL 1 Harness connector Terminal Measure to 1 Chassis Ground (GND) LED must light up.
2. Switch ignition on. BRAKE LIGHT SWITCH AND BRAKE PEDAL SWITCH CIRCUIT TEST: TERMINAL 3 Harness connector Terminal Measure to 3 Chassis Ground (GND) LED must light up.

If LED does not light up

1. Check wire connection from terminal 1 or 3 of connector for open circuit and short circuit to Ground (GND)
2. Repair open circuit or short circuit if necessary.

If LED lights up

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
2. Check following wire connections for open circuit and short circuit to Ground (GND) and B+: BRAKE LIGHT SWITCH AND BRAKE PEDAL SWITCH CIRCUIT TEST: TERMINALS 2 & 4 Harness connector Terminal VAG1598/31 test box Socket 2 56 4 55
3. Repair open circuit or short circuit if necessary.

Clutch vacuum vent valve switch -F36-, checking

Note. This signal helps prevent excessive RPM oscillations and tip-in shocks when clutch is disengaged and is required for the cruise control system.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Checking Clutch Vacuum Vent Valve Switch (1 Of 3). Scheme 546

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

When indicated on display

Identifying Scan Tool Display - Checking Clutch Vacuum Vent Valve Switch (2 Of 3). Scheme 547

1. Press buttons -0-, -6- and -6- to select "display group number 066" and press -Q- button to confirm input.

Indicated on display

Identifying Scan Tool Display - Checking Clutch Vacuum Vent Valve Switch (3 Of 3). Scheme 548

1. Check Clutch Pedal Position (CPP) switch in display field 2. DISPLAY FIELDS CHART Display fields 1 2 3 4 Display group 066: Signals to Engine Control Module (ECM) Display xxx km/h XXXX xxx km/h XXXX Indicated ACTUAL speed Switch positions SPECIFIED speed Switch positions Functional range X0XX X1XX Specified value X0XX (at clutch pedal not operated) X1XX (at clutch pedal operated) Notes Value: X = no significance

If indications do not resemble description

Check switch

1. Remove driver-side storage compartment. See «DRIVER'S STORAGE COMPARTMENT, REMOVING»(/audi/a6/c5-1997-2001/remont/mirrors/#interior-equipment__drivers-storage-compartment-removing) .
2. Disconnect harness connector at Clutch Pedal Position (CPP) switch. NOTE: Connector sockets are marked on the back side of the connector.
3. Connect multimeter between terminal 1 and 2 for resistance measurement. Specification: approx. 0 ohms
4. Depress clutch pedal. Specification: INFINITY ohms (no continuity)

If specified value is not obtained

1. Check adjustment of switch or
2. Replace Clutch Pedal Position (CPP) switch.

If specified value is obtained

Checking voltage supply

1. Connect VAG1527B voltage tester as follows: CLUTCH VACUUM VENT VALVE SWITCH CIRCUIT TEST: TERMINAL 1 Harness connector Terminal Measure to 1 Chassis Ground (GND)
2. Switch ignition on. LED must light up.

If LED does not light up

1. Check wire connection from terminal 1 of connector to fuse for open circuit and short circuit to Ground (GND)

If LED lights up

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831). (Scheme 555): Identifying Clutch Vacuum Vent Valve Switch Harness Connector Terminals
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: CLUTCH VACUUM VENT VALVE SWITCH CIRCUIT TEST: TERMINAL 2 Harness connector Terminal VAG1598/31 test box Socket 2 39
3. Repair open circuit or short circuit if necessary.

Wire for crash signal, checking

The Engine Control Module (ECM) receives the crash signal ("Crash shut -off was triggered") from the airbag control module.

When the airbag control module sends the crash signal to the ECM (during an accident or when output DTM is being performed for the airbag system), the ECM switches the Fuel Pump (FP) off. This means that the engine will stop running but can be started again afterward (e.g. to remove vehicle from danger).

1. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831)
2. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: WIRE FOR CRASH SIGNAL CIRCUIT TEST Test box VAG1598/31 Socket Airbag control module -J234- Terminal 67 See SYSTEM WIRING DIAGRAMS
3. Repair open circuit or short circuit if necessary.

If no malfunctions are found in wire

1. Check DTC memory of control module for airbag: See appropriate AIR BAG article in RESTRAINTS.

Rough terrain signal from ABS/EDL control module, checking

Note. When the ABS/EDL control module recognizes that a wheel is spinning, the ABS/EDL control module generates the rough terrain signal. When the Engine Control Module (ECM) recognizes the rough terrain signal, combustion misfire recognition is switched off in the Engine Control Module (ECM). Only check the rough terrain signal if the malfunction "18014 (P1606) rough terrain info/engine torque from ABS cont. mod. Electrical malfunction in circuit" is stored DTC memory.It is possible that the malfunction "Combustion misfire" is also stored in DTC memory as a side effect and it can be disregarded. The wire connection and rough terrain signal are monitored by the Engine Control Module (ECM).

1. Control module coding OK. See «CODE CONTROL MODULE (FUNCTION 07)»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq__code-control-module-function-07) .

1. Switch ignition off.
2. Connect VAG1598/31 test box at wiring harness to ECM; do not connect ECM. See «WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__wire-and-component-test-using-vag159831) .
3. Check following wire connection for open circuit and short circuit to Ground (GND) and B+: ROUGH TERRAIN SIGNAL FROM ABS/EDL CIRCUIT TEST Test box VAG1598/31 Socket ABS control module (w/EDL) -J104- Terminal 74 See SYSTEM WIRING DIAGRAMS

If no malfunctions are found in wire

1. Replace ABS control module.

If the malfunction is indicated again after replacing the ABS control module

1. Replace Engine Control Module (ECM). See «ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING»(/audi/a6/c5-1997-2001/remont/fuel-system/#multiport-fuel-injection-mfi-28l-v6-atq__engine-control-module-ecm-without-metal) .

Data transfer between Engine Control Module (ECM) and CAN capable control modules, checking

Note. Data exchange between individual control modules occurs via a bus system. The term "CAN -bus" refers to a system that transports and distributes data. The wire connections between the control modules, via which data is transferred, are referred to as data wires. Data is transferred to the connected control modules serially (one after the other) via these data wires (i.e. engine speed, accelerator position).

Checking bus system

The DTC table suggested checking the data exchange between the Engine Control Module (ECM) and CAN capable control modules.

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. See «VAS 5051 VEHICLE DIAGNOSTIC, TESTING AND INFORMATION SYSTEM ORVAG1551 SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a6/c5-1997-2001/remont/testing-diagnostics/#on-board-diagnostic-obd-28l-v6-atq) . Ignition must remain switched on for this.

When indicated on display

Identifying Scan Tool Display - Checking Data Transfer Between Engine Control Module (ECM) (1 Of 5). Scheme 549

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

When indicated on display

Identifying Scan Tool Display - Checking Data Transfer Between Engine Control Module (ECM) (2 Of 5). Scheme 550

1. Press buttons -1-, -2- and -5- to select "display group number 125" and press -Q- button to confirm input.
2. Check indications in display fields 1 through 4.

CAN capable control modules connected to the Engine Control Module (ECM) are indicated

1. No indication: Control module not CAN capable
2. Indication 1: CAN capable control module is connected to databus
3. Indication 0: CAN capable control module is not connected to databus

Note. Measuring value blocks 125 and 126 indicate the components that are part of the powertrain data bus.

1. Press right arrow button.

When indicated on display

Identifying Scan Tool Display - Checking Data Transfer Between Engine Control Module (ECM) (3 Of 5). Scheme 551

1. Press buttons -0- and -6- to select "End output" and press -Q- button to confirm input.

When indicated on display

Identifying Scan Tool Display - Checking Data Transfer Between Engine Control Module (ECM) (4 Of 5). Scheme 552

1. Press button 0- twice to select "Automatic test sequence", address word 00. Press -Q- button to confirm input. DTC memory of all OBD capable systems in the vehicle will be checked.

When a control module responds with its identification, the display indicates the number of stored errors or indicates "no malfunctions recognized".

DTCs stored in the system are indicated in sequence and printed out. Then the VAG1551 scan tool sends the next address word.

The automatic test sequence is over when the following indication appears on the display

Identifying Scan Tool Display - Checking Data Transfer Between Engine Control Module (ECM) (5 Of 5). Scheme 553

If a malfunction related to the "powertrain databus" or the "CAN-bus" is indicated

1. Check whether Engine Control Module (ECM) and other CAN capable control modules installed are appropriate for this vehicle (part no. and coding).

If the correct control modules are installed

1. Check to be sure multi -pin connectors of control modules are securely connected.

If multi-pin connectors are properly secured

1. Check CAN bus system

Checking a "two -line bus system"

Three or more control modules are communicating across a "two -line bus system" .

1. Analyze DTCs stored in memories of control modules.

Note. This analysis will help you locate the cause of the line malfunction.

Example 1

From the DTCs stored in the memories, it is determined that control module 1 is not communicating with control modules 2 and 3.

Identifying CAN Bus System (Example 1). Scheme 554

CAN BUS SYSTEM DIAGNOSIS (EXAMPLE 1)

1. Switch ignition off.
2. Disconnect control modules connected across bus wires and check bus wires for an open circuit.
3. Replace control module 1 if no malfunctions can be found in bus wires.

Example 2

From the DTCs stored in the memories, it is determined that control module 2 is not communicating with control modules 1 and 3.

CAN BUS SYSTEM DIAGNOSIS (EXAMPLE 2)

1. Switch ignition off.
2. Disconnect control modules connected across bus wires and check bus wires for an open circuit.
3. Replace control module 2 if no malfunctions can be found in bus wires.

Example 3

Using the DTCs stored in the memories, it is determined that none of the control modules are sending or receiving signals.

CAN BUS SYSTEM DIAGNOSIS (EXAMPLE 2)

Scheme 555

1. Switch ignition off. see scheme 188: Identifying CAN Bus System (Example 3)
2. Disconnect control modules connected across bus wires and check bus wires for a short circuit to B+ and Ground (GND).

If a cause cannot be determined for the DTC "Powertrain databus faulty", check whether the DTC is caused by one of the control modules .

All control modules that use the CAN -bus are still disconnected. Ignition is switched off.

1. Connect one control module.
2. Connect VAG 1551 scan tool. Switch ignition on, and erase DTC memory of control module you just connected. End scan tool output using "End Output" function 06.
3. Switch ignition off and then on.
4. Leave ignition on for 10 seconds. Then, read DTC memory of control module you just connected.
5. If DTC "Powertrain databus faulty" is displayed, replace control module you just connected.
6. If DTC "Powertrain databus faulty" is not displayed, connect next control module and repeat procedure.

See also:
• READINESS CODE, GENERATING
• ENGINE COOLANT TEMPERATURE (ECT) SENSOR -G62-, CHECKING
• BRAKELIGHT SWITCH
• CHECK DTC MEMORY (FUNCTION 02) AND ERASE DTC MEMORY (FUNCTION 05)
• CODING TABLE
• CODE CONTROL MODULE (FUNCTION 07)
• CRUISE CONTROL SYSTEM, ON BOARD DIAGNOSTIC
• FUEL PUMP, CHECKING ELECTRICALLY
• FUEL SUPPLY, FRONT WHEEL DRIVE (FWD)
• FUEL SUPPLY, ALL WHEEL DRIVE (AWD)
• DRIVER'S STORAGE COMPARTMENT, REMOVING
• OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)
• INSTRUMENTS - UP TO 2000
• ON BOARD DIAGNOSTIC (OBD)
• COMPONENT LOCATION FOR SECONDARY AIR INJECTION (AIR) PUMP RELAY -J299
• ENGINE CONTROL MODULE (ECM) (WITH METAL ANTI-THEFT HOUSING), REPLACING
• THROTTLE VALVE CONTROL MODULE, ADAPTING
• KICK DOWN FUNCTION, ADAPTING
• ENGINE CONTROL MODULE (ECM) (WITHOUT METAL ANTI-THEFT HOUSING), REPLACING
• FUEL PRESSURE REGULATOR AND RESIDUAL PRESSURE, CHECKING
• THROTTLE VALVE CONTROL MODULE -J338 -, CHECKING
• WIRE AND COMPONENT TEST USING VAG1598/31 TEST BOX
• TIGHTENING TORQUE
• CHECK WIRE CONNECTIONS FOR MASS AIR FLOW (MAF) SENSOR
• COMPONENT LOCATIONS, OVERVIEW
• CHECKING OXYGEN SENSOR ADAPTATION VALUES AND CONTROL
• CHECKING PRIMARY VOLTAGE
• CHECK OXYGEN SENSOR WIRES BANK 1 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G39
• CHECK OXYGEN SENSOR WIRES BANK 2 FOR HEATED OXYGEN SENSOR (HO2S) 2 -G108
• CHECKING OXYGEN SENSOR CONTROL BEHIND CATALYTIC CONVERTER
• IF SPECIFIED VALUE IN DISPLAY GROUP 037 AND 038 DISPLAY FIELD 3 OR 4 IS NOT OBTAINED
• TESTING OXYGEN SENSOR WIRES
• CHECK OXYGEN SENSOR WIRES FOR OXYGEN SENSOR (O2S) 2 BEHIND THREE WAY CATALYTIC CONVERTER (TWC) -G131-.
• CHECKING WIRE CONNECTIONS