Electrical Equipment: Overview Audi TT 8N facelift

General Information

OBD program text/data generated by control modules installed on vehicles from m.y. 2001 may not be recognized by VAG 1551/1552 Scan Tools (ST) with the latest program card. For example: scan tool display shows "text 799", "01529 /references" or similar.

In addition, OBD programs for vehicle electrical equipment updates implemented from m.y. 2001 may also not supported by VAG 1551/1552 Scan Tools (ST) with the latest program card. For example: Powertrain CAN-Bus function - adaptation and addition of Automatic Transmission coding/adaptation etc.).

Only the VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System is capable of processing all display text/data, as well as performing coding, adaptation and related OBD program functions on these vehicles.

OBD program functions on vehicles from m.y. 2001 must be performed using the VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System in mode "Guided Fault Finding".

The instrument cluster contains an electronic speedometer, tachometer, liquid crystal (LCD) displays for odometer, trip odometer, digital clock with date, as well as analog coolant temperature and fuel level gauges. Control and warning lamps are situated within the speedometer and tachometer faces.

A "Driver's Information System " LCD is located between the tachometer and speedometer. Displayed information includes an auto check system, outside air temperature, radio frequency and selectable trip computer functions.

The auto check system integrated with the Driver's Information System monitors the brake system, coolant temperature, fuel level, engine oil pressure, and displays the ambient temperature as a default.

The optional Navigation system display is also included in the Driver's Information System (where applicable).

The instrument cluster is controlled by a microprocessor and has extensive On Board Diagnostic (OBD) capability. If malfunctions occur in any of the system components, corresponding DTCs are stored in the Diagnostic Trouble Code (DTC) memory of the instrument cluster. DTCs are read and identified using VAG 1551 Scan Tool (ST), VAG 1552.Mobile Scan Tool (ST), VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System in mode "Guided Fault Finding".

Note. The descriptions and displays in this section refer only to VAG 1551.

The following adaptation (adjustment) functions are also possible

1. Adapting fuel gauge sender resistance range
2. Adapting fuel consumption display
3. Coding of language versions for on-board computer and Auto Check system
4. Resetting service interval display
5. Setting distance/kilometer counter after replacing instrument cluster

Message "dEF" on trip recorder display

If the control module in the instrument cluster detects a malfunction in its permanent memory, the letters "dEF" will appear on the trip recorder display.

1. If "dEF" appears on the display, replace the instrument cluster. Refer to «Instrument cluster, removing and installing»(ref-276293-S02129256942008010300000).

Notes on replacing instrument cluster

1. The instrument cluster must not be disassembled.
2. If necessary, the instrument cluster can be replaced with an exchange unit (where applicable).
3. Complete the damage report form and return it together with the malfunctioning instrument cluster.
4. Malfunctioning units must always be returned in their original packing.

1. Various input values must be adapted to replacement speedometer. Refer to «Replacement instrument cluster input values, adapting»(ref-276293-S33502622882008010300000).

The instrument cluster contains an electronic speedometer, tachometer, liquid crystal (LCD) displays for odometer, trip odometer, digital clock with date, as well as analog coolant temperature and fuel level gauges. Control and warning lamps are situated within the speedometer and tachometer faces.

A "Driver's Information System" LCD is located between the tachometer and speedometer. Displayed information includes an auto check system, outside air temperature, radio frequency and selectable trip computer functions.

The auto check system integrated with the Driver's Information System monitors the brake system, coolant temperature, fuel level, engine oil pressure, and displays the ambient temperature as a default.

The optional Navigation system display is also included in the Driver's Information System (where applicable).

The instrument cluster is controlled by a microprocessor and has extensive On Board Diagnostic (OBD) capability. If malfunctions occur in any of the system components, corresponding DTCs are stored in the Diagnostic Trouble Code (DTC) memory of the instrument cluster. These can then be identified using VAG 1551 Scan Tool (ST), VAG 1552.Mobile Scan Tool (ST), VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System.

Instrument clusters installed from VIN 8N_Y040001 have expanded Diagnostic Trouble Code (DTC), Read Measuring Value Block and Adaptation information over previous models.

For example: Service Interval Display (SID) adaptation values for USA/CDN models with fixed service intervals

TT models from 09.00 production are equipped with Immobilizer Generation III.

Generation III has the same functionality as the previous version. However, in addition to the normal data exchange between the immobilizer control module and ignition key, Gen. III includes data exchange between the immobilizer control module and Engine Control Module (ECM).

Data exchange between the Immobilizer control module and ECM takes place over the vehicle CAN-Bus network.

Note. For Immobilizer III, the Engine Control Module (ECM) is actively incorporated into the evaluation and monitoring. The control module for immobilizer is integrated into the instrument cluster.

Scheme 1

1. For immobilizer III, the keys are marked with an inscribed "W". The code consists of a fixed code and a variable code portion.

Function

Immobilizer III consists of

1. an adapted control module for anti-theft immobilizer (integrated in instrument cluster)
2. a warning light in instrument cluster
3. an induction coil at ignition lock
4. an adapted Engine Control Module (ECM)

1. and adapted ignition keys with electronics (transponder).

The control module for anti-theft immobilizer is integrated in the instrument cluster, e.g. if control module is malfunctioning, instrument cluster must be replaced. Refer to Instrument cluster, removing and installing.

The anti-theft immobilizer is a system for enabling/locking the Engine Control Module (ECM) via the CAN wire.

The transponder code consists of a fixed code and a variable code. This is different for every start procedure and therefore acts as a copy protection for the transponder.

Every immobilizer contains a different computational rule for the variable code that remains the same for its entire service life. During adaptation of the vehicle key, the immobilizer writes this computational rule into the transponder and simultaneously learns the fixed code of the current key.

The fixed code identifies each individual key so that a key that is lost can be blocked from usage. Each time the ignition is switched on, the induction coil for immobilizer reads the transponder's fixed code and then the variable code and determines whether this key is authorized for vehicle start.

The warning lamp lights up briefly (max. 3 seconds) and then goes out when an authorized vehicle key is used.

When an unauthorized vehicle key is used or when a system malfunction occurs, the warning lamp blinks constantly during ignition "on".

The electronic anti-theft immobilizer is capable of extensive On Board Diagnostic (OBD). If malfunctions occur in any of the system components, corresponding Diagnostic Trouble Codes (DTC) are stored in the DTC memory of the anti-theft immobilizer.

Note. All OBD program functions for anti-theft immobilizer must only be performed using VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System.

Notes for use and adaptation of vehicle key

Engine will only start when an authorized vehicle key is used, i.e. on of the keys adapted to the immobilizer.

During adaptation of the vehicle keys (Refer to Adaptation of vehicle keys ), all vehicle keys, including replacement and emergency keys, must always be adapted to the immobilizer.

If new or extra vehicle keys are required, adaptation of all vehicle keys must be performed.

If adaptation cannot be performed for all vehicle keys, e.g. key lost during a trip, the customer must be informed that adaptation must eventually be performed for any and all vehicle keys.

Especially when a key has been lost, all vehicle keys should be re-adapted, since this will render the lost key unauthorized for vehicle start.

Display group overview

1) Read function where applicable

1) Where applicable

OBD program text/data generated by control modules installed on vehicles from m.y. 2001 may not be recognized by VAG 1551/1552 Scan Tools (ST) with the latest program card. For example: scan tool display shows "text 799", "01529 /references" or similar.

In addition, OBD programs for vehicle electrical equipment updates implemented from m.y. 2001 may also not supported by VAG 1551/1552 Scan Tools (ST) with the latest program card. For example: Powertrain CAN-Bus function - adaptation and addition of Automatic Transmission coding/adaptation etc.).

Only the VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System is capable of processing all display text/data, as well as performing coding, adaptation and related OBD program functions on these vehicles.

OBD program functions on vehicles from m.y. 2001 must be performed using the VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System in mode "Guided Fault Finding".

All cruise control system functions are controlled by the Engine Control Module (ECM). The processing of electronic engine controls and cruise control functions are integrated in the ECM. Other than the cruise control switches on the steering column, the clutch and brake pedal switches and related wiring, there are no separate cruise control components to be serviced.

As all electronic throttle control operations are monitored by On Board Diagnostic (OBD), Diagnostic Trouble Codes (DTC) pertaining to engine electronics that are stored in DTC memory may be relevant to cruise control function.

Always check DTC memory first before troubleshooting CCS (function 02). Refer to

1. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276270-S33964324242008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): AMU
2. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276271-S40733996842008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): ATC
3. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276272-S12227258552008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): AWP
4. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276273-S13756956692008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): BEA

The operating status of the cruise control system, cruise control switches, brake and clutch switches (as inputs to the ECM) can be tested using the following procedure.

Automatic headlight adjustment is required on vehicles with High Intensity Gas Discharge (HID) headlights.

Automatic vertical headlight aim control system keeps the low beams at a constant level even if the car is loaded, a situation which would normally change the headlight angle.

There are two vehicle level sensors, one on the front axle and one on the rear axle. These sensors register the vehicle's fore/aft angle of inclination. The Vehicle Speed Signal (VSS) is also processed.

The control module evaluates these signals and activates the headlight beam adjusting motors when low beams are on.

Function

The automatic vertical headlight aim control system consists of

1. Automatic vertical headlight aim control system control module -J431
2. Left rear level control system sensor -G76
3. Left front level control system sensor -G78
4. Right headlight beam adjusting motor -V48

1. Left headlight beam adjusting motor -V49

When starting the engine, vehicle level is measured and compared to the set point. This signal is sent to the headlight beam adjusting motors which adjust headlight position to this value once, whether or not the low beams are on.

After this single correction, signals to change low beam position will only be sent to the headlight beam adjusting motors with the low beams on.

If a trip is interrupted (vehicle speed less than 1 km/h) and a vehicle position change is recognized due to additional weight (e.g. extra people in the car) the headlights will be automatically adjusted to the proper height.

All changes made by the automatic vertical headlight aim control system are due to static operating conditions.

Note. The following description is only relevant for the VAG1551 scan tool.

The battery is one of the most important electrical components in the modern automobile. A battery that provides trouble-free service has a great influence on customer satisfaction. To ensure trouble-free service and optimum service life, batteries must be checked, serviced and maintained as per the instructions in this article.

Apart from starting the engine, the battery has other tasks. It acts as a buffer and also supplies electrical energy to the complete vehicle electrical system. In addition, the cyclical and capacity demands on the battery have increased due to additional safety and convenience features (electrical consumers) being installed.

The automobile battery has undergone many technical changes and improvements, and development of new battery technologies continues. However, due to physical and chemical limitations, it is not yet possible to consider traditional lead-acid automobile batteries as being totally maintenance free.

Audi TT equipped with the 3.2L V6 engine are equipped with an Absorbed Glass Mat (AGM) battery that requires specific servicing procedures. Refer to Absorbed Glass Mat (AGM) Battery.

All cruise control system functions are controlled by the Engine Control Module (ECM). The processing of electronic engine controls and cruise control functions are integrated in the ECM. Other than the cruise control switches on the steering column, the clutch and brake pedal switches (where applicable) and related wiring, there are no separate cruise control components to be serviced.

As all electronic throttle control operations are monitored by On Board Diagnostic (OBD), Diagnostic Trouble Codes (DTC) pertaining to engine electronics that are stored in DTC memory may be relevant to cruise control function.

Always check DTC memory first before troubleshooting CCS (function 02). Refer to VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System.

The operating status of the cruise control system, cruise control switches, brake and clutch switches (as inputs to the ECM) can be tested using an OBD program. Use VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System in operating mode "Guided Fault Finding".

All cruise control system functions are controlled by the Engine Control Module (ECM). The processing of electronic engine controls and cruise control functions are integrated in the ECM. Other than the cruise control switches on the steering column, the clutch and brake pedal switches (where applicable) and related wiring, there are no separate cruise control components to be serviced.

As all electronic throttle control operations are monitored by On Board Diagnostic (OBD), Diagnostic Trouble Codes (DTC) pertaining to engine electronics that are stored in DTC memory may be relevant to cruise control function.

Always check DTC memory first before troubleshooting CCS (function 02). Refer to

1. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276270-S33964324242008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): AMU
2. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276271-S40733996842008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): ATC
3. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276272-S12227258552008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): AWP
4. «01 ON BOARD DIAGNOSTIC (OBD)»(ref-276273-S13756956692008010300000) for 1.8 LITER 4-CYL. 5V TURBO FUEL INJECTION & IGNITION, ENGINE CODE(S): BEA

The operating status of the cruise control system, cruise control switches, brake and clutch switches (as inputs to the ECM) can be tested using an OBD program procedure. Refer to General information.

The instrument cluster contains an electronic speedometer, tachometer, liquid crystal (LCD) displays for odometer, trip odometer, digital clock with date, as well as analog coolant temperature and fuel level gauges. Control and warning lamps are situated within the speedometer and tachometer faces.

A "Driver's Information System" LCD is located between the tachometer and speedometer. Displayed information includes an auto check system, outside air temperature, radio frequency and selectable trip computer functions.

The auto check system integrated with the Driver's Information System monitors the brake system, coolant temperature, fuel level, engine oil pressure, and displays the ambient temperature as a default.

The optional Navigation system display is also included in the Driver's Information System (where applicable).

The instrument cluster contains an electronic speedometer, tachometer, liquid crystal (LCD) displays for odometer, trip odometer, digital clock with date, as well as analog coolant temperature and fuel level gauges. Control and warning lamps are situated within the speedometer and tachometer faces.

A "Driver's Information System" LCD is located between the tachometer and speedometer. Displayed information includes an auto check system, outside air temperature, radio frequency and selectable trip computer functions.

The auto check system integrated with the Driver's Information System monitors the brake system, coolant temperature, fuel level, engine oil pressure, and displays the ambient temperature as a default.

The optional Navigation system display is also included in the Driver's Information System (where applicable).

The automatic vertical headlight aim control system is installed on vehicles with High Intensity Gas Discharge (HID) headlights.

The system contains the following components

1. Level control system sensors at front and rear axles
2. Headlight range control module
3. Headlight beam adjusting motors integrated with headlight units

When driving, the system automatically adapts the headlight beam inclination dependent on vehicle suspension movement and load. Headlight glare to oncoming traffic is minimized.

Convertible Top Operation Switch -E137-, removing and installing

Removing

1. Remove switch mount in rear center console. Refer to «Switch mount in rear center console, removing and installing»(ref-276293-S35071277212008010300000).

Scheme 2

1. Use small knife or feeler gauge to release retainer tabs -arrows-.
2. Pull switch -2- out of switch mount -1-.

Installing

Install in reverse order of removal of removal, noting the following

1. Press switch into switch mount until fasteners engage.

TT models from 09.00 production are equipped with Immobilizer Generation III.

Generation III has the same functionality as the previous version. However, in addition to the normal data exchange between the immobilizer control module and ignition key, Gen. III includes data exchange between the immobilizer control module and Engine Control Module (ECM).

Data exchange between the Immobilizer control module and ECM takes place over the vehicle CAN-Bus network.

Note. For Immobilizer III, the Engine Control Module (ECM) is actively incorporated into the evaluation and monitoring. The control module for immobilizer is integrated into the instrument cluster.

1. For immobilizer III, the keys are marked with an inscribed "W". The code consists of a fixed code and a variable code portion.

Function

Immobilizer III consists of

1. an adapted control module for anti-theft immobilizer (integrated in instrument cluster)
2. a warning light in instrument cluster
3. an induction coil at ignition lock
4. an adapted Engine Control Module (ECM)

1. and adapted ignition keys with electronics (transponder).

The control module for anti-theft immobilizer is integrated in the instrument cluster, e.g. if control module is malfunctioning, instrument cluster must be replaced. Refer to Instrument cluster, removing and installing.

The anti-theft immobilizer is a system for enabling/locking the Engine Control Module (ECM) via the CAN wire.

The transponder code consists of a fixed code and a variable code. This is different for every start procedure and therefore acts as a copy protection for the transponder.

Every immobilizer contains a different computational rule for the variable code that remains the same for its entire service life. During adaptation of the vehicle key, the immobilizer writes this computational rule into the transponder and simultaneously learns the fixed code of the current key.

The fixed code identifies each individual key so that a key that is lost can be blocked from usage. Each time the ignition is switched on, the induction coil for immobilizer reads the transponder's fixed code and then the variable code and determines whether this key is authorized for vehicle start.

The warning lamp lights up briefly (max. 3 seconds) and then goes out when an authorized vehicle key is used.

When an unauthorized vehicle key is used or when a system malfunction occurs, the warning lamp blinks constantly during ignition "on".

The Audi TT has a single wiring harness (for all connections) instead of separate wiring harnesses.

Always use repair set VAS 1978 when repairing the wiring harness or electrical connectors on the Audi TT

Scheme 3

Wiring harness repair set VAS 1978

Detailed instructions for using VAS 1978 are given in the manual supplied with the repair set.

The manual also gives examples showing how to repair open circuits in wiring and malfunctioning plug connectors.

Note. Repairs must not be performed on shielded wiring associated with the ABS system.

See also:
• 91 RADIO, TELEPHONE, NAVIGATION, TRIP COMPUTER