1.8l 4-cyl 5v Turbo Fuel Injection & Ignition, Engine Code(s): Amu Audi TT 8N

On Board Diagnostic (OBD), technical data

Equipment

1. Data is transmitted between the control module and the VAS5051 tester or VAG1551 Scan Tool (ST) via operating mode "Rapid Data Transfer".
2. Diagnostic Trouble Code (DTC) memory is designed for permanent memory and is therefore not dependent on voltage supply.
3. Display of stored DTCs occurs after initiation of display mode. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .
4. DTC memory must be erased after malfunction is repaired. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .

Important!

1. Readiness code must always be regenerated after DTC memory is erased or when voltage supply to the Motronic Engine Control Module (ECM) -J220- is interrupted. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .
2. If the ECM recognizes malfunctions that lead to a degradation of emissions values, it indicates them by lighting the Malfunction Indicator Lamp (MIL) -K83-. Clarification of this lamp. Refer to «Significance of Malfunction Indicator Lamp (MIL)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__significance-of-malfunction-indicator-lamp-mil) .
3. Engine Electronic Power Control (EPC) -relevant malfunctions are indicated by the Electronic Power Control (EPC) warning lamp.

Significance of Malfunction Indicator Lamp (MIL)

If the ECM recognizes malfunctions that lead to a worsening of emissions values, it indicates them by lighting the Malfunction Indicator Lamp (MIL).

Scheme 85

Malfunction Indicator Lamp (MIL)

Note. The Malfunction Indicator Lamp (MIL) can either blink or remain lit continuously. DTC memory should be checked in both cases. Refer to Engine should run at idle . Blinking: There is a malfunction that can cause damage to the catalytic converter (e.g. combustion misfire). In this case, vehicle must only be driven at reduced power! Continuously lit: There is a malfunction that causes increased emissions. Check DTC memory for Motronic ECM and automatic transmission (if equipped). If there are driveability problems or if there is a customer complaint and the MIL is not lit, DTC memory must be checked. There may be DTCs stored that do not cause the MIL to light up immediately, but only if the malfunction is recognized again after repeated engine starts.

Function test

1. Switch on ignition

MIL must light up.

If MIL does not light up when ignition is switched on

1. Check wire from ECM to MIL as follows

If MIL does not light up when ignition is switched on, continue test as follows

1. Start engine and let run at idle

MIL must go out after a few seconds.

If MIL does not go out

1. Check DTC Memory. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .

If there no DTCs are stored

Safety precautions

If special test equipment is required during test drive, observe the following

VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions

Requirements

1. Battery voltage at least 11 V
2. Ground (GND) connections at engine and transmission OK

Work sequence

Scheme 86

1. Connect VAS5051 tester to vehicle with VAS5051/1 diagnostic wire. Alternately, VAG1551 Scan Tool (ST) can be connected using VAG1551/3B adapter.

Note. The following description only explains implementation of On Board Diagnostic using the VAG1551 Scan tool. When using the VAS5051 tester, observe the tester's instructions for use.

Indicated on display

1) Operating modes 1 and 2 are displayed alternately

Note. If nothing appears in display: Refer to Operating instructions of Scan Tool (ST)

Depending on desired function. Refer to Table Selectable functions

1. Switch ignition on.

or

1. Start engine.
2. Press PRINT button to turn on Scan Tool (ST) printer. Indicator lamp in button must light up.
3. Press button 1 to select "Rapid data transfer" operating mode 1.

Indicated on display

Note. The address word 00 initiates the automatic test sequence, i.e. it results in a DTC check on all OBD capable systems in the vehicle via rapid data transfer.

1. Press buttons -0- and -1- to select "engine electronics" and press -Q- button to confirm input.

VAG1551 Scan Tool (ST) display indicates control module identification, e.g.

Note. Control module identification can be printed by pressing the PRINT button of the VAG1551 scan tool.

Control module identification (example)

1. Press --> button.

Indicated on display (function selection)

Note. It will be possible to display the control module identification again after pressing buttons -0- and -1- to select "Check Control Module Versions" and confirming with the -Q- button.

1. If indicated on display

1. Perform troubleshooting procedure after "troubleshooting procedure leak test".

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

Selectable functions

Modes under address word 33

1. Modes 1 to 7 can be selected under address word 33.
2. Individual measured values can be read out via mode 1. Mode 1 is not recommended for authorized Audi dealerships, since this data can be obtained much more accurately via address word 01/function 04 or function 08.
3. Mode 2 displays operating conditions, for which a malfunction was recognized.
4. With mode 3, DTC memory is checked and with mode 4, DTC memory (diagnostic data) is erased.

1. Mode 5 displays the static values of the oxygen sensors, which are legally required. Since these values are not directly relevant to oxygen sensor diagnostics, mode 5 is also insignificant for the authorized Audi dealerships.
2. Under mode 6, all measured values can be checked from components and systems that are not constantly monitored.
3. Using mode 7, DTCs can be checked for which the Malfunction Indicator Lamp (MIL) is not yet lit (MIL is not on, no DTCs under mode 3)

Diagnostic Trouble Code (DTC) memory, checking (scan tool function 02) and erasing (scan tool function 05)

1. Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine should run at idle

Note. If engine does not start, crank engine using starter for at least 5 seconds. Do not switch ignition off afterward under any circumstance.

Indicated on display

1. Press buttons -0- and -2- to select "Check DTC Memory" and press -Q- button to confirm input.

Indicated on display

1. Press --> button.

or

Indicated on display

When printer is switched on, stored DTCs are shown in sequence and printed.

1. Find printed DTCs in DTC table and perform repairs. Refer to «Diagnostic Trouble Code (DTC) table»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__diagnostic-trouble-code-dtc-table) .

Note. If there are no DTCs in the DTC memory, the DTC memory should not be unnecessarily erased or the readiness code will be lost and must then be regenerated. If the DTC memory was erased, generate the readiness code. Refer to Readiness code, generating .

1. Press --> button.

Indicated on display

1. Press buttons -0- and -5- to select "Erase DTC memory" and press -Q- button to confirm input.

Note. Attention! DTC Memory was not interrogated If indicated on display: Procedure was not followed exactly.

1. Check DTC memory.

DTC memory will not be erased under the following conditions

1. Ignition switched off after DTC memory was checked.
2. A static malfunction was not repaired.

Indicated on display

1. Press --> button.
2. Check DTC memory again after repair work is completed

Note. This causes DTCs to be erased that were generated during the repair of the malfunction, e.g. because harness connectors were disconnected.

End Output

Indicated on display

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

Indicated on display

1. Switch off ignition and disconnect diagnostic cable.

Diagnostic Trouble Code (DTC) table

Note. When malfunctions occur in monitored sensors or components, Diagnostic Trouble Codes (DTCs) are stored in the DTC memory with a description of the malfunction type. Electronic Power Control (EPC) -relevant malfunctions are indicated by the EPC warning lamp. Malfunctions that degrade emissions are also indicated by an Malfunction Indicator Lamp (MIL) that is also located in the instrument cluster. There are malfunctions that cause the MIL to light up immediately after recognition. Malfunctions can also occur that do not cause the MIL to light up immediately, but only if those malfunctions are recognized again after repeated engine starts. Malfunctions that occur only sporadically are identified by the letters "SP" (sporadic malfunction) on the VAG1551 scan tool display. The word sporadic means "appearing or occurring at irregular intervals, occasional".

1. The DTC table is organized by the 5 digit code at left.
2. If a stored DTC does not recur within the next 40 warm-up cycles, the DTC will be erased automatically.
3. Do not immediately replace components that the VAG1551 suggests are faulty, instead: Check wire connections and harness connectors to these components according to wiring diagram. Also check Ground (GND) connections according to the wiring diagram. This is particularly valid when malfunctions are displayed as "sporadically occurring" (SP).
4. If the connector is disconnected from the ECM or the battery is disconnected, all adaptation values in the control module are erased. The DTC memory content will however remain intact. If the engine is started after this, a rough, uneven idle can result. In this case, the engine must be allowed to run at idle for a few minutes until the adaptation procedure has been completed.

1. After erasing the DTC memory. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) , generate the readiness code. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .

1) Intake manifold pressure is determined by the charge air pressure sensor -G31- (instead of -G71- as indicated), air pressure is determined by the Barometric Pressure (BARO) sensor -F96- (in ECM).

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

Note on combustion misfires

For malfunctions potentially caused by fuel shortage (e.g. combustion misfires) the DTC "P1250, Fuel Level Too Low" is also indicated. This means that combustion misfires could not be recognized not due to a technical malfunction, but rather because there is/was too little fuel in fuel tank.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) Brake pedal switch -F47- is monitored in addition to Brake light switch -F-.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

Note. mult. = multiplicative, means that malfunction is valid across entire range of engine speed and engine load.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

Note. add = additive, means that malfunction is only valid at closed throttle (idle).

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) The DTC "Fuel Level Too Low" is stored when there is/was too little fuel in fuel tank. The DTC is stored as a static malfunction and is not switched to sporadic even if the fuel tank has been filled with fuel (e.g. by the customer) in the meantime. In this way, it can be determined that subsequent malfunctions were caused by lack of fuel, e.g. combustion misfires or oxygen control related malfunctions.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

2) DTC is stored upon appropriate signal from airbag control module.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

3) For these malfunctions, ECM switches on the MIL in instrument cluster immediately after recognizing the malfunction.

4) For these malfunctions, ECM does not switch on the MIL unless malfunction is recognized again after another engine start.

1) For these malfunctions, ECM switches on the EPC warning lamp in instrument cluster. Significance of EPC warning lamp. Refer to EPC warning lamp -K132- in instrument cluster, significance .

Output Diagnostic Test Mode (DTM) (scan tool function 03)

Note. Output Diagnostic Test Mode (DTM) is only possible with the engine not running and the ignition switched on. The electric fuel pump runs during all of the output Diagnostic Test Mode (DTM). In output Diagnostic Test Mode (DTM) individual actuators are activated for approximately 1 minute unless the next actuator is selected by pressing the --> button. Actuators are checked either acoustically or by touch. Output Diagnostic Test Mode (DTM) is aborted if the engine is started or an RPM signal is recognized. The engine must be started before repeating the output Diagnostic Test Mode (DTM). (ECM must recognize an engine speed of above 300 RPM).

Output Diagnostic Test Mode (DTM) activates the following components in the specified sequence

Requirements

1. Fuses for engine electronics OK
2. Fuel Pump (FP) relay OK

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on.

Indicated on display

1. Press buttons -0- and -3- to select "output Diagnostic Test Mode" and press -Q- button to confirm input.

Indicated on display

Activating EVAP canister purge regulator valve -N80

1. Confirm input using -Q- button.

Indicated on display (Indicated on VAG1551: from EVAP canister purge regulator valve -N80-)

This solenoid valve is activated for 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

If valve is not activated (does not click)

1. Check Evaporative Emission (EVAP) canister purge regulator valve -N80- (tank vent valve). Refer to «Evaporative Emission (EVAP) canister purge regulator valve -N80-, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__evaporative-emission-evap-canister-purge-regulator) .

Activating Secondary Air Injection (AIR) solenoid valve -N112

1. Press --> button.

Indicated on display

This solenoid valve is activated for approximately 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

If valve is not activated (does not click)

1. Check Secondary Air Injection (AIR) solenoid valve -N112-.

Activating Secondary Air Injection (AIR) pump relay -J299

1. Press --> button.

Indicated on display

The Secondary Air Injection (AIR) pump relay -J299- activates the Secondary Air Injection (AIR) pump motor -V101-. This runs for about a minute in intervals, unless --> button is pressed first to switch to the next actuator.

If the Secondary Air Injection (AIR) pump motor does not start up in intervals

1. Check Secondary Air Injection (AIR) pump relay -J299-. Refer to «Secondary Air Injection (AIR) pump relay -J299-, checking and activating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__secondary-air-injection-air-pump-relay) .

Activating Wastegate bypass regulator valve -N75

1. Press --> button.

Indicated on display

This solenoid valve is activated for 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

If valve is not activated (does not click)

Refer to 21 TURBOCHARGER, G-CHARGER

Leak Detection Pump (LDP) -V144- (for tank ventilation system), activating

1. Press --> button.

Indicated on display

The change-over valve in the LDP is activated for approximately 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

Note. The click can be heard by listening in the area of the front right (when looking in driving direction) wheelhousing.

If valve is not activated (does not click)

Refer to 20 - FUEL PUMP, FUEL SUPPLY, EVAPORATIVE EMISSIONS .

Recirculating valve for turbocharger -N249-, activating

1. Press --> button.

Indicated on display

This solenoid valve is activated for 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

If valve is not activated (does not click)

Refer to 21 TURBOCHARGER, G-CHARGER

Check Evaporative Emission (EVAP) canister purge solenoid valve -N115

1. Press --> button.

Note. This solenoid valve is located at the EVAP canister below spare tire well at rear of vehicle under a cover; accessible after raising vehicle.

Indicated on display

This solenoid valve is activated for 1 minute (clicks), unless --> button is pressed first to switch to the next actuator.

If valve is not activated (does not click)

Refer to 20 - FUEL PUMP, FUEL SUPPLY, EVAPORATIVE EMISSIONS

Activating fuel injectors

Note. Fuel injectors are activated in ignition sequence, i.e. cyl. 1, cyl. 3, cyl. 4, cyl. 2.

1. Press --> button.

Indicated on display

1. Press --> button.

Indicated on display

After pressing arrow button, injector must click five times.

If injector does not click

1. Check fuel injectors. Refer to «Fuel injectors, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Press --> button.

Indicated on display

1. Press --> button.

Indicated on display

After pressing arrow button, injector must click five times.

If injector does not click

1. Check fuel injectors. Refer to «Fuel injectors, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Press --> button.

Indicated on display

1. Press --> button.

Indicated on display

After pressing arrow button, injector must click five times.

If injector does not click

1. Check fuel injectors. Refer to «Fuel injectors, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Press --> button.

Indicated on display

1. Press --> button.

Indicated on display

After pressing arrow button, injector must click five times.

If injector does not click

1. Check fuel injectors. Refer to «Fuel injectors, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Press --> button.

Indicated on display

1. Press --> button.

Indicated on display (function selection)

Note. The output Diagnostic Test Mode (DTM) cannot be re-initiated until the engine is started and the ignition switched off and then on again.

Basic Setting (scan tool function 04)

With ignition on and engine not running, the following operations can be performed using "function 04", basic setting

1. Adapt throttle valve control module to Engine Control Module (ECM). Refer to «Throttle valve control module -J338-, adapting»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__throttle-valve-control-module-j338-adapting)

With ignition on and engine running, the following operations can be performed using basic setting

1. Adaptation of oxygen sensor control. Refer to «Checking oxygen sensor adaptation values and control»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-oxygen-sensor-adaptation-values-and)
2. Troubleshooting via targeted activation and deactivation of oxygen sensor control. Refer to «Heated Oxygen Sensor (HO2S) and O2S control before TWC, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__heated-oxygen-sensor-ho2s-and-o2s)

Requirements for operations with engine running

1. No DTCs in DTC memory.
2. Coolant temperature at least 80 ° C.
3. Electrical consumers switched off (radiator coolant fan must NOT run during test).
4. A/C switched off.

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

1. Check DTC Memory. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) . There must not be 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.

Indicated on display

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

Indicated on display

1. Input desired display group number.

Example

1. Press buttons -0-, -0- and -0- to select "display group number 000" and press -Q- button to confirm input.

Note. After selecting display group number, the EVAP canister purge regulator valve is closed and the A/C compressor is switched off.

Indicated on display

Note. For display group number 000, measured values are displayed as a decimal. Display can be printed out on the paper roll when the printer is switched on. To switch to a different display group, proceed as follows

1. Let engine run at idle for a few minutes, coolant temperature at least 80 ° C.
2. If specified values are obtained in all display fields, press --> button.

Indicated on display (function selection)

Control module, coding (scan tool function 07)

If the control module does not indicate coding corresponding to the vehicle, or if the control module has been replaced, code it as follows.

Note. Control module with Part No. 8N0 906 018 T was equipped with "06610" as a permanent code and cannot be re-coded.

1. Connect VAS5051 tester or VAG1551 scan tool and select the control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on for this.

Indicated on display

1. Press buttons -0- and -7- to select "Code control module" and press -Q- button to confirm input.

Indicated on display

1. Input control module coding according to code table. Refer to «Coding table»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__coding-table) .

Clarification of coding

1. Confirm input using -Q- button.

VAG1551 Scan Tool (ST) display indicates control module identification, e.g

Note. Function is unknown or --> cannot be carried out at the moment If indicated on display: Either an unauthorized code number was entered or the control module is not capable of being coded.

1. Press --> button.

Indicated on display (function selection)

Coding table

1) "ESP" stands for Electronic Stability Program

Measuring value block, reading (scan tool function 08)

Requirements

1. Coolant temperature at least 80 ° C.
2. Electrical consumers switched off (radiator coolant fan must NOT run during test).
3. A/C switched off.
4. Steering in "straight-ahead" position

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

Indicated on display

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

Indicated on display

1. Enter desired three digit display group number and confirm by pressing -Q- button.

Note. The display group that should be chosen depends on current function and component tests.

Indicated on display for display group 000

Indicated on display (example) for display group 001

Note. Display can be printed out on the paper roll when the printer is switched on. To switch to a different display group, proceed as follows

Readiness code

The readiness code appears as an 8-digit display in measuring value block 086, display field 1. Each of the 8 digits is allocated to a specific exhaust related system.

If, due to a test which needs to be completed, the function of these systems is checked via output DTM, the position allocated to that system in the 8-digit display is switched from "1" to "0" if the test is completed with "OK".

If a test is completed, but indicated as "not OK", a DTC will be stored in DTC memory. Check DTC Memory. Refer to Engine should run at idle .

When readiness code is generated after a successfully performed test, it reads "00000000".

Readiness code is reset to "11111111" if

1. DTC memory was erased
2. Voltage supply to ECM was cut off (e.g. connector disconnected, battery disconnected)

In this case, readiness code must be re-generated. Refer to Readiness code, generating .

During driving operation in various load conditions, exhaust relevant tests are performed by the control module within a "short trip" and readiness code is generated on its own. In this case, however, concluding control possibilities are not available, meaning that it will not be indicated that all positions of the readiness code are set to "0".

Readiness code, checking

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on.

Indicated on display

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

Indicated on display

1. Press buttons -0-, -8- and -6- to select "display group number 086" and press -Q- button to confirm input.

Indicated on display

1. Check readiness code in display field 1

1. Specification: 00000000

Significance of 8 digit number block for readiness code in display field 1

Note. Readiness code is not generated unless all indicated positions display a 0.

If specified value "00000000" is obtained

1. Press --> button.

Indicated on display (function selection)

If specified value is not obtained

1. Generate readiness code. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .

Readiness code, generating

Special tools and equipment

Scheme 87

1. VAG1788/10 RPM adjuster

Requirements

1. Vehicle stationary
2. Electrical consumers switched off (radiator coolant fan must NOT run during test).
3. Coolant temperature at least 80 ° C

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using address word 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Work step 1: Check DTC Memory

1. Ignition switched on

Indicated on display

1. Press buttons -0- and -2- to select "Check DTC memory" and press -Q- button to confirm input.

Number of stored DTCs or "No DTC recognized" will be indicated on display.

If a DTC is stored

1. Repair malfunction and erase DTC memory. Road test vehicle and then check DTC memory as a control measure.

If no DTCs are stored

1. Press --> button.

Work step 2: Erase DTC Memory

1. Ignition switched on

Indicated on display

1. Press buttons -0- and -5- to select "Erase DTC memory" and press -Q- button to confirm input.

Note. When the DTC memory is erased, the readiness code is reset and must therefore be re-generated.

Indicated on display

1. Press --> button.

Work step 3: Adapt throttle valve control module to Engine Control Module (ECM)

1. Ignition switched on

Indicated on display

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

Indicated on display

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

Indicated on display

1. Check specified values in display fields 3 and 4

If specified value "ADP OK" is obtained

1. Press -C- button.

Work step 4: Diagnostic of tank seal

1. Start engine

Note. After starting the engine, it may be necessary to select the Engine Control Module (ECM) again using address word 01 and the function "Initiate basic setting" using "04".

Requirements

1. Engine running at idle
2. Intake Air Temperature (IAT) less than 95 ° C (display group 4, display field 4)
3. Coolant temperature less than 105 ° C (display group 4, display field 3)

Indicated on display

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

Indicated on display

1. Press buttons -0-, -7- and -1- to select "display group number 071" and press -Q- button to confirm input.

Indicated on display

During test, display field 4 indicates

"Test ON". Maintain test requirements until a diagnostic result is displayed in display field 4.

1. Check specified value in display field 4.

Note. Tank seal test lasts approx. 60 seconds.

Note. If indication in display field 4 jumps from "Test ON" to "Test OFF" during the test and display field 2 indicates "Aborted", repeat "Leak detection diagnostic". When diagnostic is repeated, it can last up to approx. 60 seconds before indication in display field 4 switches from "Test OFF" to "Test ON".

If specified value "System OK" is obtained in display field 4

1. Press -C- button.

Work step 5: Diagnostic of tank ventilation valve

Requirements

1. Engine running at idle
2. Coolant temperature above 80 ° C (display group 4, display field 3)

Indicated on display

1. Press buttons -0-, -7- and -0- to select "display group number 070" and press -Q- button to confirm input.

Indicated on display

1. Check specified value in display field 4.

Note. If test is not initiated or if indication switches from "Test ON" to "Test OFF", depress accelerator pedal briefly, test will be repeated.

1) An indication is only displayed if diagnostic result falls within a specified range due to deviation of idle control and not due to deviation of an oxygen sensor (e.g. sensor 1 from EVAP canister). Otherwise the field remains empty.

If specified value "TVV OK" is obtained

1. Press -C- button.

Work step 6: Diagnostic of fuel supply system

1. Engine running at idle
2. Oxygen sensor control active

Indicated on display

1. Press buttons -1-, -0- and -7- to select "display group number 107" and press -Q- button to confirm input.

Indicated on display

1. Check specified value in display field 4.

If specified value "Syst. OK" is obtained

1. Press --> button.

Work step 7: Checking oxygen sensor heating

1. Engine running at 1800 to 2200 RPM.

Note. Use VAG1788/10 RPM adjuster to achieve increased engine speed.

Indicated on display

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

Indicated on display

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

Indicated on display

1. Check specified values in display fields 1 and 3

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

Important Notes to display fields 1 and 3

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.
2. After reaching operating temperature of the two oxygen sensors, a resistance of less than 2 kOhm must be indicated in display fields 1 and 3.
3. Do not continue test until a resistance of less than 2 kOhm is indicated in display fields 1 and 3.

1. Press --> button.

Work step 8: Diagnostic of operational readiness of oxygen sensors behind catalytic converter

1. Engine running at 1800 to 2200 RPM

Indicated on display

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

Indicated on display

1. Press buttons -0-, -3- and -6- to select "display group number 036" and press -Q- button to confirm input.

Indicated on display

1. Check specified value in display field 2.

If specified value "B1-S2 OK" is obtained

1. Press -C- button.

Work step 9: Secondary Air Injection (AIR) system diagnostic

Note. During diagnostic of the Secondary Air Injection (AIR) system, the Secondary Air Injection (AIR) pump will run for several seconds. Engine running at 1800 to 2200 RPM. Be sure not to leave the RPM range 1800 to 2200 RPM during the duration of the Secondary Air Injection (AIR) diagnostic.

Indicated on display

1. Press buttons -0-, -7- and -7- to select "display group number 077" and press -Q- button to confirm input.

Indicated on display

1. Check specified value in display field 4.

Note. Secondary Air Injection (AIR) system test lasts approx. 60 seconds.

Note. If indication in display field 4 jumps from "Test ON" to "Test OFF" during test (e.g. if RPM goes out of range) and then won't switch back to "Test ON", switch ignition off and on again, repeat "Secondary Air Injection (AIR) diagnostic". Refer to Work step 9: Secondary Air Injection (AIR) system diagnostic . When diagnostic is repeated, it can last up to approx. 60 seconds before indication in display field 4 switches from "Test OFF" to "Test ON".

If specified value "Syst. OK" is obtained

1. Press -C- button.

Work step 10: Diagnostic of oxygen sensor aging before catalytic converter

Requirements

1. In display group 041, display field 1 must indicate a resistance of less than 2 kOhm. Refer to «Work step 8: Diagnostic of operational readiness of oxygen sensors behind catalytic converter»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__work-step-8-diagnostic-of-operational) .
2. Engine running at 1800 to 2200 RPM

Indicated on display

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

Indicated on display

1. Check specified value in display field 4.

If specified value "B1-S1 OK" is obtained

1. Press -C- button.

Work step 11: Diagnostic oxygen sensor control system

1. Engine running at 1800 to 2200 RPM

Indicated on display

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

Indicated on display

1. Check specified value in display field 4.

If specified value "Syst. OK" is obtained

1. Press -C- button.

Work step 12: Diagnostic of oxygen sensor aging behind catalytic converter

1. Engine running at 1800 to 2200 RPM.

Indicated on display

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

Indicated on display

1. Check specified value in display field 4.

If specified value "B1-S2 OK" is obtained

1. Press -C- button.

Work step 13: Diagnostic of catalytic converter

1. Engine continues to run at 1800 to 2200 RPM.

Indicated on display

1. Press buttons -0-, -4- and -6- to select "display group number 046" and press -Q- button to confirm input.

Indicated on display

1. Check specified value in display field 4.

Note. Catalytic converter diagnostic lasts approx. 60 seconds.

If specified value "Cat B1 OK" is obtained

1. Press --> button.

Work step 14: Readiness code, reading

1. Read readiness code. Refer to «Readiness code, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-checking) .

If special testing equipment is required during test drive, observe the following

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.)

1. When the system is open: Do not work with compressed air if it can be avoided. Do not move vehicle unless absolutely necessary.
2. Disconnected electrical harness connectors: Protect from dirt and moisture. Be sure harness connector is dry before connecting.

Technical data

Scheme 88

Components A and B are not depicted in the overview illustration.

A - Leak Detection Pump (LDP) -V144- (behind right front wheelhousing liner)

B - Evaporative Emission (EVAP) canister purge solenoid valve (at EVAP canister, under spare tire well, accessible from below)

1 - 4-pin harness connector

1. For Heated Oxygen Sensor (HO2S) -G39- and Oxygen Sensor (O2S) heater -Z19
2. Location: On right at bulkhead
3. Heated Oxygen Sensor (HO2S) -G39- (bank 1, sensor 1) is threaded directly into the exhaust manifold
4. Location of Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- with O2S heater 1 behind TWC -Z29-. See «Installed position of Oxygen Sensor (O2S) behind Three Way Catalytic Converter (TWC) -G130- with O2S heater 1 behind TWC -Z29- and cover for oxygen sensor harness connector»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

2 - Motronic Engine Control Module (ECM) -J220

3 - Ignition coils -N-, -N128-, -N158-, -N163

4 - Recirculating valve for turbocharger -N249

1. Location. See «Installed position: Recirculating valve for turbocharger -N249»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

5 - Combination valve for secondary air injection (AIR)

1. Checking, removing and installing

Refer to 26 EXHAUST SYSTEM, EMISSION CONTROLS

6 - Throttle Position (TP) sensor -G79- and Sender -2- for accelerator pedal position -G185

1. Location. See «Installed position: Throttle Position (TP) sensor -G79- and Sender -2- for accelerator pedal position -G185»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

7 - Brake light switch -F- and Brake pedal switch -F47

1. Location. See «Location: Brake light switch -F- and Brake pedal switch -F47»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

8 - Clutch vacuum vent valve switch -F36

1. Location. See «Location: Clutch vacuum vent valve switch -F36»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

9 - Electronic Power Control (EPC) warning lamp -K132

1. Location. See «Location: EPC warning lamp -K132»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

10 - Secondary Air Injection (AIR) pump relay -J299- and main relay (Motronic ECM power supply relay -J271-)

1. Below cover, on left at bulkhead
2. Location. See «Installed position: Secondary Air Injection (AIR) pump relay -J299- and Motronic ECM power supply relay -J271»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

11 - Mass Air Flow (MAF) sensor -G70

1. Checking. Refer to «Secondary Air Injection (AIR) pump relay -J299-, checking and activating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__secondary-air-injection-air-pump-relay)

12 - Wastegate bypass regulator valve -N75

13 - Engine Coolant Temperature (ECT) sensor -G62

14 - Fuel pressure regulator

15 - Knock Sensor (KS) 2 -G66

16 - Charge air pressure sensor -G31

17 - Engine Speed (RPM) sensor -G28

18 - Throttle valve control module -J338

1. 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 Air Temperature (IAT) sensor -G42

20 - 3-pin harness connector

1. 3x
2. Location. See «Location: 3-pin harness connectors»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)
3. For Knock Sensor (KS) 1 -G61
4. For Engine speed (RPM) sensor -G28

1. For Knock Sensor (KS) 2 -G66

21 - Secondary Air Injection (AIR) solenoid valve -N112

22 - Fuel injectors -N30- through -N33

23 - Knock Sensor (KS) 1 -G61

24 - Secondary Air Injection (AIR) pump motor -V101

1. Checking

Refer to 26 EXHAUST SYSTEM, EMISSION CONTROLS

25 - Pressure switch/power steering -F88

1. Location. See «Installed position: Pressure switch/power steering -F88»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)

26 - Camshaft Position (CMP) sensor 2 -G163

27 - Evaporative Emission (EVAP) canister purge regulator valve -N80

Scheme 89

1. Location: On cylinder head cover

1 - To connection at intake manifold

2 - Vacuum reservoir

3 - To mechanical recirculating valve

4 - Recirculating valve for turbocharger -N249

5 - To Secondary Air Injection (AIR) solenoid valve -N112

Scheme 90

Scheme 91

Scheme 92

Scheme 93

Note. Slightly further up, there is a second clutch pedal switch that must be operated so that the starter will crank the engine. It is not involved directly with the engine injection and ignition system.

Scheme 94

1 - For Knock Sensor (KS) 1 -G61

2 - For Engine speed (RPM) sensor -G28

3 - For Knock Sensor (KS) 2 -G66

Scheme 95

Scheme 96

1 - Oxygen sensor behind catalytic converter (B1-S2)

2 - Cover; harness connector for oxygen sensor is located under this cover

Scheme 97

1 - Secondary Air Injection (AIR) pump relay -J299

2 - Main relay (Motronic Engine Control Module (ECM) power supply relay -J271-)

Scheme 98

1 - Seal

2 - Mass Air Flow (MAF) sensor -G70

3 - Phillips-head screw

4 - Air duct

5 - 5-pin harness connector

6 - Phillips-head screw

7 - Air cleaner housing, upper portion

8 - Air cleaner element

9 - Nut, 10 Nm

10 - Air intake connection

11 - Air cleaner housing, lower portion

12 - Hex bolt, 10 Nm

Electrical testing 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. Procedure. Refer to 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 if 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.).

Special tools and equipment

Scheme 99

1. VAG1598/31 Test box

Work sequence

1. Switch ignition off.
2. Remove windshield wiper arms (unscrew).
3. Disconnect cover for plenum chamber and place it on windshield side.
4. Disengage locking lugs and remove control module connector.

Scheme 100

1. Connect VAG1598/31 test box to connector of wiring harness. Ground (GND) clip (arrow) at test box must be clipped to battery Ground. Relevant test procedures note if Engine Control Module (ECM) should also be connected to test box.
2. Perform test as described in relevant repair sequence.

Note. Important notes after re-connecting Engine Control Module (ECM)

1. Check DTC memory and erase it if necessary. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .
2. Generate readiness code. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .

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.

Procedure after interruption of voltage supply

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.

Special tools and equipment

Scheme 101

1. VAS5051 with VAG5051/1

or

1. VAG1551 with VAG1551/3B

Work sequence

Perform the following steps after an interruption in the voltage supply

1. Check DTC memory and erase it if necessary. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .
2. Generate readiness code. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .

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

Removing ECMs with metal anti-theft housing. Refer to Engine Control Module (ECM) - with metal anti-theft housing, replacing .

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

Special tools and equipment

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Removing

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on.

VAG1551 Scan Tool (ST) display indicates control module identification, e.g.

1. First, always allow display of control module identification and print it out. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .
2. Compare coding with coding versions. Refer to «Coding table»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__coding-table) .
3. Switch ignition off.
4. Remove windshield wiper arms (unscrew).

1. Disconnect cover for plenum chamber and place it on windshield side.
2. Disengage locking lugs and remove control module connector.

Scheme 102

1. Use a screwdriver to press locking lugs of bracket to side and then remove Engine Control Module (ECM) toward front.

Installing

Installation is reverse of removal, noting the following

1. Bend back locking lug of bracket.

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.

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

1. Check DTC memory and erase it if necessary. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .
2. Observe notes for coding new Engine Control Module (ECM). Refer to «Control module, coding (scan tool function 07)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
3. For vehicles with cruise control (discernable at steering column), switch this free in ECM

Refer to 01 ON BOARD DIAGNOSTIC (OBD)

1. Adapt immobilizer to Engine Control Module (ECM) (only if installed)

Refer to 01 ON BOARD DIAGNOSTIC (OBD)

1. For vehicles with automatic (or continuously variable) transmission, kick down position of pedal value sensor must be learned. Refer to «Kick down function, adapting»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__kick-down-function-adapting) .

1. Generate readiness code. Refer to «Readiness code, generating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__readiness-code-generating) .

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

Removing ECMs without metal anti-theft housing. Refer to Engine Control Module (ECM) - without metal anti-theft housing, replacing .

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

Removing

1. Connect VAS5051 tester and select vehicle system "01 - Engine Electronics". Ignition must be switched on.

Scheme 103

VAS5051 tester display will indicate the control module identification and coding -2-.

1. Always allow display of control module identification first and print it out.
2. Switch ignition off.
3. Pry off both caps at wiper arms using a screwdriver.

Scheme 104

1. Loosen hex nuts (arrows) several turns.
2. Loosen wiper arms -1- from wiper axle by lightly tilting.
3. Remove hex nuts completely and remove wiper arms.
4. Remove plenum chamber cover rubber seal -2-.

1. Remove plenum chamber cover -3- and place it on windshield side.

Note. Item -1- in (Scheme 105) shows the Engine Control Module (ECM) with anti-theft housing.

Scheme 105

1. Use a screwdriver to press locking lug of bracket (arrow) to side and then remove Engine Control Module (ECM) toward front.

Scheme 106

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

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

To disconnect the harness connectors from the Engine Control Module (ECM) (e.g. 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

Equipment required

Scheme 107

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

Work sequence

1. "Flip" Engine Control Module (ECM) with anti-theft housing in direction of engine compartment so that locking mechanism (item -2- in see scheme 27 ) becomes visible and place a clean rag below Engine Control Module (ECM) with anti-theft housing.

Scheme 108

1. 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.

Note. Next, use the heat gun to heat the threads of the locking mechanism into which the snap-off screws are screwed. This step loosens the locking compound on the threads of the snap-off screws for easier removal.

Scheme 109

1. 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.
2. Switch on heat gun and heat up thread for approx. 20 to 25 seconds.

Scheme 110

1. Next, using locking pliers -1-, grab screw head -2- and remove snap-off screw by turning in direction of arrow.

The procedure for the second snap-off screw is exactly the same. Be very careful since the control module connector is in close proximity.

Scheme 111

1. 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.
2. Switch on heat gun and heat up threads for approx. 20 to 25 seconds.

Scheme 112

1. Next, using locking pliers -1-, grab screw head -2- and remove snap-off screw by turning in direction of arrow.

The Engine Control Module (ECM) can now be removed from the metal anti-theft housing.

1. Disengage connectors from Engine Control Module (ECM) and then disconnect connectors.
2. Remove old Engine Control Module (ECM) and insert new one.

Installing

Installation is the reverse order of removal, noting the following

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

1. Bend back locking lug of bracket.

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

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

Use VAS5051 tester.

Idle speed, checking

Special tools and equipment

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Requirements

1. Exhaust system free of leaks.
2. Coolant temperature at least 80 ° C.
3. Electrical consumers switched off (radiator coolant fan must NOT run during test).
4. A/C switched off.

1. No pressure gauges (e.g. for fuel pressure test) connected.

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 -N80- is closed and the A/C compressor is switched off

Work sequence

1. Check DTC Memory. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) . There must not be 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.

Indicated on display

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

Indicated on display

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

Indicated on display

1. Check whether engine speed in display field 1 (actual engine speed) is within tolerated range.

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 --> button.

Indicated on display (function selection)

If specified value is not obtained

1. Check DTC memory again. Refer to «Engine should run at idle»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-should-run-at-idle) .

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. Check false air in intake air system. Refer to «Intake system, checking for leaks (unmetered air)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__intake-system-checking-for-leaks-unmetered) .
2. Check throttle valve control module. Refer to «Throttle valve control module -J338-, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__throttle-valve-control-module-j338-checking) .
3. Check if Evaporative Emission (EVAP) canister purge regulator valve always open. Refer to «Evaporative Emission (EVAP) canister purge regulator valve -N80-, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__evaporative-emission-evap-canister-purge-regulator) .
4. Perform adaptation of throttle valve control module. Refer to «Throttle valve control module -J338-, adapting»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__throttle-valve-control-module-j338-adapting) .

Significance of 5 digit indication of display group 056

System pressure, fuel pressure regulator and residual pressure, checking

Special tools and equipment

Scheme 113

1. VAG1318 Pressure gauge
2. VAG1318/7 Adapter

Scheme 114

1. VAG1318/17 (2x) Adapter

Note. The fuel pressure regulator regulates fuel pressure according to the 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.

Requirements

1. Fuel Pump (FP) relay OK, checking. Refer to «Fuel Pump (FP) relay -J17-, checking and activating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Fuel Pump (FP) OK, checking

Refer to 20 - FUEL PUMP, FUEL SUPPLY, EVAPORATIVE EMISSIONS

1. Fuel filter OK
2. Battery voltage at least 11 V

Checking system pressure

1. Open fuel filler flap briefly (pressure release).

Scheme 115

1. Remove fuel supply hose -1- (with white marking) from supply line, press release button for this.

Scheme 116

1. Connect VAG1318 using adapters 1318/7 and 1318/17 (2 pieces) at supply line.
2. Open shut-off valve of pressure gauge. Lever points in direction of flow.
3. Start engine and let run at idle.
4. Measure fuel pressure.

1. Specification: about 2.5 bar positive pressure

Scheme 117

1. Disconnect vacuum hose at fuel pressure regulator (arrow).

1. Fuel pressure must rise to about 3.0 bar positive pressure.

1. Switch ignition off.
2. Check for proper seal and residual pressure by observing pressure drop on pressure gauge.

1. After 10 minutes, there must be at least 1.5 bar positive pressure

If residual pressure sinks below 1.5 bar positive pressure

1. Start engine and let run at idle.

Scheme 118

1. Wait until pressure has built up, and then switch off ignition. Immediately close shut-off valve of VAG1318 pressure gauge (lever perpendicular to direction of flow -arrow-).
2. Observe pressure drop on pressure gauge.

If pressure does not drop now

1. Test check-valve on transfer Fuel Pump (FP).

If pressure drops again

1. Open shut-off valve of VAG1318 pressure gauge (lever in direction of flow -arrow-).
2. Start engine and let run at idle.
3. Wait until pressure has built up, and then switch off ignition. Then immediately clamp return line (with blue marking) completely closed.

If pressure does not drop now

1. Replace fuel pressure regulator

If pressure drops again

1. Check wiring connections, O-rings at fuel rail and fuel injectors for proper seal.
2. Check whether pressure gauge is properly sealed.

Note. Before disconnecting the pressure gauge, release the pressure by opening the shut-off valve. Hold a container in front of the connection for this.

Scheme 119

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1527B Voltage tester
3. VAG1594A Connector test kit
4. VAG1598/31 Test box

Checking internal resistance

1. Disconnect harness connector at fuel injector to be tested.

Note. In order to prevent a mix-up of the harness connectors at the fuel injectors, each group of two connectors are connected with a plastic track.

Scheme 120

1. Check resistance of individual fuel injectors.

1. Specification: 12 to 13 ohms (at room temperature)

If specified value is not obtained

1. Replace fuel injector. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

If specified value is obtained

Checking voltage supply

Requirements

1. Fuel Pump (FP) relay OK, checking. Refer to «Fuel Pump (FP) relay -J17-, checking and activating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .
2. Fuse for fuel injectors OK

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Disconnect harness connector at the fuel injector to be tested.

Note. In order to prevent a mix-up of the harness connectors at the fuel injectors, each group of two connectors are connected with a plastic track.

Scheme 121

1. Connect VAG1527B voltage tester as follows

1. Operate starter briefly (engine can also start).

1. LED must light up

If LED does not light up

1. Check wiring connection between terminal 1 and fuse for fuel injector for open circuit.

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Repair open circuit if necessary.

If LED lights up

1. Check activation of fuel injectors

Checking activation of fuel injectors

Requirement

1. Internal resistance of valve OK

1. Slide back rubber boot of fuel injector connector, but leave connector connected.

Scheme 122

1. Connect VAG1527B voltage tester between sockets 2 (signal) and 1 (B+).
2. Operate starter briefly (engine can also start).

1. 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

1. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connections for open circuit and short circuit to Ground (GND) and B+

1. Repair open circuit or short circuit if necessary.

If wiring connection is OK

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

Scheme 123

1 - Fuel injector insert, 3 Nm

1. Apply locking compound D 000 600 A2 to insert.

2 - O-ring

1. Removing and installing. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)
2. Always replace
3. Coat with clean engine oil

3 - Fuel injectors -N30- through -N33

1. Removing and installing. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)
2. Always replace
3. Coat with clean engine oil

4 - Supply hose

5 - Return hose

6 - Harness connector

1. For injectors
2. 4x

7 - Socket-head screw, 10 Nm

8 - Fuel pressure regulator

9 - O-ring

1. Always replace

10 - O-ring

1. Always replace

11 - Retaining clip

12 - Fuel rail

13 - O-ring

1. Removing and installing. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu)
2. Always replace
3. Coat with clean engine oil

14 - Retaining clip

1. Make sure clip is correctly seated on fuel injector and fuel rail

15 - 10 Nm

16 - Throttle valve control module -J338

1. 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

17 - Gasket

1. Always replace

18 - 10 Nm

19 - Intake Air Temperature (IAT) sensor -G42

20 - O-ring

1. Always replace

21 - Intake manifold

Scheme 124

1. Remove engine cover (arrows).
2. Disconnect wiring/connectors at

1. Fuel injectors -N30-, -N31-, -N32-, -N33
2. Intake Air Temperature (IAT) sensor -G42
3. Camshaft Position (CMP) sensor 2 -G163
4. Throttle valve control module -J338

1. Detach cable channel to fuel injectors.

1. Disconnect fuel supply line -1- and fuel return line -2- by pressing on release buttons at separating point.

1. Disconnect vacuum hose from fuel pressure regulator.
2. Unscrew 2 socket-head bolts (Refer to «Fuel rail with fuel injectors, disassembling and assembling»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) , item no. 7 ) for fuel rail.
3. Remove fuel rail with injectors from intake manifold simultaneously upward and set aside in rear of engine compartment on a clean cloth.
4. Disengage retaining clip and remove fuel injector.

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

Installation is reverse of removal, noting the following

1. Remove O-rings at all opened connections. (Never remove plastic cap from head of fuel injector. To replace front O-ring, pry O-ring off over plastic cap).
2. Always coat O-rings with clean engine oil.
3. Make sure fuel injectors are in place and seated correctly
4. Check clip for unobstructed fitting.

1. Place fuel rail with secured fuel injectors onto intake manifold, and apply uniform pressure to press it in.

Tightening torque

Scheme 125

Special tools and equipment

1. VAG1348/3-2 Adapter cable
2. VAG1348/3A Remote control
3. VAG1594A Connector test kit
4. VAG1602 Injection quantity test device

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

1. or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Requirement

1. Fuel pressure OK, checking. Refer to «System pressure, fuel pressure regulator and residual pressure, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__system-pressure-fuel-pressure-regulator-and) .

Work sequence

1. Remove fuel rail including fuel injectors from intake manifold. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) . Fuel lines remain connected.
2. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .
3. Bridge terminals 1 and 65 at test box using adapter cables from VAG1594A connector test kit (this step supplies ground to one side of relay coil for fuel pump relay).

Checking proper seal

1. Switch ignition on.

Note. After switching ignition on, the fuel pump will run continuously even with the engine not running. This is because: the fuel pump relay is supplied with B+ via the central electronics after the ignition is switched on. The fuel pump relay receives negative via the cable bridge in the test box.

1. Check proper seal of fuel injectors (visual inspection). With fuel pump running, only 1-2 drops per minute may drip out per injector.
2. If fuel loss is greater, stop fuel pump from running (switch off ignition) and replace faulty fuel injector. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Checking injection quantity

1. Insert fuel injector to be tested in a measuring glass from VAG1602 injection quantity test device.

Scheme 126

1. Connect one terminal of fuel injector to engine ground using an adapter cable and an alligator clip from VAG1594A connector test kit.
2. Connect second terminal of fuel injector to B+ using VAG1348/3A remote control, VAG1348/3-2 adapter cable and assisting cable.
3. Switch ignition on.

1. Fuel Pump (FP) must run.

1. Activate VAG1348/3A remote control for 30 seconds.
2. Perform measurement on all fuel injectors.
3. After all four fuel injectors have been activated, place measuring glasses on an even surface.

1. Specified value for each fuel injector: 179 ± 14 ml

1. If measured value of one or more fuel injectors is outside of specified range, switch fuel pump off (switch ignition off) and replace faulty fuel injector. Refer to «Removing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Note. Also check spray pattern when checking injection quantity. Spray pattern must be the same for all injectors

1. Re-install fuel injectors together with fuel rail. Refer to «Installing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Scheme 127

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1594A Connector test kit
3. VAG1598/31 Test box

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

The engine must be turning for the Fuel Pump (FP) relay -J17- to close, i.e. the relay does not receive Ground (GND) (via the Engine Control Module -ECM-) until the ECM recognizes RPM signals.

Note. The Fuel Pump (FP) relay is located at position 4 of the micro-central electronics in the driver's footwell, left.

Requirement

1. Battery voltage at least 11 V

Function test of Fuel Pump (FP) relay

1. Remove driver-side storage compartment.

Refer to 68 - INTERIOR EQUIPMENT

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on.

1. Initiate output Diagnostic Test Mode. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) and activate Evaporative Emission (EVAP) canister purge regulator valve -N80- (Tank Ventilation Valve).

Scheme 128

1. Fuel Pump (FP) relay (at position 4 of micro-central electronics in driver footwell, left) must trigger and Fuel Pump (FP) must run.

If relay does not trigger

1. Check activation of Fuel Pump (FP) relay.

If Fuel Pump (FP) does not run

1. Check voltage supply for Fuel Pump (FP) and components (via fuel pump relay). Refer to «Check voltage supply for Fuel Pump (FP) and components»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Checking activation of Fuel Pump (FP) relay

1. Switch ignition off.
2. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .
3. Connect socket 65 and socket 2 of test box to each other using adapter cable from VAG1594 connector test kit.
4. Switch ignition on.

1. Fuel Pump (FP) relay (at position 4 of micro-central electronics in driver footwell, left) must trigger.

If relay triggers now, but did not during output DTM

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

If relay does not trigger

1. Switch ignition off.
2. Remove Fuel Pump (FP) relay.

Scheme 129

1. Connect multimeter to terminal 19 of relay socket and Ground (GND) for voltage measurement.
2. Switch ignition on.

1. Specification: approx. battery voltage

If specified value is not obtained

1. Check wiring connections

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

If specified value is obtained

1. Switch ignition off.

1. Check following wiring connection for open circuit and short circuit to Ground (GND) and B+

1. 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).

Scheme 130

1. Disconnect fuses S228, S232, S234 and S243 (positions 28, 32, 34 and 43) from fuse holder.
2. Initiate output Diagnostic Test Mode (DTM). Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) 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.

If specified values are not obtained

1. Repeat test at another terminal of fuse socket.

If specified values are not obtained again

1. Check wiring connections

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

If no malfunctions are detected

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

Scheme 131

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1594A Connector test kit
3. VAG1598/31 Test box
4. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

1. or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Requirements

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

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

Checking function

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

Indicated on display

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 -N80- is closed and the A/C compressor is switched off

Indicated on display

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

Indicated on display

1. Check specified values for load detection.

If specified value is obtained

1. Press --> button.

Indicated on display (function selection)

Evaluation display group 002

Evaluation display group 002

Voltage supply for Mass Air Flow (MAF) sensor, checking

1. Disconnect connector from Mass Air Flow (MAF) sensor.

Scheme 132

1. Connect multimeter for voltage measurement as follows.

1. Operate starter briefly.

1. Specification: approx. battery voltage

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

If specified value is not obtained

1. Check wiring connection from terminal 2 of connector to Fuel Pump (FP) relay via fuse for open circuit and short circuit to Ground (GND)

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Repair open circuit or short circuit if necessary.

1. Connect multimeter to terminal 2 and terminal 3 of connector for voltage measurement.
2. Operate starter briefly.

1. Specification: approx. battery voltage

Note. Ground (GND) from the ECM is present at terminal 3 of connector.

If specified value is not obtained

1. Check wiring connections. Refer to «Check wiring connections for Mass Air Flow (MAF) sensor»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__check-wiring-connections-for-mass-air) .

1. Connect multimeter to terminal 3 and terminal 4 of connector for voltage measurement.
2. Switch ignition on.

1. Specification: about 5 V

If specified value is not obtained

1. Check wiring connections. Refer to «Check wiring connections for Mass Air Flow (MAF) sensor»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__check-wiring-connections-for-mass-air) .

Check wiring connections for Mass Air Flow (MAF) sensor

Note. Signal wire is also checked during wiring test.

1. Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connections for open circuit and short circuit to Ground (GND) and B+

1. Repair open circuit or short circuit if necessary.
2. Also check all wires for short circuit to each other.

If wiring connection is OK

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

Intake system, checking for leaks (unmetered air)

Special tools and equipment

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

or

1. VAG1551 Scan Tool with VAG1551/3B Adapter
2. Engine leak detection spray G 001 800 A1

Note. 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. It is absolutely necessary to follow the safety precautions listed on the leak detection spray can.

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle for this.

Indicated on display

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

Indicated on display

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

Indicated on display (1 to 4 = display fields)

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 --> button.

Indicated on display (function selection)

If engine speed decreases

1. Press --> 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 problem.

Function of O2S control before Three Way Catalytic Converter (TWC)

Note. The oxygen sensor compares oxygen content of air with residual oxygen content in the exhaust and delivers a voltage signal to the control module. The voltage signal "mixture rich (too little residual oxygen)" is 0.7 to 1.1 V (relative to reference Ground). The voltage signal "mixture lean (too much residual oxygen)" is -0.1 to +0.3 V (relative to reference Ground). At the transition from "rich" to "lean" and vice versa ( lambda = 1.0) voltage will jump from between 0.7 and 10.1 V to between -0.1 and +0.3.3 V (or vice versa). Due to the steep voltage jump, oxygen sensor control cannot maintain the ideal mixture of lambda = 1.0 as constant. Oxygen sensor control constantly fluctuates back and forth between the conditions "slightly too lean" and "slightly too rich".

Note. If voltage change does not occur or occurs only slowly, the following malfunctions could be present: Slits or holes in sensor head clogged. Sensors suffered thermal overload. Transition resistance in signal wire or Ground (GND) wire. Sensor too cold, sensor heating not functioning. 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). 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).

Heated Oxygen Sensor (HO2S) and O2S control before TWC, checking

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1594A Connector test kit
3. VAG1598/31 Test box
4. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

1. or

1. VAG1551Scan Tool with VAG1551/3B Adapter

Note. For the specified troubleshooting procedure, it is possible to switch oxygen sensor control off by selecting display group 99 under "Basic Setting" and switch it on again under "Read Measuring Value Block". After selecting display group 99 (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. For location of the oxygen sensors and harness connectors. Refer to Overview of component locations .

Requirements

1. Road test performed and DTC memory erased.
2. Coolant temperature at least 80 ° C.

Function test

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

Indicated on display

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

Note. During Basic Setting, the EVAP canister purge regulator valve -N80- is closed and the A/C compressor is switched off

Indicated on display

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

Indicated on display

1. Check oxygen sensor status in display field 1.

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

Significance of 3 digit indication of display group 030

Note. The first field of the 3 digit indication (heating) fluctuates between 0 and 1.

Checking oxygen sensor adaptation values and control

1. Press -C- button.
2. Press buttons -0-, -3- and -2- to select "display group number 032" and press -Q- button to confirm input.

Indicated on display

1. Check oxygen sensor control in display fields 1 and 2.

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

Indicated on display

1. Check oxygen sensor control in display fields 1 and 2.

Continued

If specified value in display field 1 is not obtained or if value does not fluctuate at least 2 %

1. Road test vehicle in order to free oxygen sensor of possible residue and repeat test.

If specified value in display field 1 is not obtained even after road test or if value does not fluctuate at least 2 %

1. Check primary voltage. Refer to «Checking primary voltage»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-primary-voltage) .
2. Check oxygen sensor heating. Refer to «Oxygen Sensor (O2S) heating for HO2S before and after TWC, checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__oxygen-sensor-o2s-heating-for-ho2s) .
3. Check oxygen sensor before catalytic converter for aging. Refer to «Oxygen Sensor (O2S) aging (HO2S before TWC), checking»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__oxygen-sensor-o2s-aging-ho2s-before) .

Evaluation display group 032

Evaluation display group 032

Evaluation display group 033

Checking primary voltage

1. Disconnect 4-pin harness connector (black) to oxygen sensor before catalytic converter; installed position. Refer to «Overview of component locations»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Scheme 133

1. Connect multimeter between terminal 3 and 4 for voltage measurement.
2. Switch ignition on.

1. Specification: 0.400 to 0.500 V

1. Switch ignition off.

If specified value is not obtained

1. Check oxygen sensor wiring. Refer to «Checking oxygen sensor wiring»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-oxygen-sensor-wiring)

If specified value is obtained

1. Replace Heated Oxygen Sensor (HO2S) -G39-.

Checking oxygen sensor wiring

1. Disconnect 4-pin harness connector (black) to oxygen sensor before catalytic converter.
2. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connections for open circuit.

1. Repair open circuit if necessary.
2. Check wires to each other for short circuit.

If wiring connection is OK

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

Oxygen Sensor (O2S) aging (HO2S before TWC), checking

Special tools and equipment

1. VAG1788/10 RPM adjuster

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Requirement

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

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

Indicated on display

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

Indicated on display

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

Indicated on display

1. Use VAG1788/10 RPM adjuster to adjust engine speed to between 1800 and 2200 RPM.
2. Continue test as soon as display 4 indicates "Test ON".

Note. This process can take a few minutes.

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.

If specified value in display field 3 and 4 is not obtained

1. Road test vehicle in order to free oxygen sensor of possible residue and repeat test.

If specified value in display field 3 and 4 is not obtained, even after road test

1. Replace Heated Oxygen Sensor (HO2S) -G39-.

Heated Oxygen Sensor (HO2S) and O2S control after TWC, checking

Note. Oxygen sensor control behind catalytic converter overrules oxygen sensor control before catalytic converter and is responsible for control correction. 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 this time is in the negative range (i.e. 50 ms), mixture is shifted in the -lean- direction.

The 4-pin harness connector for the oxygen sensor behind catalytic converter and oxygen sensor heating is under cover -2- at vehicle floor.

Scheme 134

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1594A Connector test kit
3. VAG1598/31 Test box
4. VAG1788/10 RPM adjuster

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

1. or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Requirements

1. Road test performed and DTC memory erased.
2. Coolant temperature at least 80 ° C.

Work sequence

1. Connect VAS5051 tester or VAG1551 scan tool and select control module for engine electronics using "address word" 01. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Engine must run at idle.

Indicated on display

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

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

Indicated on display

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

Indicated on display

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 350 ° C.

Note. This process can take a few minutes.

1. Press -C- button.
2. Use VAG1788/10 RPM adjuster to adjust engine speed to between 1800 and 2200 RPM.

Indicated on display

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

Indicated on display

1. Check oxygen sensor status for oxygen sensor behind catalytic converter in display field 2.

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

Significance of 3 digit indication of display group 030

Note. Oxygen sensor control of oxygen sensor behind catalytic converter (B1-S2) is not active without engine load. The first position of the 3 digit indication (heating) fluctuates between 0 and 1.

Checking oxygen sensor control behind catalytic converter

1. Press -C- button.

Indicated on display

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

Indicated on display

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

Note for display field 3

Oxygen sensor control behind catalytic converter overrules oxygen sensor control before catalytic converter and is responsible for control management. 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 display group 037

If specified value in display field 3 and 4 is not obtained

1. Road test vehicle in order to free oxygen sensor of possible residue and repeat test.

If specified value in display field 3 and 4 is not obtained, even after road test

1. Replace Heated Oxygen Sensor (HO2S) -G39-.

Note. If oxygen sensor voltage is OK and dwell time of oxygen sensor control behind catalytic converter is still above 1200 ms, even after a road test, this suggests aging of the oxygen sensor before catalytic converter.

1. Disconnect the 4-pin harness connector to the oxygen sensor behind catalytic converter (below a black plastic cover at underside of vehicle)

1. Connect multimeter between terminal 3 and 4 for voltage measurement.
2. Switch ignition on.

1. Specification: 0.400 to 0.500 V

1. Switch ignition off.

If specified value is not obtained

1. Check oxygen sensor wiring. Refer to «Checking oxygen sensor wiring»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

If specified value is obtained

1. Replace oxygen sensor behind catalytic converter.

1. Disconnect 4-pin harness connector to oxygen sensor behind catalytic converter (below a black plastic cover at underside of vehicle).
2. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connections for open circuit.

1. Repair open circuit if necessary.
2. Check wires to each other for short circuit.

If wiring connection is OK

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

Oxygen Sensor (O2S) heating for HO2S before and after TWC, checking

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1594A Connector test kit
3. VAG1598/31 Test box

Requirements

1. Coolant temperature at least 80 ° C
2. Fuse for oxygen sensor heating OK

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

Work sequence

1. Disconnect 4-pin harness connector to oxygen sensor before catalytic converter; Component location overview. Refer to «Overview of component locations»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) . or
2. Disconnect 4-pin harness connector to oxygen sensor behind catalytic converter; Component location overview. Refer to «Overview of component locations»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Scheme 135

1. Connect multimeter between terminal 1 and 2 of relevant connector for resistance measurement.

1. Specified value at room temperature: 1 to 5 ohms

Note. At higher temperatures, resistance climbs sharply.

If specified value is not obtained

1. Replace Oxygen Sensor (O2S).

If specified value is obtained

1. Check voltage supply of oxygen sensor heating. Refer to «Checking voltage supply for oxygen sensor heating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-voltage-supply-for-oxygen-sensor) .

Checking voltage supply for oxygen sensor heating

1. Connect multimeter between terminal 1 (B+, from Fuel Pump) and 2 (Ground, from ECM) for voltage measurement.
2. Start engine.

1. 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 switched on and off at these points. It is therefore possible that the voltage displayed on the tester will fluctuate. When the ECM switches oxygen sensor heating on and off it can be observed, if necessary, in the function "Read Measuring Value Block" display group number 041.

If there is no voltage

1. Connect multimeter for voltage measurement as follows

1. Operate starter briefly.

1. Specification: approx. battery voltage

If there is no voltage again

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

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

If voltage supply is OK

1. Connect multimeter for voltage measurement as follows

1. Start engine.

1. Specification: approx. battery voltage, possibly fluctuating

1. Switch ignition off.

If there is no voltage

1. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connection for open circuit

Oxygen sensor heater for oxygen sensor before catalytic converter

Oxygen sensor heater for oxygen sensor behind catalytic converter

1. Repair open circuit if necessary.

If wiring connection is OK, but there is no Ground (GND) supply for oxygen sensor heating

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

Heated Oxygen Sensor (HO2S), removing and installing

Special tools and equipment

Scheme 136

1. 3337/9 socket wrench insert SW16
2. Locking compound G 052 112 A3

Work sequence

1. Disconnect 4-pin harness connector of relevant oxygen sensor and lay it to side.

Note. For location of the oxygen sensors and harness connectors. Refer to Overview of component locations .

1. Unscrew appropriate oxygen sensor using special tool 3337/9.

Note the following when installing

Note. Oxygen sensor wiring must always be secured in the same position when installing so that contact with the exhaust pipe is avoided. Oxygen sensor threads are coated with an assembly paste. This paste must not contact sensor openings. Tightening torque: 55 Nm

Scheme 137

The Secondary Air Injection (AIR) system causes the catalytic converter to heat up more quickly, resulting in earlier operational readiness following a cold start.

Principle

Due to over-enrichment of the mixture during the cold start phase, there is an increased amount of un-burned carbon monoxide in the exhaust. Secondary Air Injection (AIR) improves secondary oxidation in the catalytic converter and therefore reduces emissions. The heat produced by secondary oxidation greatly reduces start-up time for the catalytic converter, therefore improving exhaust quality during the cold start phase significantly.

Function

1. In the cold start phase, the ECM -2- activates the secondary air pump -12- via the relay for secondary air pump -1-. Air reaches the combination valve for Secondary Air Injection (AIR) -10-.
2. The Secondary Air Injection (AIR) valve -3- is activated in parallel, which allows the vacuum to reach the combination valve for Secondary Air Injection (AIR) -10- and the vacuum diaphragm for boost pressure regulation -7-. The combination valve for Secondary Air Injection (AIR) thereby opens the path for secondary air to the exhaust channels of the cylinder head.

1. To prevent unnecessary torque losses, secondary air is routed to the turbine wheel of the turbocharger -8- so that air can get directly into the catalytic converter. For this, the boost pressure regulation pressure unit opens the boost pressure valve -7-. The pressure unit, designed as a double reservoir, has a vacuum connection for this on the intake side.

1 - Secondary Air Injection (AIR) pump relay -J299

2 - Motronic Engine Control Module (ECM) -J220

3 - Secondary Air Injection (AIR) solenoid valve -N112

4 - Intake manifold

5 - Check-valve

1. Installed position (light/dark side): Arrow points in direction of flow, as shown

6 - Vacuum reservoir

7 - Pressure unit for boost pressure regulation

8 - Turbocharger

9 - Cylinder head

10 - Combination valve for secondary air injection (AIR)

11 - Air filter housing

12 - Secondary Air Injection (AIR) pump motor -V101

Scheme 138

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1527B Voltage tester
3. VAG1594A Connector test kit
4. VAG1598/31 Test box

1. VAS5051 Vehicle diagnosis, testing and information system

1. or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Component location. Refer to Overview of component locations , Overview of component locations

Requirement

1. Output Diagnostic Test Mode (DTM) performed

Checking internal resistance

1. Disconnect harness connector from Secondary Air Injection (AIR) valve -N112-.

Scheme 139

1. Connect multimeter at valve for resistance measurement.

1. Specification: 25 to 35 ohms

1. If specified value is not obtained, replace Secondary Air Injection (AIR) solenoid valve -N112-.

Checking voltage supply

1. Disconnect harness connector from Secondary Air Injection (AIR) valve -N112-.

Scheme 140

1. Connect VAG1527B voltage tester as follows

1. Operate starter briefly (engine can also start).

1. LED must light up

If LED does not light up

1. Perform following tests marked with dots

1. Check fuse S243 (in fuse holder, position 43).

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Check wiring connection from terminal 1 of connector via fuse S243 (in fuse holder, socket 43) to Fuel Pump (FP) relay for open circuit

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Check Fuel Pump (FP) relay. Refer to «Fuel Pump (FP) relay -J17-, checking and activating»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Checking activation

1. Connect VAG1527B voltage tester as follows

1. Initiate output Diagnostic Test Mode (DTM) and activate Secondary Air Injection (AIR) solenoid valve -N112-. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Indicated on display

1. LED must blink.

If LED does not blink or if it remains constantly lit

1. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .

1. Check following wiring connections for open circuit and short circuit to Ground (GND) and B+

1. Repair open circuit or short circuit if necessary.

If wiring connection is OK

1. Replace Engine Control Module (ECM). Refer to «Engine Control Module (ECM) - without metal anti-theft housing, replacing»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__engine-control-module-ecm-without) .

Secondary Air Injection (AIR) pump relay -J299-, checking and activating

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1527B Voltage tester
3. VAG1594A Connector test kit
4. VAG1598/31 Test box

Component location. Refer to Overview of component locations

1. Initiate output Diagnostic Test Mode (DTM) and activate Secondary Air Injection (AIR) pump relay -J299-. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

1. Secondary Air Injection (AIR) pump relay -1- (under cover, left, at bulkhead) must trigger and the Secondary Air Injection (AIR) pump motor -V101- must run in intervals. The relay -2- need not be observed in this context (it is involved supplying voltage for the Motronic ECM power supply relay -J271-.

A - If relay does not trigger

1. Check voltage supply of Secondary Air Injection (AIR) pump relay. Refer to «Checking voltage supply of Secondary Air Injection (AIR) pump relay»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-voltage-supply-of-secondary-air) .
2. Check activation of the Secondary Air Injection (AIR) pump relay. Refer to «Checking activation of Secondary Air Injection (AIR) pump relay»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-activation-of-secondary-air-injection) .

B - If relay triggers, but Secondary Air Injection (AIR) pump does not run

1. Check voltage supply of the Secondary Air Injection (AIR) pump motor. Refer to «Checking voltage supply of Secondary Air Injection (AIR) pump motor»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Checking voltage supply of Secondary Air Injection (AIR) pump relay

1. Switch ignition off.

1. Remove Secondary Air Injection (AIR) pump relay -1-.

Scheme 141

1. Connect multimeter for voltage measurement as follows (left relay carrier)

Note. Socket allocation of the relay carrier is printed on the relay carrier itself. Specification: approx. battery voltage

If specified value is not obtained

1. Perform following tests marked with dots

Scheme 142

1. Check fuse S131 (50 A) in main fuse box/battery.
2. Check wiring connection from B+ (terminal 30) to fuse S131 for Secondary Air Injection (AIR) pump relay -J299- (below cover, left, at bulkhead) for open circuit.

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

1. Connect multimeter for voltage measurement as follows (left relay carrier)

1. Operate starter briefly (engine can also start).

1. Specification: approx. battery voltage

If specified value is not obtained

1. Perform following tests marked with dots

1. Check fuse S243 (in fuse holder, position 43).
2. Check wiring connection from B+ (terminal 30) to fuse S131 for Secondary Air Injection (AIR) pump relay -J299- (below cover, left, at bulkhead) for open circuit.

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

Checking activation of Secondary Air Injection (AIR) pump relay

1. Switch ignition off.
2. Remove Secondary Air Injection (AIR) pump relay

1. Connect multimeter for voltage measurement as follows (left relay carrier)

1. Initiate output Diagnostic Test Mode (DTM) and activate Secondary Air Injection (AIR) pump relay -J299-. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

1. Specification: Approx. battery voltage, fluctuates because relay from ECM is not constantly switched on during output Diagnostic Test Mode (DTM) but is alternately switched on and off instead.

If specified value is not obtained

1. Switch ignition off.
2. Connect VAG1598/31 test box at wiring harness to ECM but do not connect ECM: Refer to «Electrical testing using VAG1598/31 test box»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__electrical-testing-using-vag159831-test-box) .
3. Check following wiring connection for open circuit and short circuit to Ground (GND) and B+

1. Repair open circuit or short circuit if necessary.

If no malfunctions are detected

1. Replace Secondary Air Injection (AIR) pump relay -J299-.

Scheme 143

1. Remove center sound insulation (arrows).

Scheme 144

1. Disconnect connector for Secondary Air Injection (AIR) pump motor -1- -V101-.
2. Connect VAG1527B voltage tester between terminals 1 and 2
3. Initiate output Diagnostic Test Mode (DTM) and activate Secondary Air Injection (AIR) pump relay -J299-. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

1. LED must blink

If LED does not blink

1. Perform following tests marked with dots

1. Check wiring connection from connector at Secondary Air Injection (AIR) pump motor -V101- to Secondary Air Injection (AIR) pump relay -J299- (in relay carrier below cover, left, at bulkhead) for open circuit

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

Important!

1. Check wiring connection from connector at Secondary Air Injection (AIR) pump motor -V101- to Ground (GND) point in engine compartment, left, for open circuit

Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations

If no malfunctions are detected

1. Replace Secondary Air Injection (AIR) pump motor -V101-.

Evaporative Emission (EVAP) canister purge regulator valve -N80-, checking

Special tools and equipment

1. VAG1526A or Fluke 83 Multimeter
2. VAG1527B Voltage tester
3. VAG1594A Connector test kit
4. VAG1598/31 Test box

1. VAS5051 Vehicle diagnosis, testing and information system with VAG5051/1 Adapter

or

1. VAG1551 Scan Tool with VAG1551/3B Adapter

Note. The Evaporative Emission (EVAP) canister purge regulator valve -N80- is also called the "Tank Ventilation Valve (TVV)" or "EVAP valve".

Checking for proper seal

When there is no current, the Evaporative Emission (EVAP) canister purge regulator valve -N80- is closed.

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. Refer to «VAS5051 vehicle diagnostic, testing and information system orVAG1551 Scan Tool (ST), connecting and selecting functions»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__vas5051-vehicle-diagnostic-testing-and-information) .

Ignition must remain switched on.

1. Initiate output DTM and activate EVAP canister purge regulator valve -N80-. Refer to «Output Diagnostic Test Mode (DTM) (scan tool function 03)»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu) .

Indicated on display

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 EVAP canister purge regulator valve -N80-.

Checking internal resistance

1. Disconnect connector at EVAP valve.

Scheme 145

1. Connect multimeter at valve for resistance measurement.

1. Specification: 22 to 30 ohms

If specified value is not obtained

1. Replace EVAP canister purge regulator valve -N80-.

If specified value is obtained

1. Check voltage supply. Refer to «Checking voltage supply»(/audi/tt/8n-1998-2003/remont/fuel-system/#18l-4-cyl-5v-turbo-fuel-injection-ignition-engine-codes-amu__checking-voltage-supply) .

Checking voltage supply

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

Requirement

1. Fuse for EVAP valve OK.

1. Disconnect connector at EVAP valve.

Scheme 146

1. Connect VAG1527B voltage tester as follows