Audi cars are mainly equipped with Bosch control systems, including Bosch Motronic versions 2.3.2, 2.4, 3.2 and 3.8.2, Mono-Jetronic, Mono-Motronic 1.1 and 1.2, KE-Motronic 1.1 and 1.2, KE- 3 Jetronic, Simos, VAG Digifant, VAG MPi and VAG MPFi. All systems control the primary circuit of the ignition system, the injectors and the idling system from one control module. The exception is Mono-Jetronic and KE-3 Jetronic, which control the fuel supply and idling separately.
Engine control systems have a self-diagnosis function that continuously analyses the signals from the engine’s sensors and actuators and compares them with reference values. If the diagnostic program detects a discrepancy, one or more corresponding fault codes are recorded in the memory of the electronic control unit (ECU). Fault codes do not appear if the fault is not under the control of the ACM and if the fault situation is not foreseen by its software.
The control systems installed in Audi vehicles can generate fault codes of two types – 4-digit (“flashing”) and 5-digit. As Audi cars have been improved, the codes and their reading methods have changed. Cars currently in service can be divided into three groups (the dividing point is not always obvious even for the same model).
- Some early release systems can only generate 4-digit codes that can be retrieved using a warning light on the instrument panel (if fitted), an LED or a code reader. Such systems include Mono-Jetronic and Mono-Motronic MA 1.2.1.
- Later systems can generate both 4 and 5 digit codes. 4-digit codes are read using the warning light (if any) or an LED. A reader is required to extract 5-digit codes. These systems include Bosch Motronic versions 2.3, 2.4 and 2.7, KE-3 Jetronic, KE-Matronic and Mono-Motronic (with the old 45-pin BEU connector).
- Even later systems only generate 5-digit fault codes that can only be read with a reader. Such systems include Bosch Motronic versions 2.9, 3.2 and 3.8.2, Mono-Motronic MA1.2.2 (with new 45-pin BEU connector), Simos, VAG Digifant (with 68-pin connector) and VAG MPi and MPFi.
The Audi systems described have a mode of limited controllability (a function known as “limp home” or “crash home”). This means that in the event of certain malfunctions (not all malfunctions trigger this mode), the engine control system is guided not by the sensor readings but by its reference value. This mode allows the car to reach the workshop or service station for inspection and repair, albeit with less efficiency. Once the fault has been rectified, the system returns to normal operation.
Location of diagnostic connector
Mono-Jetronic (Audi 80 and 100 1.8i up to July 1988)
Above the fuel pump relay for “blinking” codes only.
Mono-Jetronic (Audi 80 and 100 1.8i from August 1988)
Two 2-pin connectors in passenger footwell for flashing codes and for the reader.
Bosch Mono-Motronic
Two 2-pin sockets in the passenger footwell for the passenger under the dashboard or in the fuse box on the left in the engine compartment next to the bulkhead. The connectors can be used to extract both the “blink” codes and the reader. The BEU is usually located in the footwell on the driver or passenger side or in the engine compartment behind the bulkhead.
Bosch KE-3 Jetronic and KE-Motronic 1.1 systems
Two 2-pin connectors under the cover above the pedals in the driver’s leg well. The connectors can be used to extract “flashing” codes as well as for the reader.
Bosch KE Motronic 1.2 and Motronic 2.3
Two 2-pin connectors under the cover above the pedals in the driver’s legwell or three 2-pin connectors under the cover above the pedals in the driver’s footwell or in the fuse box in the engine compartment next to the bulkhead. The connectors can be used to extract both the “blinking” codes and the reader.
Bosch Motronic 2.4
Four 2-pin connectors in the passenger footwell niche under the dashboard. The connectors can be used both for extracting “flashing” codes and for the reader.
VAG Digifant
Two 2-pin connectors in the passenger footwell niche under the dashboard or in the fuse box in the engine compartment next to the bulkhead. The connectors can only be used to connect the reader.
VAG MPi and MPFi
Two 2-pin connectors above the pedals in the driver’s leg well, for connection of the reader only.
16-pin connector for on-board diagnostics (A3 models, including Bosch Motronic 3.2, 3.8.2 and Simos)
Located under the cover in the front console.
16-pin connector (other models) – Located under the cover in the rear console next to the ashtray.
Reading errors in Audi cars without special reader
Mono-Jetronic (until July 1988)
- Start the engine and allow it to warm up to operating temperature. The lambda sensor fault codes may only appear after a driving test of at least 10 minutes.
- Stop the engine and switch on the ignition.
- If the engine does not start, turn the starter for at least 6 seconds and leave the ignition on.
- Using a fuse, short the test contacts across the fuel pump relay for at least 5 seconds.
- Remove the fuse and the malfunction light will flash.
- Count the number of flashes in sequence and note the code. To decode its value, refer to the decoding table for the codes.
- Each code is repeated until the fuse is replaced. Insert the fuse and wait 6 seconds before removing it. The next code will flash.
- Continue to extract the codes until code 0000 appears, which means that there are no more codes in the BEU memory.
- If code 4444 appears immediately, it means that no fault codes have been registered.
- At the end of the reading process, switch off the ignition.
Bosch Mono-Jetronic (after July 198V), KBJetronic. KE-Motronic 1.1 and 1.2, Motronic 2.3 and 2.4
- Connect the auxiliary switch to the jacks of the connectors. If the vehicle is not equipped with a fault light on the instrument panel, connect the LED also.
- Start and warm up the engine to operating temperature.
- Stop the engine and turn on the ignition.
If the engine does not start, rotate it with the starter for at least 6 seconds and leave the ignition on. - Close the auxiliary switch for at least 5 seconds. Open the switch and the LED or warning light will start transmitting fault codes, which are to be understood as follows.
- Four numbers are indicated by four series of flashes.
The first series of flashes means the first digit, the second series the second digit, etc. up to the fourth digit.
Each series consists of several flashes lasting 1 or 3 seconds with short pauses in between. Numbers from 1 to 9 are indicated by 1-second flashes, and zero is indicated by a 2-second flash. Each series is separated by a pause of 3.5 seconds. Code 1231 is represented as follows: one 1-second flash, short pause, two 1-second flashes, short pause, three 1-second flashes, short pause, one 1-second flash. The Ambassador’s delay is 3.5 seconds and the code is repeated.
- Count the number of flashes in the series and note the code. To decode the value, refer to the decoding table for the codes.
- Each code is repeated until the fuse is replaced. Insert the fuse and wait 6 seconds before removing it. The next code will flash.
- Continue to extract the codes until code 0000 appears, which means that there are no more codes in the BEU memory.
- If code 4444 appears immediately, it means that no fault codes have been registered.
- At the end of the reading procedure, switch off the ignition and disconnect the LED and switch.
Bosch Mono-Motronic (35-pin version of connector BEU 1.2.1 and 45-pin version 1.2.2)
- Connect the auxiliary switch to the diagnostic sockets. If the vehicle does not have a fault light on the dashboard, also connect the LED between the (+) power supply and pin 33 of the ECU connector (for the 35-pin connector) or pin 3 (for the 45-pin connector). It will be necessary to remove the back of the ECU connector to access the correct pin without disconnecting the connector.
- Start the engine and allow it to warm up to operating temperature. The oxygen sensor fault codes may only appear after a driving test of at least 10 minutes.
- Stop the engine and switch on the ignition.
- If the engine does not start, turn the starter for at least 6 seconds and leave the ignition on.
- Close the auxiliary switch for at least 5 seconds. Open the switch and the LED or warning light will start to transmit fault codes, which are understood as follows.
Four digits are indicated by four series of flashes.
The first series of flashes indicates the first digit, the second series the second digit, etc. up to the fourth digit.
Each series consists of several flashes lasting 1 or 2 seconds with short gaps between them. Numbers from 1 to 9 are indicated by 1-second flashes, and zero is indicated by a 2-second flash.
Each series is separated by a pause of 2.5 seconds.
Code 1231 is presented as follows: one 1-second flash, short pause, two 1-second flashes, short pause, three 1-second flashes, short pause, one 1-second flash. After 2.5 seconds, the code is repeated.
- Count the number of flashes in the sequence and note the code.
- Each code is repeated until you close the auxiliary switch for at least 5.0 seconds and then open it again. The next code will then flash.
- Continue extracting the codes until code 0000 appears, which means that there are no more codes in the BEU memory.
- If code 4444 appears immediately, it means that no fault codes have been registered.
- At the end of the reading process, switch off the ignition and disconnect the LED and switch.
- Systems with a 16-pin onboard diagnostic connector or a 64-pin BEU connector – “Flashing” codes are not provided. The code reader must be used.
Removing the code from memory without the help of the reader
Bosch Mono Jetronic, Mono Motronic, KE Jetronic and KE Motronic
- To remove the codes, follow the procedure described above.
- Switch off the ignition.
- Short-circuit the test contacts with the fuse above the fuel pump relay (Mono-Jetronic only up to July 1988) or the auxiliary switch (other systems).
- Switch on the ignition.
- After 5 seconds, open the switch or remove the fuse. All codes in the memory are deleted.
- Switch off the ignition.
- Switch off the ignition and remove the key. Disconnect the BEU connector for at least 30 seconds.
All systems (alternative method)
- Turn off the ignition and disconnect the negative battery lead for approximately 5 minutes.
- Reconnect the cable to the battery. The first disadvantage of this method is that the BEU will reset all adjusted parameter values to their original state. In order to re-adjust the system to your engine, it is necessary to start the engine from the tire condition and then drive the car at different engine speeds for 20 … 30 minutes. It is also necessary to let the engine idle for about 10 minutes. The second drawback is that you have to reset the radio’s protection code, the current time and other stored values, which are also reset when the battery is disconnected. It is best to use the reader to remove the fault codes.
Audi fault code list (decoding)
| Flashing code | Reader | Fault |
| 4444 | 00000 | No faults |
| 0000 | — | End of code transfer |
| 1211 | 037 | Battery |
| 1212 | 052 | Throttle End Sensor (Idle position) |
| 1111 | 65535 | Internal malfunction BES |
| 1231 | 00281 | Speedometer sensor or chain |
| 1232 | 00282 | Throttle potentiometer |
| 1232 | 00282 | Step Motor Idle Control (Alternate code) |
| 2111 | 00513 | Motor speed sensor or circuit |
| 2112 | 00514 | TDC Sensor or its chain |
| 2112 | 00514 | Crankshaft Angle Sensor |
| 2113 | 00515 | Hall sensor or chain |
| 2114 | 00535 | Ignition Distributor |
| 2121 | 00516 | Stepper Motor Control Idle |
| 2121 | 00516 | Ignition Control valve Chain (Alternate code) |
| 2122 | — | No rotation speed signal Engine |
| 2122 | 00517 | Micro Switchь Extreme situation Throttle (Full load) |
| 2141 | 00535 | Control 1 on detonation (BES) |
| 2142 | 00524 | Detonation sensor 1 or its chain |
| 2142 | 00545 | No signal from automatic transmission |
| 2143 | 00536 | Control 2 on detonation (BES) |
| 2144 | 00540 | Detonation sensor 2 or its chain |
| 2212 | 00518 | Throttle potentiometer or its chain |
| 2214 | 00543 | Engine exceeding Maximum Speed |
| 2222 | 00519 | Absolute pressure sensor In the Collector |
| 2223 | 00528 | Atmospheric pressure sensor or its chain |
| 2224 | 00544 | Exceeding the permissible pressure Turbocharger |
| 2231 | 00533 | Idle control |
| 2232 | 00520 | Air flow sensor with damper or His chain |
| 2232 | 00520 | A mass air flow sensor or Its chain (alternative code) |
| 2233 | 0531 | Air flow sensor with damper or His chain |
| 2233 | 0531 | A mass air flow sensor or Its chain (alternative code) |
| 2234 | 00532 | Improper voltage on-board Network |
| 2242 | 00521 | Potentiometer Adjustment with OR Chain |
| 2312 | 0522 | Temperature sensor Cooling Liquid or its chain |
| 2314 | 00545 | Violation of the electric connection of the engine with the transmission |
| 2322 | 00523 | Air temperature sensor or its chain |
| 2323 | 00522 | Air flow sensor with damper or its chain |
| 2323 | 00522 | Air mass flow sensor or its chain (alternative code) |
| 2324 | 00553 | Air flow sensor with damper or its chain |
| 2224 | 00553 | Air mass flow sensor or its chain (alternative code) |
| 2341 | 00537 | The oxygen sensor control does not work |
| 2342 | 00525 | Oxygen sensor or its chain |
| 2343 | 00558 | Setting up the control of the working mixture, poor |
| 2344 | 00559 | Adjustment of working mix control, rich |
| 2413 | 00561 | The mixture yields beyond the permissible boundaries |
| 4332 | 00750 | Bes |
| 4343 | 01243 | Carbon Filter Control Valve |
| 4411 | 01244 | Nozzle № 1 or its chain |
| 4412 | 01247 | Nozzle № 2 or its chain |
| 4413 | 01249 | Nozzle № 3 or its chain |
| 4414 | 01250 | Nozzle № 4 or its chain |
| 4421 | 01251 | Nozzle № 5 or its chain |
| 4431 | 01253 | Idle control valve or chain |
| 4442 | 01254 | Pressurized pressure control valve or its chain |
| — | 00527 | Inlet collector temperature |
| — | 00530 | Throttle potentiometer or chain |
| — | 00532 | Improper voltage on-board Network |
| — | 00543 | Engine exceeding Maximum Speed |
| — | 00549 | Flow signal |
| — | 00545 | Violation of the electric connection of the engine with the transmission |
| — | 00554 | Control 2 by Oxygen sensor |
| — | 00555 | Oxygen sensor or its chain |
| — | 00560 | Recirculation valve or chain |
| — | 00561 | Mix Management 1 |
| — | 00575 | Absolute pressure sensor in collector |
| — | 00577 | № 1 Cylinder Detonation control |
| — | 00578 | № 2 Cylinder Detonation control |
| — | 00579 | № 3 Cylinder Detonation control |
| — | 00580 | Detonation Control cylinder № 4 |
| — | 00581 | № 5 Cylinder Detonation control |
| — | 00582 | № 6 Cylinder Detonation control |
| — | 00585 | Temperature sensor for exhaust gases Recycling Systems |
| — | 00586 | Recirculation valve or chain |
| — | 00609 | Ignition Amplifier 1 or its chain |
| — | 00610 | Ignition Amplifier 2 or its chain |
| — | 00611 | The ignition amplifier 3 or its chain |
| — | 00624 | Air conditioning |
| — | 00625 | Speedometer sensor |
| — | 00635 | Oxygen sensor heater or sensor circuit |
| — | 00640 | Oxygen sensor or its chain |
| — | 00670 | The potentiometer of the stepper motor of the idling regulator or its chain |
| — | 00689 | Extra Air Inlet Collector |
| — | 00750 | Light Fault Alarm |
| — | 01025 | Light Fault Alarm |
| — | 01087 | Basic installation not completed |
| — | 01088 | Mix composition Control 2 |
| — | 01119 | Transmission number identification signal |
| — | 01120 | Phase Change Control Timing |
| — | 01165 | Throttle potentiometer or chain |
| — | 01182 | Adaptability to height above sea level |
| — | 01235 | Secondary air valve |
| — | 01242 | BES or chain |
| — | 01247 | Carbon filter control valve or chain |
| — | 01252 | № 4 Nozzle valve or valve control circuit |
| — | 01257 | Idle control valve or chain |
| — | 01259 | Relay of fuel pump or relay circuit |
| — | 01262 | Turbocharger pressure Control valve |
| — | 01264 | Secondary air Pump |
| — | 01265 | Recirculation valve or chain |
| — | 16486 | Low mass air flow sensor signal |
| — | 16487 | The signal of the mass air flow sensor above the norm |
| — | 16496 | Weak air temperature sensor signal |
| — | 16497 | Air temperature sensor signal above normal |
| — | 16500 | Coolant temperature sensor or circuit |
| — | 16501 | Low coolant temperature sensor signal |
| — | 16502 | Coolant temperature sensor signal above normal |
| — | 16504 | Throttle potentiometer or chain |
| — | 16505 | Implausible throttle potentiometer Signal |
| — | 16506 | Weak throttle potentiometer Signal |
| — | 16507 | Throttle potentiometer Signal above norm |
| — | 16514 | Oxygen sensor or its chain |
| — | 16515 | Oxygen sensor or its chain |
| — | 16516 | Oxygen sensor signal above normal |
| — | 16518 | Oxygen sensor or its chain |
| — | 16519 | Oxygen sensor and whether its chain |
| — | 16534 | Oxygen sensor or its chain |
| — | 16535 | Oxygen sensor or its chain |
| — | 16536 | Oxygen sensor signal above normal |
| — | 16538 | Oxygen sensor or its chain |
| — | 16554 | Nozzle Group 1 |
| — | 16555 | Nozzle Group 1, poor mix |
| — | 16556 | Nozzle Group 1, Rich mix |
| — | 16557 | Nozzle Group 2 |
| — | 16558 | Nozzle Group 2, poor mix |
| — | 16559 | Nozzle Group 2, Rich mix |
| — | 16684 | Ignition failures |
| — | 16685 | Ignition failures in the cylinder № 1 |
| — | 16686 | Ignition failures in the cylinder № 2 |
| — | 16687 | Ignition failures in the cylinder № 3 |
| — | 16688 | Ignition failures in the cylinder № 4 |
| — | 16689 | Ignition failures in the cylinder № 5 |
| — | 16690 | Ignition failures in the cylinder № 6 |
| — | 16691 | Ignition failures in the cylinder № 7 |
| — | 16692 | Ignition failures in the cylinder № 8 |
| — | 16705 | Engine speed sensor and whether its chain |
| — | 16706 | Motor speed sensor or circuit |
| — | 16711 | Low detonation sensor signal № 1 |
| — | 16716 | Weak detonation sensor signal № 2 |
| — | 16721 | The angle sensor of the crankshaft or its chain |
| — | 16785 | Exhaust Gases |
| — | 16786 | Exhaust Gases |
| — | 16885 | Speedometer sensor or chain |
| — | 16989 | Bes |
| — | 17509 | Oxygen sensor or its chain |
| — | 17514 | Oxygen sensor or its chain |
| — | 17540 | Oxygen sensor or its chain |
| — | 17541 | Oxygen sensor or its chain |
| — | 17609 | № 1 Nozzle needle or control circuit |
| — | 17610 | № 4 Nozzle needle or control circuit |
| — | 17611 | № 3 Nozzle needle or control circuit |
| — | 17612 | № 4 Nozzle needle or control circuit |
| — | 17613 | № 5 Nozzle needle or control circuit |
| — | 17614 | № 6 Nozzle needle or control circuit |
| — | 17615 | № 7 Nozzle needle or control circuit |
| — | 17616 | Needle Nozzle № 8 or control circuit |
| — | 16721 | № 1 Nozzle needle or control circuit |
| — | 16722 | № 2 Nozzle needle or control circuit |
| — | 16723 | № 3 Nozzle needle or control circuit |
| — | 16724 | № 4 Nozzle needle or control circuit |
| — | 16725 | № 5 Nozzle needle or control circuit |
| — | 16726 | № 6 Nozzle needle or control circuit |
| — | 16727 | Ignition failures in the cylinder № 7 |
| — | 16728 | Ignition failures in the cylinder № 8 |
| — | 17733 | Detonation control in the cylinder № 1 |
| — | 17734 | Detonation control in the cylinder № 2 |
| — | 17735 | Detonation control in the cylinder № 3 |
| — | 17736 | Detonation control in the cylinder № 4 |
| — | 17737 | Detonation control in the cylinder № 5 |
| — | 17738 | Detonation control in the cylinder № 6 |
| — | 17739 | Detonation control in the cylinder № 7 |
| — | 17740 | Detonation control in the cylinder № 8 |
| — | 17747 | The signals of speed and rotation angle of the crankshaft were swapped |
| — | 17749 | Channel 1 ignition is short on mass |
| — | 17751 | Channel 2 ignition is short on mass |
| — | 17753 | Channel 3 ignition is short on mass |
| — | 17799 | The turning sensor of the camshaft or its chain |
| — | 17800 | The turning sensor of the camshaft or its chain |
| — | 17801 | Channel 1 ignition |
| — | 17802 | Channel 2 ignition |
| — | 17803 | Channel 3 ignition |
| — | 17808 | Recirculation valve or chain |
| — | 17810 | Recirculation valve or chain |
| — | 17815 | Low recirculation valve control signal |
| — | 17816 | Recirculation valve control signal above norm |
| — | 17817 | Carbon Filter Control Valve |
| — | 17818 | Carbon Filter Control Valve |
| — | 17908 | Relay or fuel pump power supply circuit |
| — | 17910 | Relay or fuel pump power supply circuit |
| — | 17912 | System launches |
| — | 17913 | Micro Throttle position (idling) |
| — | 17914 | Micro Throttle position [Idle] |
| — | 17915 | Idle control valve or chain |
| — | 17916 | Idle control valve or chain |
| — | 17917 | Idle control valve or chain |
| — | 17918 | Idle control valve or chain |
| — | 17919 | Variable inlet manifold control valve or chain |
| — | 17920 | Variable inlet manifold control valve or chain |
| — | 17966 | Throttle Actuator |
| — | 17978 | Immobilizer |
| — | 18008 | Voltage of the on-board network |
| — | 18010 | Battery |
| — | 18020 | Bes |
