Decoding Audi engine trouble codes

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