Home » General guide – Diagnostic trouble codes for AudiA3 Sportback

General guide – Diagnostic trouble codes for AudiA3 Sportback

Diagnostic trouble code (DTC) format
EOBD codes
DTC terminology

Diagnostic trouble code (DTC) format

Prior to 2000 there was no uniformity in the display, format or method of retrieval of diagnostic trouble codes, each vehicle manufacturer developing a dedicated system with special diagnostic equipment and varying amounts of data logging. Some systems having just a few one or two digit codes while others had more comprehensive three and four digit coding systems.
In many cases the codes for these early systems could be displayed by connecting an LED tester or jump wire between the appropriate terminals of the data link connector (DLC) and counting the LED or malfunction indicator lamp (MIL) flashes or groups of flashes.
For example Fig. 1 is displaying trouble code 3. The MIL is displaying three short flashes, with a short pause separating each flash. If more than one code has been logged, a long pause would be used to separate each code.
If the trouble code is greater than 9, long flashes are used for the tens and short flashes for the units. For example Fig. 2 shows one long flash, and three short flashes separated by a short pause, indicating trouble code 13.

Onboard diagnostic systems I (OBD-I)

In 1988 the California Air Resources Board (CARB) introduced legislation covering all new cars sold in California. These new laws governed on-board diagnostic requirements for emissions related faults and began the process of standardization in the US and eventually Europe.
These regulations were known as onboard diagnostic systems – phase I (OBD-I) and were subsequently adopted by the vehicle manufacturers, for states other than California.
The basic requirements of OBD-I were as follows:
- A malfunction indicator lamp (MIL), to provide a visible warning that an emissions related fault had been logged by the engine control module (ECM).
- Provision for the logging and storage, for subsequent retrieval, of diagnostic trouble codes (DTC)/flash codes for emissions related faults.
The location of the diagnostic socket, the method of access to the trouble codes and the configuration and scope of the self-diagnosis was left to individual vehicle manufacturers.
This resulted in an almost complete lack of standardization, requiring the technician to adopt different procedures and to use different equipment for each vehicle.

Onboard diagnostic systems II (OBD-II)

In 1995 the California Air Resources Board (CARB), after consultation with the Society of Automotive Engineers (SAE), introduced further legislation covering all new cars sold in California.
These regulations are known as OBD-II and have been adopted for all states. They closely define trouble code logging and retrieval. More significantly they require monitoring of the operation of the system and components, in addition to detecting component failures.
OBD-II also covers systems other than engine management.
Basically the US OBD-II regulations have been adopted by the International Organization for Standardization (ISO) for European vehicles and are known as EOBD – European On Board Diagnostics.
These EOBD regulations became mandatory for most new petrol engined vehicles produced after January 1st 2000 (diesel and LPG engined cars were not required to comply until 2003). Most petrol engined vehicles already in production before January 1st 2000 were granted exemption until January 1st 2001.

NOTE: The regulations mandate the use of SAE/ISO trouble codes for emissions related faults, e.g. Powertrain codes (‘P’ codes). However not all manufacturers conform to the SAE/ISO trouble codes for Body and Chassis faults, (‘B’ & ‘C’ codes) as they are not mandated. Some of these manufacturers use the same trouble code format as the SAE/ISO e.g. C0123, but they have definitions defined by the manufacturer.

EOBD codes

Basic requirements

Malfunction indicator lamp (MIL) located on the instrument panel, which either flashes or illuminates continuously, when a fault is detected. If no fault is present the MIL should illuminate when the ignition is switched on and extinguish when the engine starts.
Standard configuration of 16 pin data link connector (DLC) Fig. 3.
The 16 terminals of the DLC are arranged in two parallel rows, with certain terminals defined by the EOBD regulations and the remainder allocated by the vehicle manufacturer.

The terminals are assigned as follows:

NOTE: If ISO/SAE regulations are not used to provide on-board diagnosis (OBD) information, the assignment of the terminals 2, 6, 7, 10, 14 & 15 is left to the vehicle manufacturer.

Terminal	Assignment
1	Defined by vehicle manufacturer
2	Data bus (+) – SAE J1850
3	Defined by vehicle manufacturer
4	Chassis earth
5	Signal earth
6	CAN data bus, High – ISO 15765-4
7	K-line – ISO 9141-2/ISO 14230-4
8	Defined by vehicle manufacturer
9	Defined by vehicle manufacturer
10	Data bus (-) – SAE J1850
11	Defined by vehicle manufacturer
12	Defined by vehicle manufacturer
13	Defined by vehicle manufacturer
14	CAN data bus, Low – ISO 15765-4
15	L-line – ISO 9141-2/ISO 14230-4
16	Battery voltage

Standard location for the DLC

The standard location for the DLC is defined as being between the driver’s end of the instrument panel and 300 mm beyond the vehicle centre line, accessible from the driver’s seat.

The recommended location is between the steering column and the vehicle centre line.

Format of EOBD codes

5 character alpha-numeric trouble codes are made up as follows:

First character defines system group

B	Body
C	Chassis
P	Powertrain
U	Network communications

Second character defines code type

Body/chassis

0	SAE defined (EOBD)
1	Manufacturer defined
2	Manufacturer defined
3	For future allocation

Powertrain

0	SAE defined (EOBD)
1	Manufacturer defined
2	SAE defined (EOBD)
3	P3000-P3399 – Manufacturer defined, P3400-P3999 – SAE defined (EOBD)

Network communications

0	SAE defined (EOBD)
1	Manufacturer defined
2	Manufacturer defined
3	SAE defined (EOBD)

Third character defines system area

Powertrain – P0/P1 code

0	Fuel, air or emission control
1	Fuel or air
2	Fuel or air
3	Ignition system or misfire
4	Emission control
5	Vehicle speed, idle speed control or auxiliary inputs
6	Computer or auxiliary outputs
7	Transmission
8	Transmission
9	Transmission
A	Hybrid propulsion
B	Hybrid propulsion
C	Hybrid propulsion
D	For future allocation
E	For future allocation
F	For future allocation

Powertrain – P2 code

0	Fuel, air or emission control
1	Fuel, air or emission control
2	Fuel, air or emission control
3	Ignition system or misfire
4	Emission control
5	Auxiliary inputs
6	Computer or auxiliary outputs
7	Transmission
8	For future allocation
A	Fuel, air or emission control
B	Fuel, air or emission control
C	For future allocation
D	For future allocation
E	For future allocation
F	For future allocation

Powertrain – P3 code

0	Fuel, air or emission control
1	Fuel, air or emission control
2	Fuel, air or emission control
3	Ignition system or misfire
4	Cylinder deactivation
5	For future allocation
6	For future allocation
7	For future allocation
8	For future allocation
9	For future allocation
A	For future allocation
B	For future allocation
C	For future allocation
D	For future allocation
E	For future allocation
F	For future allocation

Network communications

0	Network electrical
1	Network communications
2	Network communications
3	Network software
4	Network data
5	Network data
6	For future allocation
7	For future allocation
8	For future allocation
9	For future allocation
A	For future allocation
B	For future allocation
C	For future allocation
D	For future allocation
E	For future allocation
F	For future allocation

The fourth and fifth characters define the specific fault.

These characters define general malfunction.

NOTE: Emissions related problems have a ISO defined list of codes and definitions starting with P0001.

Example code P0108

This code is logged when a high input is detected in the circuit of the manifold absolute pressure (MAP) sensor or barometric pressure (BARO) sensor.

P	System – Powertrain
0	Code type – SAE defined (EOBD)
1	System identification – Fuel and air
08	General malfunction – MAP/BARO sensor – circuit, high input

Failure type codes

All EOBD codes may have an additional two characters following the main trouble code which indicate the type of failure, e.g. P0351-XX, where ‘XX’ equals the failure type code.

Failure type codes are more commonly displayed using manufacturers’ diagnostic equipment and can be used in conjunction with all EOBD code types, ‘B’, ‘C’, ‘P’ & ‘U’.

Examples of failure type codes

EOBD code	Failure type
00	No failure type information
01	General electrical failure
07	Mechanical failure
08	Data bus signal/message failure
0A	General electrical failure 2
2A	Signal stuck in range
3A	Signal has too many pulses
49	Internal electronic failure
4A	Incorrect component installed
A3	System voltage high

Example: Trouble code P0351A3

This code is logged when the system voltage detected is high in the primary or secondary circuit of ignition coil A.

P	System – Powertrain
0	Code type – SAE defined (EOBD)
3	System identification – Ignition system or misfire
51	General malfunction – Ignition coil A, primary/secondary – circuit malfunction
A3	System voltage high

Hexadecimal codes

The EOBD trouble code is a hexadecimal number and therefore the third, fourth, fifth, sixth and seventh characters can be either a number (0-9), or a letter (A-F).

Unlike the decimal system that uses a base of 10, the hexadecimal system uses a base of 16. Using the characters 0-9 and A to F the number can be from 0-15.

Character	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
Value	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15

By using the hexadecimal system two characters can equate to a maximum number of 255. In the decimal system the maximum number with two characters is 99.

For example:

Hex	Decimal equation	Decimal
C8	(12 x 16) + (8 x 1)	200
FF	(15 x 16) + (15 x 1)	255
100	(1 x 16 x 16) + (0 x 16) + (0 x 1)	256

Standard areas monitored

The following areas are monitored continuously:

Misfire detection.
Fuel system performance.
Component performance.

The following areas are monitored once per ‘Trip’:

NOTE: The definition of a ‘trip’ varies, but is basically – key ON, vehicle driven, key OFF.

Catalytic converter
Evaporative emission system
Secondary air (AIR) system
Air conditioning system
Heated oxygen sensor (HO2S)
Oxygen sensor (O2S) heater
Exhaust gas recirculation (EGR) system
In cases where flash codes and EOBD codes are listed for the same model range, only one flash code will be generated for a particular component, but there may be a list of many EOBD codes related to this component. Alternatively there may be some EOBD codes with no equivalent flash code(s).
These EOBD codes will provide more specific details about the fault location, wiring, voltage signals and other information relative to the circuit or system.

Fault logging and drive cycles with EOBD

Fault logging is based on inputs received during each ‘trip’ which may comprise a number of ‘drive cycles’.
Each ‘drive cycle’ is initiated when the engine is started and is terminated when the engine is switched off.
For a complete ‘trip’ to be completed the following, complex, conditions need to be met (and may take several ‘drive cycles’ to complete):
- Before starting the engine, coolant temperature should be below 50°C and +/-6°C of ambient temperature.
  - This ensures that the ECM logs a cold start.
- Allow engine to idle for 2-3 minutes with an electrical load switched on (such as headlamps or heated rear window).
  - This will ensure that the misfire monitoring and fuel trim monitoring programmes run.
- Drive vehicle up to at least 50 mph and maintain this speed for at least 3 minutes.
  - Misfire and fuel trim monitoring will run.
- Allow the speed to reduce to around 20 mph without changing gear, using the brakes or the clutch.
  - Fuel trim monitoring will run.
- Accelerate to at least 50 mph and maintain for at least 5 minutes.
  - Misfire and fuel trim monitoring will run.
- Allow the speed to reduce to around 20 mph without changing gear, using the brakes or the clutch.
  - Fuel trim monitoring will run.
Each ‘trip’ starts when the engine is started and continues through a number of ‘drive cycles’ until all the EOBD monitors have completed a self-test.
The EOBD monitoring programme provides operating tolerance checks on all emissions related sensors and actuators. Some components/circuits are continuously monitored and some are only activated under predetermined operating conditions.
Misfire monitoring detects irregularities in the crankshaft position (CKP) sensor signal pattern and identifies which cylinder misfired and if the misfire is frequent enough to cause catalytic converter damage due to excess internal temperatures. If this is the case the MIL will flash.
If the misfire is likely to increase emissions above the EOBD limits and occurs on each of two consecutive ‘trips’ the MIL will flash. If the misfire is absent during the next three ‘trips’ the MIL will be extinguished.
When a trouble code is logged a number of data parameters are stored with it, to assist in accurate fault diagnosis. These are:
- Vehicle speed
- Engine coolant temperature
- Engine rpm
- Engine load
- Oxygen sensor system status – open/closed loop
- Distance since fault first logged
- Long term fuel trim (LTFT) level
Most EOBD scan tools are capable of capturing this ‘snapshot’ of data and displaying (or printing) it for analysis to aid the fault diagnosis process.

Fault logging and drive cycles with EOBD

EOBD monitoring is very sensitive and replacement components may still be identified as faulty if their specifications do not exactly match the originals.
The trouble code memory must be completely erased and a ‘trip’ completed.
The trouble code memory should be accessed to establish that no further codes have been logged.

DTC Terminology

Throughout this application the following standard descriptions and terminology have been used, together with J1930 component descriptions.

Left-hand (LH) and right-hand (RH) – As seen from the driver’s seat facing forward
Bank 1 – Cylinder bank or group including No. 1 cylinder (e.g. cylinders 1, 2 & 3 of a six cylinder engine)
Bank 2 – Cylinder bank or group not including No. 1 cylinder (e.g. cylinders 4, 5 & 6 of a six cylinder engine)
HO2S 1 – Heated oxygen sensor (HO2S) single or nearest to engine (before 1st catalytic converter)
HO2S 2 – Heated oxygen sensor (HO2S) after 1st catalytic converter
HO2S 3 – Heated oxygen sensor (HO2S) after 2nd catalytic converter
KS 1 – Knock sensor (KS) – Bank 1
KS 2 – Knock sensor (KS) – Bank 2