Retreiving codes on pre-OBD-II models:

  Drive the vehicle for five or more minutes ( on turbocharged vehicles the engine must exceed 3000 RPM's and 17 psi of boost ), and let it idle.  If the vehicle won't start, crank the engine for at least 6 seconds and leave the ignition switch turned on.  Now, proceed to the instructions below for your specific model.

1988-1990 models with 1984 cc engines:
  - On models with a diagnostic connector in the engine compartment ( next to the fuel distributor ), hook up the special Audi tester part number US1115 between the diagnostic connector and the positive battery terminal. ( On some models the diagnostic connector is in the fuse panel, on the fuel pump relay ).
 - To display a stored trouble code, install the spare fuse in the top of the fuel pump relay for 4 seconds. The tester will display the code.
  - Repeat this procedure to access each stored code.
  - To erase the codes, install the spare fuse and leave it in for at least 10 seconds.

1987 and 1988 models with turbocharged 2226 cc engine or 2309 cc engine:
   - Bridge the test contacts of the diagnostic trigger on the pump relay for 4 seconds. The MIL ( malfunction indicator lamp )will flash the code.  Repeat this procedure to access each stored code.

1989 - 1991 models with 2226 cc SOHC turbocharged engine ( one knock sensor ) or with 2309 cc engine:
  Hook up the special Audi tester part number US1115 or equivalent between the positive terminals of the dark-colored and the light-colored diagnostic connectors.
  - Using a jumper wire, bridge the negative terminals of the dark-colored and light-colored connectors for 4 seconds. The tester will display the code or, on California models the MIL will flash the code.
  - Repeat this procedure to access each stored code.

1990 and 1991 models with 2226 cc SOHC turbocharged engine ( 2 knock sensors )
  - Hook up the special audi tester between positive diagnostic terminals 1 and 3
  - Using a jumper wire, bridge negative terminals 1 and 2, the tester will display the code, or on California models the MIL will flash the code.
  - Repeat this procedure to access each stored code.

1990 and 1991 models with 3562 cc V-8 engines:
  - Bridge the upper terminals of diagnostic connectors 1 and 4 with the special Audi tester or equivalent,  crank the engine for 5 seconds, and leave the ignition switch on.
  - Using a jumper wire, bridge the lower terminals of diagnostic connectors 1 and 2. The test light or, on California models the engine light will flash the code.
  - Repeat this procedure to access each stored code,  after code 0000 has flashed, all stored codes have been displayed.

  Code definitions:

  CODE           DESCRIPTION

1111 : ECM
1119   Transmission range sensor
1213   Vehicle speed sensor
1231   Vehicle speed sensor
2111   RPM sensor
2112   Timing sensor
2113   RPM sensor
2114   Hall reference
2121   Idle switch
2122   Hall sender
2123   Throttle position switch
2132   Control unit
2141   Knock control
2142   Knock control
2143   Knock control
2144   Knock control
2212   Throttle valve
2214   RPM signal
2221   Vaccum control
2222   Pressure sensor
2222   Manifold vacuum
2223   Altitude sensor
2224   Manifold pressure
2224   Boos pressure
2231   Air mass sensor
2231   Idle stabilizer
2232   MAF sensor
2233   MAF sensor
2233   Reference voltage
2234   ECM
2234   System voltage
2242   CO sensor
2312   Engine coolant temperature
2314   Signal wire
2314   Transmission
2322   Intake air temperature
2324   MAF sensor
2331   Oxygen ratio
2332   Oxygen sensor II
2341   Oxygen sensor
2342   Oxygen sensor
2343   Fuel mixture
2344   Fuel mixture
2411   EGR system
2413   Mixture control
2413   Fuel pressure
3424   Fault lamp
4312   EGR system
4332   Ignition circuit
4343   EVAP canister purge
4411   Fuel injector 1 and 6
4412   Fuel injector 2 and 7
4413   Fuel injector 3 and 6
4414   Fuel injector 4 and 6
4421   Fuel injector no. 5
4422   Fuel injector no. 6
4423   Fuel injector no. 7
4424   Fuel injector no. 8
4431   Idle stabilizer
4433   Fuel pump
4442   Wastegate
4442   Boos pressure
4443   Canister purge
4444   No faults
0000   End diagnosis

16486   MAF sensor
16487   MAF sensor
16500   Coolante temperature sensor
16501   Coolant temperature sensor
16502   Coolant temperature sensor
16504   TP sensor
16505   TP sensor
16506   TP sensor
16507   TP sensor
16514   Oxygen sensor
16516   Oxygen sensor
16518   Oxygen sensor
16520   Oxygen sensor
16521   Oxygen sensor
16522   Oxygen sensor
16524   Oxygen sensor
16534   Oxygen sensor
16536   Oxygen sensor
16537  Oxygen sensor
16538   Oxygen sensor
16539   Oxygen sensor
16540   Oxygen sensor
16541   Oxygen sensor
16542   Oxygen sensor
16554   Fuel system
16555   Fuel system
16556   Fuel system
16557   Fuel system
16558   Fuel system
16559   Fuel system
16706   Engine speed sensor
16711   Knock sensor
16716   Knock sensor
16721   Crankcase sensor
16785   EGR
16786   EGR
16804   Catalyst system
16885   Speed sensor
16955   Cruise/brake switch
16989   Control module
17509   Oxygen sensor bank 1
17514   Oxygen sensor bank 2
17609   Injector no. 1
17610   Injector no. 2
17611   Injector no. 3
17612   Injector no. 4
17613   Injector no. 5
17614   Injector no. 6
17621   Injector no. 1 control circuit
17622   Injector no. 2 control circuit
17623   Injector no. 3 control circuit
17624   Injector no. 4 control circuit
17625   Injector no. 5 control circuit
17626   Injector no. 6 control circuit
17733   Knock sensor cylinder no. 1
17734   Knock sensor cylinder no. 2
17735   Knock sensor cylinder no. 3
17736   Knock sensor cylinder no. 4
17737   Knock sensor cylinder no. 5
17738   Knock sensor cylinder no. 6
17747   Crankshaft position/engine speed sensor
17748   Crankcase/camshaft signal
17749   Ignition amplifier no. 1 control circuit
17751   Ignition amplifier no. 2 control circuit
17753   Ignition amplifier no. 3 control circuit
17799   Camshaft position sensor
17800   Camshaft position sensor
17801   Ignition amplifier no. 1 control circuit
17802   Ignition amplifier no. 2 control circuit
17803   Ignition amplifier no. 3 control circuit
17808   EGR valve
17810   EGR valve control circuit
17815   EGR temperature sensor
17816   EGR temperature sensor
17817   EVAP canister purge regulator valve
17818   EVAP canister purge regulator valve
17819   Secondary air injection bank no. 2
17822   Secondary air injection bank no. 2
17828   Secondary air injection control valve
17830   Secondary air injection control valve
17831   Secondary air injection bank no. 1
17832   Secondary air injection bank no. 2
17842   Secondary air systemp pump relay
17844   Secondary air system pump relay
17908   Fuel pump relay circuit
17912   Intake system
17913   Throttle position switch
17914   Throttle position switch
17918   Throttle position switch
17919   Intake manifold change-over valve
17920   Intake manifold change-over valve
17978   ECM
18008   Low voltage at supply terminal
18020   ECM incorrectly coded.