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ECU Fault Code, Output Test System 1986-88 5000 Turbo and Turbo Quattro, 1989-91 100, 1989-91 200 Turbo and Turbo Quattro including 20V
The 1986-91 Audi I5 Turbo engines have Engine Control Units equipped with a "self-diagnostic system". This system can test 13 input and 5 output system checks on the 1986-88 5000TQ and early 1989 200TQ. It will perform 17 input checks and 6 output system checks on the later dual knock sensor MC engine in the 1989-90 200TQ and 1989-91 200T. The 1991 200TQ vehicles with the 20V engine and Motronic Engine Control Unit can record 31 faults and perform 8 output checks. Anytime an engine problem is occurring, this Fault Code system should be used to first locate any system fault codes that have been recorded. If the vehicle starts:You should drive the car for a minimum of 5-10 minutes and raise the engine speed above 3000 RPM and ensure that the manifold pressure goes above 1.2 bar. You want the engine coolant temp to get above 80C, (176F). You should accelerate at full throttle in 3rd gear to exercise this diagnostic system correctly. If the vehicle does not start: Crank the engine with the starter for at least 5 seconds. NOTE: On the 1986-88 5000T/Q and early 1989 200T/Q, the ignition should not be turned off after doing this full throttle test road test or after the "No Start" cranking test is done, as the fault memory will be erased. After doing the road test or the "No Start" cranking test, proceed to the section below for reading any fault codes stored during this process. Fault Code Reading: 1986-88 5000 Turbo and Turbo Quattro, Early 1989 200 Turbo and Turbo Quattro This system uses the "Check Engine" light in the instrument cluster to indicate faults in the system during the fault code reading process.  This light is also referred to as the Electronic Ignition Warning Light in the owners manual.
ROAD TEST After conducting a road test for 5-10 minutes, where the engine is warmed up and the engine is run briefly at full throttle in 3rd gear above 3000 RPM with boost going above 1.0 bar, LEAVE THE ENGINE IDLING as the fault codes will be erased if the engine is shut off after the road test. NO START CONDITIONS: If the car will not start, but will crank over, you can check for any fault codes stored. Crank the engine for at least 5 seconds and then leave the ignition on. The procedure below can also be used for retrieving fault codes under no start conditions. To start the fault code reading sequence, Insert a spare fuse into the top of the fuel pump relay for four seconds and then remove the fuse. This starts the fault code sequence by bridging the contacts on the top of the fuel pump relay. These fuel pump relay fuse contacts are connected to pin 31 on the ECU and to ground. The Fuel Pump relay is located under the hood in the main fuse panel near the windshield on the drivers side. See illustration below:  The "Check Engine" warning light should come on whenever the fuse is inserted into the top of the fuel pump relay. NOTE:The fault code reading procedure will be canceled if the engine RPM is raised above 2000 or if the ignition is turned off. Each fault code consists of four groups of pulses. The exact sequence for each code is a start sequence of 2.5 seconds with the lamp on, and 2.5 seconds pause with it off. The codes then follow as a half-second pulse with the light on, separated by a half-second pause with the light off, with a larger pause of 2.5 seconds between each set of pulses. Example: If no fault codes are stored, code 4444 will be displayed by the ECU. The ECU will turn the "Check Engine" light on and off as follows after the fuse is inserted into the fuel pump relay for 4 seconds and then removed. Light on (2.5 sec), Light off (2.5 sec) Now here comes the code 4444 Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Code 2142 (knock sensor) would be displayed as follows: Blink, pause, Blink, (2.5 second pause) Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, (2.5 second pause) The sequence of displayed pulses will keep repeating until the system is stepped to the next fault code stored (if any) by bridging the contacts on the fuel pump relay again for 4 seconds. The lamp will blink "once" at 2.5 second intervals to indicate that the last error code has been read. Use a note pad to write down the fault codes as they are displayed and then check for the specific fault code description listed in the section below. Check the Bentley Manual for additional information. Output Tests: 1986-88 5000 Turbo and Turbo Quattro, Early 1989 200 Turbo and Turbo Quattro There is also an "output test" mode that will turn the ECU controlled fuel pump on and cycle the engine electrical solenoids on and off to verify they are working correctly. Some later vehicles use fuse #28 in the main fuse box to supply +12V to all of these solenoids, so this fuse should be checked if they are not operating. To activate the Output Tests, you must first turn on the ignition (Do not crank or start the engine) and then insert the spare fuse into the fuel pump relay for 4 seconds to start the output tests. Each component will make noise when it is turned on and off during these output tests. You can also place your hand on the component to feel whether it is being turned on and is operating during these tests.
Fault Code Reading 1989-90 200 Turbo Quattro, 1989-91 200 Turbo This procedure applies to the later 1989 200 Turbo and Turbo Quattros after VIN #KN038262 with dual knock sensors and the MAC14 ECU. It also applies to the 1990 200TQ and 1990-91 200 Turbo. The MAC14 ECU fault code system has a non volatile memory for storing the fault codes which means that they can be read later even if the car has been turned off after the road test. There should be three connectors grouped together underneath the drivers side dash, from left to right, they should be arranged as follows: One black, one brown and one blue.  These three connectors are used to access the diagnostic capabilities inside the ECU (Engine Control Unit). This is done with the ignition on or with the engine running using the factory VAG1551 or VAG1552 scan tool connected to these diagnostic connectors or by using a jumper wire connected for 4 seconds across the diagnostic connectors. The "Check" engine light in the instrument panel or a separate light bulb or LED is used to flash out the fault codes .  IMPORTANT DETAILS: This yellow "Check" engine light will normally come on when the ignition is turned on "if" the bulb is installed in the dash. The operators manual refers to this "Check" engine light as the "Emission Control System (ECS) malfunction Indicator Light." Some of the 200TQ's have no "check" engine light bulb installed in the dashboard assembly even though the circuitry is there. Normally this bulb is installed in-between the "Airbag" light and the "Door Open" warning light on the right side of the dash and as mentioned, this light should come on when the ignition key is first turned on. You can partially pull the dash console out on the right side and reach around and install this "Check" Engine light bulb. Use one of the regular dash light bulbs, 12 volt, 1.2 Watt that twists into place. If you do not have the light bulb installed in the dash, you will need to connect an LED or low wattage light bulb (12 volt, 1.2 Watt) across these diagnostic connectors in order for the ECU to blink this light so you can read out the fault codes. Vehicles produced for sale in California should have this "Check" Engine light bulb installed in the dash. Details on building the LED fault code light can be found at the bottom of this page. A short jumper wire is also required to initiate the diagnostic sequence. Each diagnostic connector has two terminals in it. They are arranged as follows:Black, Brown and then Blue  As mentioned, with the ignition on or with the engine idling, you activate the fault code system by connecting the jumper wire across the two terminals for four seconds and then remove the jumper, the ECU will then begin the sequence to blink out the fault codes via the instrument panel "Check" Engine light or by flashing the LED connected across the diagnostic connectors. In some cases if the ignition is on, but the engine is not running you may get a 2111 or 2112 (RPM and TDC sensors) because the engine is not turning. NOTE: The fault code reading procedure will be canceled if the engine RPM is raised above 2000 on the MC 10V engines or if the ignition is turned off for all models . Each fault code consists of four groups of pulses. The exact sequence for each code is a start sequence of 2.5 seconds with the lamp on, and 2.5 seconds pause with it off. The codes then follow as a half-second pulse with the LED light on, separated by a half-second pause with the LED light off, with a larger pause of 2.5 seconds between each set of pulses. Example:If no fault codes are stored, code 4444 will be displayed by the ECU flashing the LED. The ECU will flash the LED on and off as follows after the jumper wire is inserted into the connectors for 4 seconds and then removed. LED on (2.5 sec), LED off (2.5 sec) Now here comes the code 4444 Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Code 2142 (knock sensor) would be displayed as follows: Blink, pause, Blink, (2.5 second pause) Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, (2.5 second pause) The sequence of displayed pulses will repeat until the system is stepped to the next fault code stored (if any) by connecting the jumper wire across the connectors again for 4 seconds. The LED will blink once at 2.5 second intervals to indicate that the last error code has been read. Use a note pad to write down the fault codes as they are displayed and then check for the specific fault code description listed in the section below. Check the Bentley Manual for additional information. In my 1989 200TQ, I have permanently connected a momentary push button switch across the two jumper wire connections so that I only need to push this button to activate the fault codes. I ended up installing the "check" engine light bulb back in the dash to avoid having to use the LED connected under the dash. NOTE: If you connect an LED permanently across these diagnostic connectors, you will notice that the LED "glows" dimly all the time even with the ignition off. The LED glows dimly because a very small current is flowing from the ECU through the LED to the +12V supply when the LED is connected to the diagnostic connectors. This current flow is only 0.4 milli amps, (400 micro-amps), or stated another way, 0.0004 amps. It is probably better to install the Dash mounted "Check" Engine light bulb than to permanently connect the LED across the diagnostic connectors. NOTE: In some cases, on these later 1989-90 200TQ vehicles, if the "Check" Engine light bulb "is" installed in the dashboard, then inserting a spare fuse into the fuel pump relay fuse slot "may" initiate the fault code reading sequence as was done in the 1986-88 5000TQ vehicles. Some of the later 200TQ's may have a slightly different fuel pump relay which no longer has the fuse contacts installed. OTHER DETAILS: Fuse #21 supplies power to Pin 33 on the MAC14 ECU for maintaining the fault code memory. This fuse also supplies the +12V for the black fault code connector underneath the dash. Check this fuse #21, if the fault codes do not blink out using the LED. Fuse #28 supplies +12V to the CIS frequency valve, the Charcoal canister solenoid, the Waste Gate solenoid, the charcoal filter cut off valve. Check this fuse if these components are not operating correctly. FAULT CODE ERASING NOTE: You can remove fuse #21 for a few minutes to erase any stored fault codes in these vehicles. If you conduct the OUTPUT tests, the fault code memory will also be erased at the end of the procedure. NOTE: Fuse 28 is located under the hood in the fuse box on the "side" rail of the fuse panel perpendicular to the other fuses. These fuses on the side rail are NOT Spare fuses! The fuse may be underneath a small red cover with Motor - Moteur on top. Output Tests 1989-90 200 Turbo Quattro, 1989-91 200 Turbo There is also an "output test" mode that will enable the MAC14 ECU to turn the fuel pump on and also cycle the engine electrical solenoids on and off to verify they are working correctly. Fuse #28 supplies +12V to the ECU controlled solenoids, so check this fuse if they do not operate. To activate the Output Tests, you must first connect the LED and the jumper wire to short across the Fault Code Connectors as shown and THEN turn on the ignition to start the output tests. Remove the jumper wire after 4 seconds:
There should be three connectors grouped together underneath the drivers side dash, From left to right, they should be arranged as follows: One black, one brown and one blue (it may be white)
These three connectors are used to access the diagnostic capabilities inside the ECU (Engine Control Unit). This is done with the ignition on or with the engine running using the factory VAG1551 or VAG1552 scan tool or by using a jumper wire connected across the fault code connectors. The "Check" engine light in the instrument panel (dashboard) will blink out the fault codes. The operators manual refers to this "Check" engine light as the "Emission Control System (ECS) malfunction Indicator Light."If the "Check" engine light does not come on with the ignition key turned to the on position, then you may not have a bulb installed in the instrument panel. If this is the case, you can install a 1.2 Watt instrument panel light bulb with twist lock socket or use a low wattage (1.2 watt) light bulb or LED connected across the fault code connectors to blink out the fault codes. See "IMPORTANT DETAILS" below for information on installing this "Check" engine light bulb. Each fault code connector has two terminals in it. They are arranged as follows: One black, brown and blue connector
As mentioned, with the ignition key on or with the engine idling, you activate the fault code system by connecting the jumper wire across the two terminals for four seconds and then remove the jumper, the ECU will then begin the sequence to blink out the fault codes. In some cases if the ignition is on, but the engine is not running you may get a 2111 or 2112 (RPM and TDC sensors) fault code or 2234 (supply Voltage) fault code. NOTE: The fault code reading procedure will be canceled if the ignition is turned off. Each fault code consists of four groups of pulses. The exact sequence for each code is a start sequence of 2.5 seconds with the lamp on, and 2.5 seconds pause with it off. The codes then follow as a half-second pulse with the LED light on, separated by a half-second pause with the LED light off, with a larger pause of 2.5 seconds between each set of pulses. Example:If no fault codes are stored, code 4444 will be displayed by the ECU flashing the LED. The ECU will flash the LED on and off as follows after the jumper wire is inserted into the connectors for 4 seconds and then removed. LED on (2.5 sec), LED off (2.5 sec) Now here comes the code 4444 Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Code 2142 (knock sensor) would be displayed as follows: Blink, pause, Blink, (2.5 second pause) Blink, (2.5 second pause) Blink, pause, Blink, pause, Blink, pause, Blink, (2.5 second pause) Blink, pause, Blink, (2.5 second pause) The sequence of displayed pulses will repeat until the system is stepped to the next fault code stored (if any) by connecting the jumper wire across the connectors again for 4 seconds. The LED will blink once at 2.5 second intervals to indicate that the last error code has been read. Use a note pad to write down the fault codes as they are displayed and then check for the specific fault code description listed in the section below. Check the Bentley Manual for additional information. IMPORTANT DETAILS:This yellow "Check" engine light will normally come on when the ignition is turned on "if" the bulb is installed in the dash. The operators manual refers to this "Check" engine light as the "Emission Control System (ECS) malfunction Indicator Light." Some of the 200TQ's have no "check engine" light bulb installed in the dashboard assembly even though the circuitry is there. Normally this bulb is installed in-between the "Airbag" light and the "Door Open" warning light on the right side of the dash and this light should come on when the ignition key is first turned on. To install or replace the "Check" engine light bulb, remove the instrument panel lower trim piece and remove the screws holding the instrument panel. Now you can partially pull the instrument panel out on the right side and reach around and install this twist lock light bulb. Use one of the clear instrument panel illumination light bulbs, 12 volt, 1.2 Watt with the twist lock plastic base socket. If you do not have the light bulb installed in the dash, you will need to connect an LED or low wattage light bulb (12 volt, 1.2 Watt) across these diagnostic connectors in order for the ECU to blink this light so you can read out the fault codes. Vehicles produced for sale in California should have this "Check Engine" light bulb installed in the dash. FAULT CODE ERASING Fuse #27 supplies power to pin 18 of the Motronic ECU for maintaining the fault code memory. You can remove this fuse #27 for a minute or so to erase any stored fault codes. Fuse #21 supplies the +12V for the black fault code connector underneath the dash as well as the +12V for the Turbo after run coolant pump. Check this fuse #21, if the fault codes do not blink out using the LED. NOTE: The 1991 200TQ 20V engine also has fuse #13 (15Amp) for the fuel pump, fuse #28 (15A) which supply +12V to the fuel injectors and fuse #24 (10A) which supplies +12V to the Waste Gate Frequency Valve, the Idle Stabilizer Valve and the Carbon Canister Valve. Fuse #29 supplies +12V to the O2 sensor heating element on this vehicle as well. If fuse #13, #27, or #28 gets blown.... the engine will not run! The 6 Fuses, #24 to 29 are located under the hood in the fuse box on the "side" rail of the fuse panel perpendicular to the other fuses #1-21. These fuses on the side rail are NOT Spare fuses! Fuses 27 and 28 may be under a small red plastic holder with Motor - Moteur written on top. In my 1989 200TQ, I have permanently connected a momentary push button switch across the two jumper wire connections so that I only need to push the button to activate the fault codes. In my 1989 200TQ, I ended up installing the "check" engine light bulb back in the instrument panel so I did not have to connect the LED across the fault code connectors under the dash. NOTE: When you connect an LED across these diagnostic connectors, you will notice that the LED "glows" dimly all the time with the ignition off. The LED glows dimly because a very small current is flowing from the ECU through the LED to the +12V supply when the LED is connected to the diagnostic connectors. This current flow is only 0.4 milli amps, (400 micro-amps), or stated another way, 0.0004 amps. It is probably better to install the Dash mounted "Check Engine" light bulb than to permanently connect the LED across the diagnostic connectors. Output Tests 1991 200 Turbo Quattro with 20V Engine There is also an "output test" mode that will cycle the engine electrical solenoids on and off to verify they are working correctly. Fuse #28 supplies +12V to the ECU controlled fuel injectors, and fuse #24 supplies +12V to the Idle Stabilizer Valve, the Carbon Canister Valve, and the Waste Gate Frequency valve, so check these fuses if you suspect a problem with the operation of these components. To activate the Output Tests, you must first connect the Jumper Wire across the Fault Code Connectors as shown in the above diagram and THEN turn on the ignition to start the output tests. Remove the jumper wire after at least 4 seconds. NOTE: The LED should also be connected so you can see the output test codes blink out, but it does not "have" to be connected to initiate the Output tests.
(one black and one brown, same location, under the driver side dash). This photo shows three similar connectors used in the 200 Models. IMPORTANT DETAILS: This yellow "Check" engine light will normally come on when the ignition is turned on "if" the bulb is installed in the dash. The operators manual refers to this "Check" engine light as the "Emission Control System (ECS) malfunction Indicator Light." Some of the Audi 100's have no "check engine" light bulb installed in the dashboard assembly even though the circuitry is there. Normally this bulb is installed in-between the "Airbag" light and the "Door Open" warning light on the right side of the dash and this light should come on when the ignition key is first turned on. If you do not have the light bulb installed in the dash, you will need to connect an LED or low wattage light bulb (12 volt, 1.2 Watt) across these diagnostic connectors in order for the ECU to blink this light so you can read out the fault codes. Vehicles produced for sale in California should have this "Check Engine" light bulb installed in the dash. The documentation for the 100 shows a black and brown connector, but no blue connector. Connect the LED positive terminal (LED's are polarity sensitive) to the top black terminal, and the negative LED terminal to the bottom terminal in the brown connector as shown.  Use a jumper wire between the bottom black connector terminal and the same bottom terminal in the brown connector to short for 4 seconds then remove jumper, to initiate the fault codes (ignition key on, with or without the engine running). Check the Bentley Manual for additional information. LED "Test Light" Construction, for blinking out fault codes. (1989-91 200TQ/100) The LED with a series resistor is normally connected across two terminals on the fault code connectors. The LED normally needs a resistor in series to limit the current, most LED's operate with 10-30 milli-amps (0.010 to 0.030 amps). A 1/4 watt 680 ohm resistor works pretty well but you don't have to use a resistor with exactly 680 ohms. The current that is flowing through the LED test light circuit is calculated as follows: Charging system voltage minus voltage drop across LED, divided by the resistance (14 Volts - 1.2 Volts)/680 = 18.8 milli-amps (0.0188 amps). The lower the value of resistance, the more current that flows and the brighter the LED, up until the point the smoke gets out. Radio Shack should have the necessary components to build this LED test light.There are some newer "Super bright" LED's that some electronic supply houses carry that should work great in this application. Here is a diagram that illustrates the connection of the resistor in series with the LED. I normally use two different colored. wires (black/red) as the LED is polarity sensitive, the flat section on the LED lamp is normally the negative connection. Bolt lug terminals (U shaped) with one leg trimmed off, can be crimped on the wire ends to allow easy insertion into the fault code connector terminals. It won't hurt it if you connect the LED backwards, it just won't make any light.....the resistor can be connected in series on either the + or - wire to the LED. Fault Code Listing NOTE: The fault codes shown below indicate that the ECU has recorded a problem with one or more of the following: A system component, the wiring, the wiring connections, or from a engine mechanical problem (vacuum leak, low compression, etc.). If you get multiple fault codes recorded, step through the fault code reading sequence and write down all the fault codes that were recorded. After you locate the source of the problem for the "first" fault code you read, you may want to then clear all the fault codes stored and drive the car again to see if the other fault codes are stored again. In some cases multiple fault codes are recorded even though there may be only one problem with the system. Code Number Source of Fault code Possible cause Recommended Check or Repair Symptom in some cases
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