Audi OBD1 1991-1996 Idiot Light Diagnostic Guide without OBD Scanner

Audi OBD1 Idiot Light Diagnostic Guide without OBD Scanner

General information

• Trouble codes are displayed by using an LED connected to the data link connector (DLC).
• The ECM fault memory can also be checked and erased using diagnostic equipment connected to the data link
  connector (DLC).
• Self-diagnosis using flash type trouble codes may not display all available diagnostic information.
• Carry out road test for 10 minutes.

Accessing

• Ensure ignition switched OFF.
• Bridge black data link connector (DLC) terminal 1 Fig. 1 [A] and brown or white data link connector (DLC) terminal 1 Fig.
• 1 [B] with a switched lead – contacts normally open.
• Connect LED test lamp between black data link connector (DLC) terminal 2 Fig. 1 [A] and ECM terminal 33.
• 80: ECM located behind the passenger’s glovebox.
• 100: ECM located in the plenum chamber.

NOTE: DO NOT disconnect ECM multi-plug as this will erase fault memory.

• Start engine. Allow to idle.

NOTE: If engine does not start: Crank engine for 6 seconds. Leave ignition switched ON.

• Operate switch for 4 seconds.
• Release switch. Check that LED flashes.
• Count LED flashes. Note trouble code.
• Each trouble code consists of four groups of one to four flashes.
• A 2,5 second pause separates each trouble code group Fig. 2 [A].
• Repeat switch operation. Note trouble codes. Compare with trouble code table.
• End of test sequence indicated by trouble code 0000 (long flashes).
• Switch ignition OFF. Rectify faults as necessary.

Erasing Codes

Method 1

• Ensure ignition switched OFF.
• Bridge black data link connector (DLC) terminal 1 Fig. 1 [A] and brown or white data link connector (DLC) terminal 1 Fig. 1 [B] with a switched lead – contacts normally open.
• Operate switch and hold.
• Switch ignition ON.
• Release switch after 5 seconds.
• Repeat checking procedure to ensure no data remains in ECM fault memory.

Method 2

• Ensure ignition switched OFF.
• Disconnect ECM multi-plug or battery earth lead.

NOTE: ECM adaptive memory may be erased causing erratic running faults. Carry out road test to allow ECM to relearn basic values.
WARNING: Disconnecting the battery may erase memory from electronic units (e.g. radio, clock).

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