Querying the memory device for fault codes (VW Passat B3)

Mono-Jetronic, Mono-Motronic up to 9/93

The electronics of the control unit allow faults in the injection system to be detected. After the first occurrence of faults, their codes are stored in the memory device. At the same time, a signal light comes on on the instrument panel, which shows that a fault code has been received in the memory device. Even if a fault occurs only once, for example, due to a loose contact, its code is also stored in the memory device.

Output of fault codes in the form of a sequence of light pulses

The fault code memory is queried by connecting the VAG diagnostic tester to the plug located under the bellows in front of the gearshift lever. Please refer to the instructions in the diagnostic tester manual.

If a diagnostic tester is not available, interrogating the memory for fault codes from 4/89 can also be done using a semiconductor diode lamp.

Check fuse #18 in the fuse box and replace if necessary.



Connect a semiconductor diode lamp, such as VAG 1527, as shown in the figure, to the test sockets -A- (black) and "B" located in the footwell on the driver's side (brown).



Start the engine and let it idle. When interrogating the memory device, do not give gas, otherwise the code in the form of a sequence of light pulses will be erased.

Note: If the engine does not start due to faults in the injection system, turn on the starter for about 6 seconds. Without turning off the ignition after this, interrogate the memory device.

Connect auxiliary plugs "C" and "D" for at least 5 seconds and disconnect again. The LED should start flashing.

Each code in the form of a sequence of light pulses consists of four groups of light pulses. Between the groups of light pulses there are pauses of approximately 2.5 seconds.

Fault codes are read by determining the number (quantities) light pulses within each group.

Read the fault code as a sequence of light pulses and write it down. If the sequence of light pulses is 44-4-4, then the memory device does not contain fault codes and the check is complete.

If a fault code is issued, it should be written down. Continue the fault code reading process until the code 0-0-0-0 appears (END of code issuance - ENDE). To repeat the code reading process, either insert the fuse in the fuel pump relay for at least 5 seconds, or connect the "C" and "D" plugs for at least 5 seconds.

Using the table of fault codes, identify the fault and eliminate it.

Clearing the contents of the memory for fault codes

Turn off the ignition.

Connect plugs "C" and "D".

Turn on the ignition and leave it on for at least five seconds. This will erase the fault codes in the memory device.




The original text can be found at (VWMANUAL)