Wiring Information - B5 1.8T

[Grant620]

Hi Guys,
Can anyone assist with a technical question about ECU wiring on an Audi A4 B5 1.8T (99 MY)
On the ECU there are two wires that I don't seem to be able to work out the function of:
Pin 5 - Green / Black
Pin 18 - Yellow
Also, on the Instrument Cluster, blue plug, Pin 16 is meant to be the MIL / CEL Light, but the loom is empty at the connector. Does the CEL light get a signal from a different wire?

Any help would be massively appreciated.

[FrenchAudi]

According to diagrams in my Bentley manual.
Pin 5 (gn/bk) goes to pin 35 on the TCM (Transmission control module)
Pin 18 (y) is noted as being for ACS and Trip Computer only, and goes to T10y/1 (Wire connector, 10 point, blue, connector station, electronics box in plenum chamber.
and T20/1 on J189 (ACS and Trip Computer only). J189 is identified on another diagram as Auto Check System.

T32 - Wire Connector, 32 Point, blue, which I think is the plug you refer to on the Instrument Cluster, has a yellow/brown on Pin 16 (which goes to K18 - Trailer Operation Indicator Light). The y/br wire is from track number 51, which shows it connected to Pin 17 on J220, the Motronic ECM.

I hope this is of some help. I find these diagrams I have very confusing, covering so many different versions of the A4 in only 6 years with 2 different engines.

It's easy to see why CAN bus became essential!

[Grant620]

Thanks for that.
Interesting... So any idea what the ECU puts out on Pin 18?

I don't have any wires on Pin 17 of the J220.

[FrenchAudi]

Thanks for that.
Interesting... So any idea what the ECU puts out on Pin 18?

Sorry, I don't know. The book diagram only shows where the wires go, not what's inside the magic boxes.

[arman123]

found this online for instrument cluster

Pin assignment at multi-pin connectors on instrument cluster - vehicles from model year 1998

Multi-pin connector, 32-pin, blue 1 - Terminal 15 2 - Turn signal (right-side) 3 - Speedometer output 1 4 - Not used 5 - Fuel gauge sender 6 - Airbag 7 - Terminal 31 (sensor earth) 8 - Coolant temperature 9 - Terminal 31 (load earth) 10 - Oil pressure switch 11 - Engine speed signal 12 - Terminal 61 13 - Glow period warning lamp or CAT 14 - Self-levelling suspension 15 - Terminal 58d 16 - Trailer turn signal / fault in engine electrical system 17 - Main beams 18 - Turn signal (left-side) 19 - ABS 20 - Terminal 58s 21 - Door contact, driver's side 22 - Coolant level low 23 - Terminal 30 24 - Terminal 31 (load earth) 25 - K wire 26 - Right parking light 27 - Left parking light 28 - Speedometer input 29 - Brake fluid level/pressure 30 - S contact 31 - Belt buckle 32 - ESP