How To: D8 2.1 Trip Computer Retrofit

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jonsowman
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How To: D8 2.1 Trip Computer Retrofit

Post by jonsowman » Fri Jan 13, 2012 8:54 pm

Hi all,

So after a while browsing forums and picking up parts and information, I decided to go for it today and retrofit a trip computer to my '98 2.1TD D8 406.

I know a few people have been looking to do the same, and yes it is possible!. Here's a guide :)

You'll need to get your hands on an MFD. I got one from an old D8 GLX that was being broken.

Now remove the coin try in your car -- just stick your hand in and pull it out. You'll notice a single connector mounted on its back. The trip computer has two rows of pins, however. The connector you already have goes into the top row of the trip computer. Read on to find out how to wire up the bottom row of pins...

The first issue is finding wire 1368, if it exists. This carries injection rate information from the Lucas EPIC ECU and is needed by the trip computer for mpg calculations. In some cars the lead won't exist at all, and you'll need to connect to pin 23 on the Lucas EPIC ECU. However, In some cars, like mine, it terminates in a brown connector under the steering wheel:

Remove the trim under the steering wheels and remove the connector:
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Try and locate wire 1368, on mine it was purple:
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It corresponds to this pin on the connector:
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I spliced a wire onto lead 1368 using a Scotchlok and pulled the wire up through to the trip computer opening in the centre console:
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The next issue is you'll need a button to switch between trip computer functions. I grabbed a replacement wiper stalk with the end button (new left, old right):
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I won't go into replacing the stalk itself, Haynes covers it and it's pretty straightforward.

The OEM loom has a lead (7205) leaving the wiper stalk connector (which is the one that connects to the function switch on the stalk) but I don't know where it goes. It was light blue cable on my car. I just Scotchloked another wire and pulled it through to the trip computer opening.

At this point I reconnected the brown under-steering-wheel connector and started the car up and checked all wiper functions were still as expected, and they were! So that's great, let's continue...

We need a tap onto leads 465 and 4310, both of which can be found on the yellow connector for the instrument panel. So out came the instrument panel...

Lead 4310 was blue on my 406, so pulled out another Scotchlok and hooked onto that:
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Secondly the speed interface tap, which is lead 465 from the Vehicle Speed Interface module to the instrument cluster. This was grey on my car, again on the yellow panel connector. You can guess what I used to splice onto it!
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Once you've got taps onto leads 4310 and 465, I added a couple of cable ties for tidyness and then replaced the instrument panel.

The final thing you'll need is an earth. I took mine from pin 2 (green/yellow wire) on the clock module:
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OK great! You'll now have 5 wires that you've pulled through to the trip computer orifice. Time to make up the connector. I got an old connector from a non-t/c D8, which was meant to be for the top row of pins. I had to do some trimming of plastic with a Stanley knife so it would fit into the bottom row of pins on the trip computer. The bits to be trimmed will be very obvious when you come to it, and takes 10 seconds.

As I dismantled the connector, the press in IDC piece broke, so I resorted to soldering the pins. Solder them up as follows:

Bottom row trip computer connections:
Computer pin 2 - Earth
Computer pin 5 - Wire 7205 (Function change switch)
Computer pin 6 - Wire 4310 (Instrument panel)
Computer pin 10 - Wire 465 (Speed interface module)
Computer pin 12 - Wire 1368 (EPIC ECU injection rate information)

Now you should have a complete connector, like this:
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Plug the connector into the trip computer, and ensure your existing OEM top row connector is fully inserted.

Start your car up and go for a drive! You should see range, average speed, average mpg information after about half a mile of driving. Instantaneous mpg will be displayed very soon after you start moving.

Success! A fully functional trip computer in a 2.1TD.

I had to set my MFD to '2' on the dial on the side to get all functions working

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Gary406
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Re: How To: D8 2.1 Trip Computer Retrofit

Post by Gary406 » Fri Jan 13, 2012 9:05 pm

excellent work. some1 finally did it

will copy it to KB now :mrgreen:
2004 (04) Volkswagen Bora 1.9 TDi (100)

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