Faulty electronic speedo. How can I repair it?

Question edited for clarity.
Question moved to model category.

GMC Sierra mk1 (1996 - 1998) - fuse box diagram

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Jan 12, 2017 - GMC Sierra mk1 (1999 - 1998) - fuse box diagram. Year of production: 1996, 1997, 1998. Instrument Panel Fuse Block. The fuse block access ...

Fuse Box Diagram Chevrolet

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Fuse box diagram (location and assignment of electrical fuses and relays) for Chevrolet (Chevy) Astro (1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, ...

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  Chevrolet Suburban (GMT400; 1993-1999) fuses and relays

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  Fuse box diagram (location and assignment of electrical fuses and relays) for Chevrolet (Chevy) Suburban (GMT400; 1993, 1994, 1995, 1996, 1997, 1998, 1999).

Door lock problems are a known issue

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Depending if it is a cable type speedo or a electronic type speedo . you can disconnect a cable type to see if the cable turns which it will turn many times in a normal city block if it is functioning normally and if so this might indicate a faulty speedo . A electronic speedo can be checked to see if it is receiving power to it by the use of a multi meter

The 1998 TDI uses an electronic speedo. Assuming all the other gauges on the dash are working, then it is not a blown fuse. In this case it is either the pick up from the gearbox, the speedo itself or the wiring in between. The easiest way to check is by substitution of the speedo or the pick up one at a time. If this fixes it then the wiring is OK. If it doesn't fix it, then go looking for a wiring fault. Given the age, the wiring behind the dash can fail either by open circuit or shorting, so I usually just run new wires if I get a fault in one.

Start off buy checking speedo sensor or cable

You cannot interchange these speedo clusters as they are coded to the vehicle ECU. The only way to repair the failed LCD display (a common problem) is to incur the exorbitant cost of a new unit installed and coded by the dealers. I have had electronics "experts" strike out in the past so if someone else has a solution I stand to be corrected!

Sorry- not what you wanted to hear!

I would suspect you have a faulty electronic speedo head, have the cluster removed and have it sent out for repair of the problem. There is no at home repair procedure for this problem, it takes special equip to repair the speedo.

98 tdi has electronic speedo and the most likley fault is the speed sensor on the transfer box just infront of the handbrake drum on the lefthand side it is held in by a 10mm headed bolt

More likely to be the speedo drive in the transmission or a faulty speed sensor that is electronic i would be guessing here as 98 was the change over year for civic so it depends which transmission is fitted. Don't rip the dash to pieces just yet as i'm guessing this will just create more trouble. Steve Baldam in the UK

Speedometer gearing damaged or speed sensor problem. It is electronic (no cable).
Since it works intermittantly, I would tend to lean toward the speedo. This may require a swap of the entire cluster.