1994 Lexus SC 400FACTORY OEM SERVICE PROCEDURE

Speedometer System Test

  1. If odometer does not operate, go to next step. If odometer operates, check trip meter operation. If trip meter does not operate, go to step 4). If trip meter operates, replace speedometer.
  2. Disconnect connector "C" from back of instrument cluster. See Figure. Raise and support vehicle with rear wheels off of ground. Turn ignition on. At harness side of connector "C", connect voltmeter between terminals No. 13 and 15. See Figure. Turn ignition on. Rotate drive shaft.
  3. If voltage alternates between zero and 11 or more volts for each revolution of drive shaft, replace circuit plate. See Figure. If voltage does not alternate between zero and 11 or more volts, check VSS. See VEHICLE SPEED SENSOR (VSS) TEST  under COMPONENT TESTING. If VSS is okay, repair circuit between VSS and instrument cluster.
  4. Disconnect connector "C" from back of instrument cluster. See Figure. At harness side of connector "C", connect a jumper wire to terminal No. 1. See Figure. Connect other end of same jumper wire to corresponding terminal on instrument cluster side of connector "C".
  5. In the same manner, connect 3 other jumper wires between terminals No. 13, 15 and 23. This simulates an attached connector, but with only 4 wires connected.
  6. Raise and support vehicle with rear wheels off of ground. Turn ignition on. Connect voltmeter between terminals No. 13 and 15 of disconnected connector. Rotate drive shaft. If voltage alternates between zero and 11 or more volts for each revolution of drive shaft, replace speedometer. If voltage does not alternate between zero and 11 or more volts, replace circuit plate. See Figure.
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.