1990 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Normal Mode

  1. Normal Mode is used for routine testing of vehicle. Turn ignition switch to the ON position, but do not start engine. Turn O/D switch on. Using a jumper wire, connect terminals TE1 and E1 at TDCL or check connector. See Figure. Read the trouble codes as indicated by the number of flashes of O/D OFF light.
    NOTE: If O/D OFF light will not flash, refer to O/D SWITCH & O/D OFF LIGHT CIRCUIT chart.
  2. If no transmission trouble codes are present, the light will blink continuously 2 times per second. Trouble code flashes will be at the rate of one flash per second with longer pauses separating digits and codes. Refer to LS400 AUTOMATIC TRANSMISSION CODE IDENTIFICATION table. Refer to appropriate transmission diagnostic chart. For location of transmission components, see Figure.
  3. If a malfunction is encountered with transmission and no diagnostic codes are set, refer to LS400 DIAGNOSIS BY SYMPTOM (TRANSMISSION). To clear codes, see CLEARING CODES in this article.
NOTE: If both speed sensors No. 1 and No. 2 fail simultaneously, no diagnostic code will be set and fail-safe system will not function. After this occurs, when driving in D range, transmission will not upshift from first gear, regardless of vehicle speed.
LS400 AUTOMATIC TRANSMISSION CODE IDENTIFICATION

Code Signal Affected
N/A (1) Normal
42  Speed Sensor No. 1 Signal
46  Solenoid Valve No. 4 Signal
61  Speed Sensor No. 2 Signal
62  Solenoid Valve No. 1 Signal
63  Solenoid Valve No. 2 Signal
64  Solenoid Valve No. 3 Signal
67  Overdrive Direct Clutch Speed Sensor Signal
68  Kickdown Switch Signal
(1) O/D OFF light will blink 2 times every second.
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.