Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1990 Lexus LS 400FACTORY OEM SERVICE PROCEDURE
Engine Controls - Tests W/O Codes
- Introduction
- LS400 Diagnosis By Symptom
- Does Not Start
- Difficult To Start
- Poor Idle
- Poor DRIVEABILITY
- Engine Stall
- Poor Fuel Economy
- LS400 Diagnosis By Symptom (Transmission)
- Vehicle Does Not Move In Any Gear Selection
- Vehicle Does Not Move In A Particular Gear Selection
- NO UPSHIFT 1ST To 2ND
- No Upshift 2ND To 3RD
- NO UPSHIFT 3RD To O/D
- NO DOWNSHIFT O/D To 3RD
- NO DOWNSHIFT 3RD To 2ND
- NO DOWNSHIFT 2ND To 1ST
- No Lock-Up
- No Lock-Up Off
- Shift Point Too High Or Too Low
- Upshifts To 2ND Or 3RD While In L Range
- Upshifts To O/D From 3RD While O/D Switch Is Off
- Upshifts To O/D From 3RD While Engine Is Cold
- Harsh Engagement
- Slip Or Shudder
- No Engine Braking
- Poor Acceleration
- No KICKDOWN
- Large Shift Shock Or Engine Stalls When Starting Off Or Stopping
- Intermittent Problem Diagnosis
- Test Procedures
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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