1993 Lexus LS 400FACTORY OEM SERVICE PROCEDURE

Trouble Code Identification

TROUBLE CODE IDENTIFICATION (1)

Code Description
12  RPM Signal Circuit (No. 1)
13  RPM Signal Circuit (No. 2)
14
LS400  Ignition Signal Circuit
SC400  Ignition Signal
15
LS400  Ignition Signal Circuit
SC400  Ignition Signal
16  A/T Control Signal Malfunction
21  Main Oxygen Sensor Signal Left Or Right Bank
22  Engine Coolant Temperature Sensor Circuit
24  Intake Air Temperature Sensor Circuit
25  Air/Fuel Ratio Malfunction
26  Air/Fuel Ratio Malfunction
27
LS400  Sub-Oxygen Sensor Circuit
SC400  Sub-Oxygen Sensor Circuit
28  Main Oxygen Sensor Signal Left Or Right Bank
29
LS400  Sub-Oxygen Sensor Circuit
SC400  Sub-Oxygen Sensor Circuit
31
LS400  Airflow Meter Circuit
SC400  Airflow Meter Circuit
35  Barometric Pressure Sensor Circuit
41  Throttle Position Sensor (TPS) Signal & Sub-Throttle Position Sensor Signal
42  Vehicle Speed Sensor (VSS) Circuit
43 (2) Starter Signal
47  Throttle Position Sensor (TPS) Signal & Sub-Throttle Position Sensor Signal
51  Switch Condition Signal
52  No. 1 Knock Sensor Signal, Knock Control Signal & No. 2 Knock Sensor Signal
53  No. 1 Knock Sensor Signal, Knock Control Signal & No. 2 Knock Sensor Signal
55  No. 1 Knock Sensor Signal, Knock Control Signal & No. 2 Knock Sensor Signal
71 (3) EGR System Malfunction
78  Fuel Pump Control Circuit
(1) If diagnostic code displayed is not shown in this table, ECU is faulty.
(2) Code 43 sets if vehicle is push-started (normal).
(3) California models only.
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.