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.
1994 Lexus ES 300FACTORY OEM SERVICE PROCEDURE
Normal Mode
- Connect scan tester to Data Link Connector (DLC) No. 3 located in fuse block on lower left side of dash. See Fig 1.
- Turn ignition on with engine off. Turn scan tester on. When using Lexus scan tester, ensure scan tester is in Normal Mode.NOTE: When using Lexus scan tester, when scan tester is switched from Normal Mode to Check Mode, all trouble codes and freeze frame data will be erased. DO NOT switch modes until all trouble codes and freeze frame data are recorded.
- Using scan tester manufacturer's instructions, check for trouble codes and freeze frame data. If scan tester displays UNABLE TO CONNECT TO VEHICLE, the DLC No. 3 must be checked. See DLC NO. 3 INSPECTION under SCAN TESTER PROBLEMS. If scan tester does not display UNABLE TO CONNECT TO VEHICLE, proceed to next step.
- Record any trouble codes and freeze frame data displayed for system diagnosis. Freeze frame data records engine conditions when a misfire (Trouble Codes P0300-P0306), fuel trim malfunction (Trouble Codes P0171-P0172) or other malfunctions are detected. Freeze frame data such as fuel system conditions, engine coolant temperature, engine speed and vehicle speed etc. are recorded when malfunction exists. Information may be useful for determining conditions in which the malfunction occurs.NOTE: When using OBD-II scan tester, ignition must be turned off and back on. Procedure must be followed to record trouble codes with Two Trip Detection Logic. For information on Two Trip Detection Logic, see NOTES ON TROUBLE CODES .
- When using OBD-II scan tester, turn ignition off and then back on. Record any other trouble codes and any freeze frame data displayed for system diagnosis. On all applications, after trouble codes are retrieved, turn scan tester and ignition off.
- For trouble code detecting conditions and trouble code identification, see TROUBLE CODE DETECTING CONDITIONS and TROUBLE CODE IDENTIFICATION tables.
- To repair failure causing trouble code, refer to appropriate code in TROUBLE CODE IDENTIFICATION table. Once repairs for trouble code are made, trouble code must be cleared from ECM memory. See CLEARING TROUBLE CODES .
Factory Service Tools
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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.