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.
2002 Lexus ES 300FACTORY OEM SERVICE PROCEDURE
Inspection Procedure
- Check the power door lock operation. If the operation is OK, go to the next step. If the operation is not good, go to POWER DOOR LOCKS, TRUNK LID & FUEL DOOR RELEASE article in DOOR LOCKS & ANTI-THEFT SYSTEMS.
- Check the DTC code. Check data monitor (for MANUAL UP/DOWN switch). Using a hand-held tester, check that the DTC B1221 is output when the switch is operated. Using DTC B1221, which is a code when any master switch is constantly turned on, the MANUAL UP/DOWN switch operation can be monitored. If there is an output of DTC B1221 when the switch is operated, the switch circuit can be considered normal. If there is an output of DTC B1221 when the manual UP/DOWN switch is ON or no output of DTC B1221 when the manual UP/DOWN switch is OFF, the switch circuit can be considered normal. If the results are OK, go to the next step. If the results are not good, replace the power window regulator master switch assembly. See POWER WINDOW MASTER SWITCH under REMOVAL & INSTALLATION.
- Confirm the remote control power window by operating the master switch. When the rear door does not operate by the master switch, go to the next step. When the passenger's door does not operate by the master switch, repair or replace the wiring harness or connector (D17-8 (MPX2) - F13-8 (MPX2) wiring harness).
- Check the continuity of the communication line. Disconnect the body ECU connectors B5 and B6. See CONNECTOR IDENTIFICATION . Inspect the continuity of each terminal of the driver side junction block and rear power window regulator switch connectors. See INSPECTING BODY ECU & REAR POWER WINDOW REGULATOR SWITCH CONTINUITY table. If the continuity is OK, replace the driver side junction block assembly. If the left hand rear side continuity is not good, repair or replace the B6-5 (MPX5) - R15-8 (MPX1) wiring harness or connector. If the right hand rear side continuity is not good, repair or replace the B5-1 (MPX4) - R16-8 (MPX1) wiring harness or connector.INSPECTING BODY ECU & REAR POWER WINDOW REGULATOR SWITCH CONTINUITY
Item Tester Connection Specified Condition Left Hand Rear Side B6-5 (MPX5) - R15-8 (MPX1) Continuity Right Hand Rear Side B5-1 (MPX4) - R16-8 (MPX1) Continuity
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.