Inspection Procedure

WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.

CHECK DIAGNOSTIC TROUBLE CODE (A ECU)
1. Check whether outputs of diagnostic codes will stop when A ECU connector is disconnected.
  
  Fig 1: Diagnostic Codes (A ECU) Circuit Diagram
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  
  NOTE: Disconnect the connectors in the operational sequence, and start the next operation after the connector is connected.
  
  HINT:
  
  In this case, A ECU represents the power window regulator master switch assy (driver door ECU).
  
  Standard: If outputs of diagnostic codes stop, A ECU is abnormal.
OK: REPLACE A ECU

NG: Go to next step.
CHECK DIAGNOSTIC TROUBLE CODE (B ECU)
1. Check whether outputs of diagnostic codes will stop when B ECU connector is disconnected.
  
  Fig 2: Diagnostic Codes (B ECU) Circuit Diagram
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
NOTE: Disconnect the connectors in the operational sequence, and start the next operation after the connector is connected.

HINT: In this case, B ECU represents the power window regulator switch assy (passenger door ECU).

Standard:

If outputs of diagnostic codes stop, either B ECU or the wire harness between A ECU and B ECU is abnormal.

NG: Go to step 4

OK: Go to next step.
CHECK WIRE HARNESS BETWEEN A ECU AND B ECU
Inspect short-circuit in +B or body ground.

Fig 3: Diagnostic Codes (A And B ECU) Circuit Diagram
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Check whether a diagnostic code will be output when A ECU connector is connected.
NOTE: Disconnect the connectors in the operational sequence, and start the next operation after the connector is connected.

OK: REPLACE B ECU

NG: REPAIR OR REPLACE WIRE HARNESS BETWEEN A ECU AND B ECU
CHECK WIRE HARNESS MPX BODY ECU AND A ECU OR B ECU
1. Inspect short-circuit in +B or body ground.
  1. Disconnect the connector of A ECU and body ECU.
  2. Inspect short-circuit in +B of the wire harness between A ECU and body ECU, and also short-circuit in the body ground.
    
    Fig 4: MPX Body ECU And A ECU Or B ECU Circuit Diagram
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    
    Standard:
    
    0 V when short-circuited in +B.
    
    No continuity exists between each ECU and the body ground when short-circuited in the body ground.
    
    HINT:
    
    In this case, A ECU represents the power window regulator master switch assy (driver door ECU).
  3. Inspect short-circuit in +B of the wire harness between B ECU and driver side J/B (body ECU) and also short-circuit in the body ground.
    Standard:
    
    0 V when short-circuited in +B.
    
    No continuity exists between each ECU and the body ground when short-circuited in the body ground.
    
    HINT:
    
    In this case, B ECU represents the power window regulator switch assy (passenger door ECU).
    
    NG: REPAIR OR REPLACE WIRE HARNESS BETWEEN MPX BODY ECU AND A ECU OR B ECU
    
    OK: REPLACE DRIVER SIDE JUNCTION BLOCK ASSY