UART Communication Line Circuit Inspection

WARNING: This page is about a different car, the 2007 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.

CHECK UART LINE INPUT/OUTPUT SIGNAL 1

Turn ignition switch OFF.

Check signal between driver seat control unit connector and ground, with oscilloscope.

TERMINALS SIGNAL REFERENCE

Connector	Terminals		Condition	Signal
Connector	(+)	(-)	Condition	Signal
B401	17	Ground	Pedal adjusting switch ON (FORWARD or BACKWARD operation)	Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

OK: GO TO 2.

NG: Check the following.

When voltage wave form does not appear with a constant voltage (approx. 5V), replace driver seat control unit.
When voltage wave form does not appear with a constant voltage (approx. 0V), replace automatic driver seat control unit.

Fig 1: Checking Signal Between Driver Seat Control Unit Connector Terminal 17 And Ground
Courtesy of NISSAN MOTOR CO., U.S.A.

CHECK UART LINE INPUT/OUTPUT SIGNAL 2

Check signal between automatic drive positioner control unit connector ground, with oscilloscope.

TERMINALS SIGNAL REFERENCE

Connector	Terminals		Condition	Signal
Connector	(+)	(-)	Condition	Signal
M41	10	Ground	Pedal adjusting switch ON (FORWARD or BACKWARD operation)	Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

OK: GO TO 3.

NG: Check the following.

When voltage wave form does not appear with a constant voltage (approx. 5V), replace automatic drive positioner control unit.
When voltage wave form does not appear with a constant voltage (approx. 0V), replace driver seat control unit.

Fig 2: Checking Signal Between Automatic Drive Positioner Control Unit Connector Terminal 10 And Ground
Courtesy of NISSAN MOTOR CO., U.S.A.

CHECK UART LINE HARNESS
1. Disconnect driver seat control unit and automatic drive positioner control unit.
2. Check continuity between driver seat control unit connector B401 terminals 1, 17 and automatic drive positioner connector M41 terminals 10, 26.
  1 - 10 : Continuity should exist.
  
  17 - 26 : Continuity should exist.
3. Check continuity between driver seat control unit connector B401 terminals 1, 17 and ground.
  1 - Ground : Continuity should not exist.
  
  17 - Ground : Continuity should not exist.
  
  Fig 3: Checking Continuity Between Driver Seat Control Unit Connector B401 Terminals 1, 17 And Ground, And Between Connector B401 Terminals 1, 17 And Automatic Drive Positioner Connector M41 Terminals 10, 26
  Courtesy of NISSAN MOTOR CO., U.S.A.
OK or NG

OK: GO TO 4.

NG: Repair or replace harness.
CHECK DRIVER SEAT CONTROL UNIT
Does the automatic drive positioner operate when the driver seat control unit is exchanged?

OK or NG

OK: Replace driver seat control unit.

NG: Replace automatic drive positioner control unit.