Navigation System Symptom Troubleshooting - Display unit buttons do not work

Display unit buttons do not work
NOTE: Always check the connectors for poor connections or loose terminals.
  1. Turn the ignition switch to ACC (I).
  1. Measure the voltage between body ground and display unit 20P connector terminal No. 1 and No. 2 individually.
Is there battery voltage?
YES -
Go to Step 3 .
NO -
If the +B wire does not have voltage, repair the open in the wire between the passenger's under-dash fuse/relay box and the display unit. If the ACC wire does not have voltage, repair the open in the wire between the passenger's under-dash fuse/relay box and the display unit.■
  1. Turn the ignition switch OFF.
  1. Disconnect the display unit 20P connector.

  1. Check for continuity between display unit 20P connector terminal No. 10 and body ground.
Is there continuity?
YES -
Go to Step 6 .
NO -
Repair the open in the wire between the display unit and body ground (G503).■
  1. Disconnect the navigation unit connector B (12P).

  1. Check for continuity between body ground and display unit 20P connector terminal No. 5 and No. 15 individually.
Is there continuity?
YES -
There is a short to body ground in the circuit between the display unit and the navigation unit. Replace the affected shielded harness.■
NO -
Go to Step 8 .

  1. Check for continuity between display unit 20P connector terminal No. 5 and navigation unit connector A (20P) terminal No. 10.
Is there continuity?
YES -
Go to Step 9 .
NO -
There is an open in the circuit between the display unit and the navigation unit. Check for poor connections or loose terminals at the display and navigation units. If a poor connection or loose terminal is found, replace the affected shielded harness.■

  1. Check for continuity between display unit 20P connector terminal No. 15 and navigation unit connector A (20P) terminal No. 20.
Is there continuity?
YES -
NO -
There is an open in the circuit between the display unit and the navigation unit. Check for poor connections or loose terminals at the display and navigation units. If a poor connection or loose terminal is found, replace the affected shielded harness.■