Control Unit Input Test

WARNING: This page is about a different car, the 2006 Acura MDX, 2005 Acura MDX, 2004 Acura MDX, and 2003 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: If only the gauge lights do not work, check the gauge circuit and unit first ('04-'06 models).

Before testing the dash lights brightness control functions, troubleshoot the multiplex control system (see TROUBLESHOOTING ).
Driver's Multiplex Control Unit
Remove the driver's multiplex control unit from the driver's under-dash fuse/relay box.
Inspect the connector and socket terminals to be sure they are all making good contact.
- If the terminals are bent, loose or corroded, repair them as necessary, and recheck the system.
- If the terminals look OK, go to step 4.
  
  Fig 1: Identifying Driver's Under-Dash Fuse/Relay Box Socket
  Courtesy of AMERICAN HONDA MOTOR CO., INC.
  
  Fig 2: Identifying Driver's Multiplex Control Unit Connector B
  Courtesy of AMERICAN HONDA MOTOR CO., INC.
  
  Fig 3: Identifying Driver's Under-Dash Fuse/Relay Box Connector J
  Courtesy of AMERICAN HONDA MOTOR CO., INC.
  
  Fig 4: Identifying Driver's Under-Dash Fuse/Relay Box Connector M
  Courtesy of AMERICAN HONDA MOTOR CO., INC.

With the driver's multiplex control unit still disconnected, make these input tests at the connector and driver's under-dash fuse/relay box socket.

If any test indicates a problem, find and correct the cause, then recheck the system.

If all the input tests prove OK, go to step 5.

TEST CONDITION TEST DESIRED RESULT CHART

Cavity	Wire	Test condition	Test: Desired result	Possible cause if result is not obtained
A12	Fuse/relay box socket	Under all conditions	Check for voltage to ground: There should be battery voltage.	Blown No. 13 (7.5 A) fuse in the passenger's under-dash fuse/ relay box Faulty driver's under-dash fuse/ relay box An open in the wire
A14	Fuse/relay box socket	Under all conditions	Check for continuity to ground: There should be continuity.	Poor ground (G401) Faulty driver's under-dash fuse/relay box An open in the wire
B3 B4	ORN/WHT and WHT/RED	Adjusting dial rotated	Check for resistance between the B3 and B4 terminals: There should be 0-20 k ohm as the dial is rotated.	Faulty dash lights brightness controller An open in the wire

Reconnect the driver's multiplex control unit to the driver's under-dash fuse/relay box, and perform the following input tests at the appropriate connectors on the driver's under-dash fuse/relay box.
- If any test indicates a problem, find and correct the cause, then recheck the system.
- If all the input tests prove OK, the driver's multiplex control unit must be faulty; replace it.
  
  Fig 5: Test Condition Test Desired Result Chart
  Courtesy of AMERICAN HONDA MOTOR CO., INC.