Multiplex Control Unit Input Test

1.Remove the dashboard under cover.

2.Disconnect the under-dash fuse/relay box connectors C, E, F, J, K, O, P, Q, X and Y.
NOTE: All connectors are wire side of female terminals.

 

3.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 4.

4.Reconnect the connectors to the under-dash fuse/relay box, and make sure these input tests at the appropriate connectors on the 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 multiplex control unit must be faulty, replace the under-dash fuse/relay box assembly.

Cavity Wire Test condition Test: Desired result Possible cause if result is not obtained 
J4 BLK Under all conditions Check for voltage to ground:
There should be less than 1 V. 
  • Poor ground (G301)
  • An open in the wire
 
Y6 BLK Under all conditions Check for voltage to ground:
There should be less than 1 V. 
  • Poor ground (G502)
  • An open in the wire
 
J2 WHT/RED Under all conditions Check for voltage to ground:
There should be battery voltage. 
  • Blown No. 9 (10A) fuse in the under-hood fuse/relay box
  • An open in the wire
 
Q3 GRN Driver's door open Check for voltage to ground:
There should be 1 V or less. 
  • Faulty driver's door switch
  • An open in the wire
 
Driver's door closed Check for voltage to ground:
There should be 5 V or more. 
  • Faulty driver's door switch
  • Short to ground
 
Q4 LT GRN/RED Passenger's door open Check for voltage to ground:
There should be 1 V or less. 
  • Faulty passenger's door switch
  • An open in the wire
 
Passenger's door closed Check for voltage to ground:
There should be 5 V or more. 
  • Faulty passenger's door switch
  • Short to ground
 
Q8
·
C8
·
F1 
GRN/ORN
·
GRN/RED 
Parking brake lever pulled Check for voltage to ground:
There should be 1 V or less. 
  • Faulty parking brake switch
  • An open in the wire
 
Parking brake lever released Check for voltage to ground:
There should be 5 V or more. 
  • Faulty parking brake switch
  • Short to ground
 
Q5 BLU/RED Ignition switch ON (II) Driver's seat belt is unbuckled. Check for voltage to ground:
There should be 1 V or less. 
  • Faulty driver's seat belt switch
  • Poor ground (G551)
  • An open in the wire
 
Ignition switch ON (II) Driver's seat belt is buckled. Check for voltage to ground:
There should be 5 V or more. 
  • Faulty driver's seat belt switch
  • Short to ground
 
P18 RED Tailgate open Check for voltage to ground:
There should be 1 V or less. 
  • Faulty tailgate switch
  • An open in the wire
 
Tailgate closed Check for voltage to ground:
There should be 5 V or more. 
  • Faulty tailgate switch
  • Short to ground
 
X5 RED/WHT Ignition key is in the ignition switch Check for voltage to ground:
There should be 1 V or less. 
  • Faulty ignition key switch
  • Poor ground (G401)
  • An open in the wire
 
Ignition key is out of the ignition switch Check for voltage to ground:
There should be 5 V or more. 
  • Faulty ignition key switch
  • Short to ground
 
F9 BLU/WHT Under all conditions Check for voltage to ground:
There should be 5 V or more. 
  • An open or short in the wire
 
C3 WHT Under all conditions Check for continuity to ground:
There should be continuity. 
  • An open or short in the wire
 

Cavity Wire Test condition Test: Desired result Possible cause if result is not obtained 
X8 WHT/BLK Under all conditions Attach to ground: The ignition key light should come on. 
  • Blown No. 3 (15A) fuse in the under-hood fuse/relay box
  • Blown LED
  • An open in the wire
 
O7 GRN/RED Ceiling light switch in the middle position, all doors closed Attach to ground: The ceiling light, spotlights should come on. 
  • Blown No. 3 (15A) fuse in the under-hood fuse/relay box
  • Faulty ceiling light or spotlights
  • An open in the wire
 
C11 BLU Under all conditions Attach to ground: Dash lights should come on. 
  • Blown No. 2 (15A) fuse in the under-hood fuse/relay box
  • Faulty taillight relay
  • An open in the wire
 
F8 GRN/RED Disconnect the brake fluid level switch 2P connector, and jump the GRN/RED and BLK Check for voltage to ground:
There should be less than 1 V. 
  • Faulty brake fluid level switch
  • An open in the wire
 
Brake fluid level switch connector disconnected, jumper wire removed Check for voltage to ground:
There should be 5 V or more. 
  • Faulty brake fluid level switch
  • Short to ground
 
E10 YEL All doors, tailgate and hatch glass closed, ignition key removed Check for voltage to ground:
There should be battery voltage in the sleep mode and 3-7 volts when awake. 
  • An open or short in the wire
 
K10 GRY/RED All doors, tailgate and hatch glass closed, ignition key removed Check for voltage to ground:
There should be battery voltage in the sleep mode and 3-7 volts when awake. 
  • An open or short in the wire
 
Y1 BRN/YEL Under all conditions Check for continuity between the Y1 terminal and the No. 13 terminal of the ABS modulator-control unit.
There should be continuity. 
  • An open in the wire
 
Q2 GRN/WHT Hatch glass open Check for voltage to ground:
There should be 1 V or less. 
  • Poor ground (G601, G701)
  • Faulty hatch glass latch switch
  • An open in the wire
 
Hatch glass closed Check for voltage to ground:
There should be 5 V or more. 
  • Faulty hatch glass latch switch
  • Short to ground