Checking The 15-Supply To The Control Module

Fig 1: Identifying Ignition ON

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Fig 2: Disconnecting Control Unit

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• The breakout box connected
• Control module disconnected.
• Ignition on.

  Check the 15-supply by measuring the voltage between terminal #4 (#A4) and ground terminals #16 (#A16) and #46 (#A46). The voltmeter should read battery voltage.

  Check that the fuse for the circuit is intact if the voltage is incorrect.

  If the fuse is blown, check the cable between brake control module terminal #4 (#A4) and the fuse. Check for a short-circuit to ground.

  If the fuse is intact, check the cable between brake control module terminal #4 (#A4) and the fuse. Check for an open-circuit.

  If no fault is found in the cable between brake control module terminal #4 (#A4) and the fuse, check the cable between the fuse and the ignition switch.

  Other information 

  • To connect the breakout box, see CONNECTING THE BREAKOUT BOX, BRAKE CONTROL MODULE (BCM) 
  Fig 3: Breakout Box

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  Fig 4: Identifying Voltage Display

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Was a fault detected? 

• YES 

  OKAY:  Troubleshooting has been completed.

• NO 

  see CHECKING THE 30-SUPPLY (VALVES) TO THE CONTROL MODULE