MBE 4000 DDEC VI Troubleshooting – Section 5.1 CPC Wiring Harness

Section 5.1
CPC Wiring Harness

To determine if the CPC wire harness is causing starting difficulty, perform the following steps:‪

1. Turn the ignition switch to the ON position.
2. Connect to DDDL 7.x
3. Determine if CPC data is being received by the DDDL 7.x. If no data is being received, check for intermittent code or a fault and no codes by doing the following:
   1. Check for poor mating of the connector halves or terminals not fully seated in the connector body (backed-out terminals).
   2. Look for improperly formed or damaged terminals. All connector terminals in the problem circuit should be carefully inspected to determine proper contact tension. Use a mating terminal to test the contact tension.
   3. Electrical system interference may be caused by a defective relay, or a switch causing an electrical surge. Look for problems with the charging system (alternator, etc.). In certain cases, the problem can be made to occur when the faulty component is operated as in the case of a relay.
   4. Verify alternator grounds are clean and making good contact. Disconnect the alternator belt to test.
   5. Wiggle wires and harnesses to try to make the problem active or to occur again.
4. If data is being received by the DDDL 7.x, check the vehicle circuit breakers or fuses; refer to "5.1.1 Vehicle Circuit Breakers or Fuses Check" .

Section 5.1.1
Vehicle Circuit Breakers or Fuses Check

To determine if the vehicle circuit breakers are causing starting difficulty, visually check CPC circuit breakers or fuses to determine if circuit breaker(s) or fuse(s) are tripped or blown.‪

1. If circuit breakers are tripped, determine cause and repair or replace as necessary; refer to OEM guidelines.
2. If circuit breakers are not tripped, measure the voltage at the MCM power harness. Contact Detroit Diesel Customer Support Center at 313-592-5800 in the interim.