DD15 Troubleshooting – Section 74.1 SPN 729/FMI 0

Section 74.1
SPN 729/FMI 0

This fault condition is typically Grid Heater permanently on.‪

Check as follows:‪

1. Disconnect the Grid Heater harness connector.
2. Disconnect the MCM 120–pin connector.
3. Measure the resistance between pin 1 of the Grid Heater harness connector and ground
   1. If the resistance is less than 5 Ω, repair short to ground between pin 1 of the Grid Heater harness connector and pin 79 of the MCM 120–pin connector. Refer to "74.1.1 Verify Repairs" .
   2. If the resistance is greater than 5 Ω, replace the Grid Heater. Refer to "74.1.1 Verify Repairs" .

Section 74.1.1
Verify Repairs

Verify repairs as follows:‪

1. Turn ignition OFF.
2. Reconnect any electrical connections that were disconnected to perform the diagnosis.
3. Clear codes with DDDL 7.0 or latest version.

   ENGINE EXHAUST ‪
   To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area. Engine exhaust is toxic.‪

4. Start and bring engine up to operating temperature (over 140°F/60°C).
5. Verify operation is satisfactory and no warning lamps illuminate. If warning lamps illuminate, troubleshoot the codes. If assistance is required, call the Detroit Diesel Customer Support Center at 313–592–5800.