Detroit Diesel MBE 4000 DDEC VI Troubleshooting Manual page 551

75.2 SPN 729/FMI 4
This diagnosis is typically a short to ground.
75.2.1 Short to Ground Check
Check as follows:
1. Disconnect the Grid Heater connector.
2. Disconnect the 120–pin MCM connector.
3. Measure the resistance between pins 3 and 4 of the Grid Heater connector.
[a] If the resistance is less than 5 Ω, repair the short between pins 3 and 4 of the
Grid Heater connector and pins 92 and 95 of the 120–pin MCM connector.
Refer to section 75.2.1.1.
[b] If the resistance is greater than 5 Ω, go to step 4.
4. Measure the resistance between pin 3 of the Grid Heater connector and ground.
[a] If the resistance is less than 5 Ω, repair the short between pin 3 of the Grid Heater
connector and ground. Refer to section 75.2.1.1.
[b] If the resistance is greater than 5 Ω, replace the Grid Heater.
75.2.1.1 Verify Repairs
Perform the following steps to verify repairs.
1. Turn the ignition OFF. Reconnect all connectors.
2. Turn ignition ON. Clear codes with diagnostic tool.
3. Start and run the engine for one minute. Stop the engine.
4. Check diagnostic tool for codes.
[a] If no codes are displayed, troubleshooting is complete.
[b] If code 729/4 is not logged, and other codes are logged, troubleshoot the logged codes.
[c] If code 729/4 and other codes are logged, review this section to find the error. If no
error is found, call the Detroit Diesel Customer Support Center (313–592–5800).
All information subject to change without notice.
6SE568 Copyright © PRELIMINARY 2007 DETROIT DIESEL CORPORATION
(Rev. )
MBE 4000 DDEC VI TROUBLESHOOTING GUIDE
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