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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ, LMM & LML engine specific topics.

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Old 10-11-2004, 06:42 PM
scape scape is offline
Join Date: Mar 2002
Location: Jefferson City, MO
Posts: 7

Hey guys. It has been a long time since I have been on the board.

My 01 has 65,000 trouble free miles, but I have SES light on. I took it to the dealer today and they said it was the P0380 Glow Plug Feedback Circuit

It goes in the shop tomorrow, but I was hoping one of you would be wise enough to give me a clue on what this code meant. I would like to know before I hear what the dealer says.

Old 10-12-2004, 04:34 AM
cabletech cabletech is offline
Join Date: Apr 2004
Location: Monument, CO
Posts: 140

maybe this will help.

DTC P0380 California RPO YF5, NE1
Circuit Description

The glow plug system is used to assist in providing the heat required to begin combustion during cold engine temperatures. The glow plugs are heated before and during cranking, as well as initial engine operation. The engine control module (ECM) controls the glow plug ON times by monitoring coolant temperature and glow plug voltage. The California Glow Plug system has eight individual glow plug supply circuits between the controller and the glow plugs. If the feedback voltage from the controller to the ECM is not within range, DTC P0380 will set.
Conditions for Running the DTC

The ignition is ON.
Conditions for Setting the DTC
The glow plugs are commanded OFF and the glow plug feedback is more than 2 volts. or
The glow plugs are commanded on and the glow plug feedback is not between 5 volts and 6.2 volts.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids


If the glow plug relay is stuck in the ON position, check for proper operation of the glow plugs. When the glow plugs are commanded ON by the scan tool, an internal engine control module (ECM) timer protects the glow plugs from damage by cycling them ON for 3 seconds and the OFF for 12 seconds. The glow plug relay battery feed wire nut at the relay should be tested for proper torque. The California glow plug system will send the following voltages, or signals to the ECM:

Signal Voltage

Glow Plugs Failed Open









Less than 1.3

4 or more
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Old 10-29-2004, 04:28 PM
Brandenburg Brandenburg is offline
Join Date: Mar 2002
Location: Vermontville Michigan
Posts: 69

scape, do you know what the dealer did to fix it?
2001 Red D/A 4x4 Standard Cab Autometer Ultra-Lite Boost/EGT, KD4&lt;5, RJ, HI/ODL, 285x75BFGATs<br /> <a href=\"\" target=\"_blank\"></a>
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