Open Fuses Set Glow Plug DTCs

The Check Engine MIL and several glow plug-related DTCs may be set on some 2024 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD models equipped with the 6.6L Duramax diesel engine (RPO L5P). DTCs that may be set in the Engine Control Module (ECM) may include:

  • P066A (Cylinder 1 Glow Plug Control Circuit Low)
  • P066C (Cylinder 2 Glow Plug Control Circuit Low)
  • P066E (Cylinder 3 Glow Plug Control Circuit Low)
  • P067A (Cylinder 4 Glow Plug Control Circuit Low)
  • P067C (Cylinder 5 Glow Plug Control Circuit Low)
  • P067E (Cylinder 6 Glow Plug Control Circuit Low)
  • P068C (Cylinder 7 Glow Plug Control Circuit Low)
  • P068E (Cylinder 8 Glow Plug Control Circuit Low)

An open fuse F5 (F5BA) will result in cylinders 1, 4, 6 and 7 all setting DTCs P066A, P067A, P067E and P068C simultaneously. And an open fuse F6 (F6BA) will result in cylinders 2, 3, 5 and 8 all setting DTCs P066C, P066E, P067C and P068E simultaneously.

In addition, terminal damage in the X950D 55-way connector may result in Glow Plug Control Circuit DTC P0671, P0672, P0673, P0674, P0675, P0676, P0677 or P0678 setting.

Before replacing or disturbing any glow plugs, check the Battery Distribution Unit (BDU) Fuse Assembly for any blown fuses. (Fig. 15) Be sure to check for 12V on the BDU ring terminal while wiggling the cable. Some blown fuse conditions will intermittently make contact.

If a fuse is intermittent or open, replace the BDU assembly. Be sure to torque all fasteners to specification. Do not over torque. The 10 mm nut should be torqued to 6 Nm; 13 mm nuts should be torqued to 15 Nm.

 

Fig. 15

 

Also check for any bent terminals in the X950D 55-way connector. (Fig. 16) The X950D connector can be separated by disengaging the red CPA and squeezing the corners of the connector.

 

Fig. 16

 

For more information, refer to #PIP5911.

– Thanks to Steven Ulch

 

 

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