Bulletin No.: PIP5846
Published date: 03/25/2022

Preliminary Information
PIP5846 Diagnostic Tip for Duramax Diesel Hydro locked Engine.
Models
Brand:

VIN:

Model
Years:

Model:

from

to

Engine: Transmissions:

Chevrolet Silverado 2500HD/3500HD

2022

NF233624 N1211255 6.6 L5P All

GMC

Sierra 2500HD/3500HD

2022

NF233624 N1211255 6.6 L5P All

Chevrolet

Silverado 4500HD, 5500HD and
6500HD

2022

NH378231 NH497303

6.6
L5D

All

Involved Region or Country North America
Customers may have a concern of:
1. The engine does not crank.
2. The F8UD starter fuse may be open.
3. The engine is hydro-locked.
4. There may be coolant in the engine oil.
Condition

5. The oil level may be over lled.
6. The Malfunction Indicator Light (MIL) may be illuminated.
7. The "Low Coolant" light may be on.
8. There may be excessive pressure in the cooling system.
9. There may be discolored coolant in the coolant surge tank.
10. There may be coolant in the exhaust system causing an exhaust aftertreatment
related Diagnostic Trouble Code (DTC).

Cause

This condition may be caused by coolant entering one or more cylinders causing a
hydro-lock.

Inspect the engine for a hydro-locked condition.
Here are some good indicators:
1. Complaint of a hard crank at rst and then resumes normal crank speed.
2. The F8UD starter fuse is open (L5P) or the starter or starter cables may be overheated (L5D).
3. NOx sensor 1 may be wet with coolant.
NOTE: "Tar" looking soot or humidity that does not smell like coolant does not qualify.
4. The engine oil may be over lled and coolant in the engine oil.
5. "Washed" looking glow plug tips.
6. The may be coolant in a combustion chamber.
If you nd any three of the above indicators the engine is likely hyrdo-locked.

Version History
Version
Modi ed

1
03/24/2022 - Created on

© 2022 General Motors. All Rights Reserved.