Important Information

Subject: DTC P0128 Or Engine Will Not Reach Operating Temperature - keywords 4.8 5.3 6.0 cooling coolant heat HVAC LR4 LM7 L59 LQ4 MIL P0128 SES temp #PIP3267B - (11/19/2007)

Models:

1999-2007 Chevrolet Silverado Classic

1999-2006 Chevrolet Suburban, Tahoe

1999-2007 GMC Sierra Classic

1999-2006 GMC Yukon

Classic Body Style Vehicles

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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Possible DTC P0128 or the engine will not reach operating temperature after a radiator replacement. Some replacement radiators may be missing a restriction orifice that is built into the right side radiator tank. The restriction orifice is molded into the nipple that feeds the radiator surge tank.

The engine may not reach operating temperature, or set DTC P0128 due to excessive coolant flow to the radiator surge tank.

Recommendation/Instructions:

If SI diagnostics have been completed for DTC P0128 and no problem was found, contact the customer to discuss radiator replacements, and check the vehicle history for previous radiator replacements. If the radiator was replaced for a cooling system concern, or replaced during a front end body shop repair, it may be missing the radiator surge tank restriction orifice. Remove the surge tank hose from the radiator and visually inspect the radiator tank nipple that feeds the surge tank. If the radiator is missing the surge tank restriction orifice there will be an increased amount of coolant flow to the surge tank. Excessive coolant flow may induce DTC P0128.

If the radiator surge tank restriction is missing, the radiator needs to be replaced with the proper replacement radiator as listed in the GMSPO parts catalog.