Cooling System - MIL ON/DTC P0128 Set
Bulletin No.: 06-06-04-004Date: January 18, 2006
TECHNICAL
Subject:
L66 Engine Repeat and/or Intermittent Malfunction Indicator Lamp (MIL) Illuminated with Diagnostic Trouble Code (DTC) P0128 (Engine Coolant Temperature (ECT) is Below Thermostat Regulating Temperature) Set (Replace Engine Coolant Thermostat Assembly and Return Original Thermostat to Warranty Parts Center (WPC))
Models:
2004-2006 Saturn VUE
with 3.5L V6 Engine (VIN 4 - RPO L66)
Condition
Some customers may comment on intermittent and/or repeat "Service Engine Soon" (U.S.) or "Check Engine Soon" (Canada) malfunction indicator lamp (MIL) being illuminated. Upon investigation, the technician may find DTC P0128 (Engine Coolant Temperature (ECT) is Below Thermostat Regulating Temperature) set.
^ General Motors Warranty identified that vehicles initially repaired by replacing the Engine Coolant Temperature Sensor (ECT), of the vehicles repaired, 50 percent returned with the same DTC set.
^ General Motors Warranty also identified that vehicles initially repaired by replacing the Engine Coolant Thermostat Assembly had no customer return reported, with the same DTC set.
Cause
The return of the Engine Coolant Thermostat Assembly to the Warranty Parts Center (WPC) and root cause analysis indicates that the engine thermostat assembly is stuck fully open and is inoperable in the vehicle, causing DTC P0128 to set.
Correction
Important:
Do NOT replace the Engine Coolant Temperature Sensor (ECT) for a DTC P0128.
A faulty thermostat that stays open slightly and/or sticks fully open can cause DTC P0128 to set in cold weather when the vehicle is started and allowed to sit while warming up. If the published diagnostics in SI lead to the replacement of the Engine Coolant Thermostat Assembly, install Engine Coolant Thermostat Assembly P/N 12581519. Refer to Thermostat Replacement in the Engine Cooling sub-section of SI. Return the original thermostat for additional analysis to the WPC. The thermostat will be returned to the WPC following the normal WPC parts return process as outlined in Corporate Bulletin Numbers 05-00-89-042 and 05-00-89-080. DO NOT SHIP ANY PARTS TO THE WPC WITHOUT AN OFFICIAL WPC REQUEST.
Warranty Parts Center (WPC)
45 Northpointe Drive
Orion, MI 48359
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
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