2010 Cadillac Truck Escalade/ESV RWD V8-6.2L Page 1782
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptor
DTC P0128
- Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module
(ECM) supplies 5 V to the ECT sensor signal circuit and supplies a ground to the low reference circuit.
The purpose of this diagnostic is to analyze the performance of the thermostat by using the ECT sensor to determine if the engine coolant will
increase at the correct rate, and also to meet the calibrated target temperatures under various operating conditions.
The ECM uses the start-up ECT and the start-up intake air temperature (IAT) to begin the diagnostic calculation. The air flow into the engine is
accumulated, and vehicle speed, distance, and engine run time are also factored in to determine if the ECT does increase normally and reach the
calibrated target temperatures.
Conditions for Running the DTC
* DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0171, P0172, P0174, P0175, P0502, P0503 are
not set.
* The start-up IAT is warmer than -7掳C (+19掳F).
* The start-up ECT is colder than 70掳C (158掳F), when the IAT is above 10掳C (50掳F).
OR
* The start-up ECT is colder than 50掳C (122掳F), when the IAT is below 10掳C (50掳F).
* The engine run time is between 90 s and 22 min.
* The vehicle has traveled greater than 2.4 kilometers (1.5 miles) at greater than 8 km/h (5 mph).
* The accumulated airflow is between 20-75 g/s, with the minimum average airflow greater than 10 g/s.
* The fuel ethanol percentage is less than 85 %.
* This DTC runs once per ignition cycle when the above conditions are met.
Conditions for Setting the DTC
The ECM detects that the minimum ECT of 75掳C (167掳F) has not been met, when the IAT is greater than 10掳C (50掳F).
OR
The ECM detects that the minimum ECT of 55掳C (131掳F) has not been met, when the IAT is less than 10掳C (50掳F).
Action Taken When the DTC Sets
DTC P0128 is a Type B DTC.
Conditions for Clearing the MIL/DTC
DTC P0128 is a Type B DTC.
