An engine coolant temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the powertrain control module (PCM) for engine control and as an enabling criteria for some diagnostics.


The air flow coming into the engine is accumulated and used to determine if the engine has been driven within conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally, or does not reach the regulating temperature of the thermostat, the diagnostics that use ECT as enabling criteria may not run when expected.


This DTC will only run once per ignition cycle within the enabling condition. If the PCM detects the calibrated amount of air flow and engine run time have been met, and the ECT has not met the minimum thermostat regulating temperature, DTC P0128 sets.


The most common cause for this is just a faulty thermostat. Or, low coolant level.


More Auto Repair Help

Leave your comments

Post comment as a guest

0 / 300 Character restriction
Your text should be in between 10-300 characters
    • No comments found

    How Things Work

    Brakes- Rear Drum- How Do They Work

    The drum brake system consists of the following:

    Drum Brake Shoes: Applies mechanical output force, from hydraulic brake wheel cylinders, to friction surface of brake drums.

    Brake Drums: Uses mechanical output force applied to friction surface from drum brake shoes to slow speed of tire and wheel assembly rotation.

    Read more...

    Common Engine Codes

    Cam Crank Correlation Code P0014 P0016

    P0016 - P0014. The engine control module (ECM) uses the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor pulses to monitor the correlation between the crankshaft and camshaft position.

    Read more...

    Latest Articles

    1999 GMC Savanna Brake Pedal ...

    1999 GMC Savanna 3500. Engine Size : 5.7 Question Here: Master cylinder leaks from reservoir replaced 3 times plus lids no sign of any other leaks. ...

    Ford Explorer Transmission ...

    I was an idiot to think it was bad luck to have taken a loan for my 2002 Ford Explorer XLT in 2008, only to have a $3,200 transmission problem before ...

    Buick Century Cleaned Battery ...

    Question: I have a Buick 1996 Century it was having problems starting so i checked the battery terminal to clean it and it arched so did i blow the ...