My wifes 2.4SS is running rough at Idle, A/c will not come on & the Fan is running constant from the radiator. Any help would be great! I have it setup to go to the dealer tomorrow but would like to aviod it if Possible! Thanks

[ECM] P0128 - Coolant Thermostat (SES) (Old) (History) (Current) (Immature)
[ECM] P0128 - Coolant Thermostat


Continuous Tests
Misfire: Complete
Fuel System: Complete
Comprehensive Component: Complete


Once Per Trip Tests
Catalyst: Complete
Heated Catalyst: n/a
Evaporative System: Complete
Secondary Air System: n/a
A/C System Refrigerant: n/a
Oxygen Sensor: Complete
Oxygen Sensor Heater: Complete
EGR System: n/a

 

I had that code pop up when I changed my thermostat to a lower temperature model. Once I swapped back in the stock one the code went away. I had exactly the same symptoms too. This was on a 2002 Firebird but it was the same code and all. I'm just saying it's probably just the stat. They run like $10-15 I believe.

 

Could be your Thermostate.Temp sensor,Bad connection at temp sensor or worst case your Pcm.


DTC P0128
Circuit Description
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 vehicle has been driven within the 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.

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

Disconnect the ECT sensor.
Inspect for the following conditions:
• Engine coolant leaking through the ECT sensor

• Corrosion on the ECT sensor terminals

• Improper or corroded terminals at the ECT harness connector

• Loose terminals in the ECT harness connector

• Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Test and verify the proper operation and the heat range of the thermostat.

 

TY guys I had it in this morning & they replaced the sensor!