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2005 GMC Envoy 4.2 L Failed emissions due to DTC P0128 (coolant thermostat- coolant temp below thermostat regulating temperature). Do I just replace the thermostat?

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Yes, Have a repair shop replace it, it comes with a new housing.

Posted on Feb 01, 2011

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Posted on Jan 02, 2017

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2005 montana sv6 sitting in traffic temp gauge goes up codes P0128 and P0481 present


DTC P0128 Engine Coolant Temperature (ECT) Below Thermostat Regulations Temperature
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.

P0481
Cooling Fan Relay 2 Control Circuit
PCM
DTC P0480 or P0481

Have you changed the thermostat ?
Do you know how to test cooling fan relay (S)
Battery positive voltage is supplied to the cooling fan 1 relay from the COOL FAN #1 fuse. The powertrain control module (PCM) controls the cooling fan 1 relay by grounding the low speed cooling fan relay control circuit via an internal solid state device called a driver.
Battery positive voltage is supplied to the cooling fan 2 relay and the cooling fan 3 relay from the COOL FAN #2 fuse. The PCM controls the relays by grounding the high speed cooling fan relay control circuit.
When the PCM is commanding a relay on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a relay, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.
The PCM will monitor the control circuit for the following conditions:
• A short to ground
• A short to voltage
• An open circuit
• An open relay coil
• An internally shorted or excessively low resistance relay coil
When the PCM detects any of the above conditions, the DTC will set and the affected driver will be disabled.

Jul 01, 2017 | Cars & Trucks

1 Answer

CODE #PO128 KEEPS RETURNING AND AC CUTTING IN & OUT


It's a thermostat/coolant issue. The definition is here:


P0128 Engine Coolant Temperature Below Thermostat Regulating Temperature



Possible Causes
  • Check the operation of the thermostat (it may be stuck open)
  • Coolant level is too low, or the coolant mixture is incorrect
  • ECT sensor connector is damaged (check pins for damage, and for moisture)
  • ECT sensor signal circuit has a high resistance condition
  • ECT sensor has failed

Jan 20, 2011 | 2003 GMC Envoy

1 Answer

2005 Mercury Monterey with check engine code P0128; what does it mean?


P0128 is Coolant Thermostat ( Coolant Temp Below Thermostat Regulating Temperature ). The thermostat may be stuck open, preventing normal operating Temperature from beeing reached.How is the heat inside the car is it below normal ? Or the engine Coolant Temperature Sensor may be faulty and needs to be replaced. Good Luck and have a good XMASS.

Dec 17, 2010 | 2005 Mercury Monterey

1 Answer

Sensor keep coming in for code PO128 - insofficient ambient temp was does this mean how can i fix it


DTC P0128: Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature
Do you have any issues with heat in the vehicle? If so the thermostat may need replaced If not the engine coolant temperature sensor is most likely reading incorrectly due to a bad sensor or connection to the sensor.

Dec 01, 2010 | 2008 Chevrolet Cobalt

1 Answer

Code PO128 came up on my 2005 Explorer. Any ideas on how to correct the problem?


P0128 - Coolant Thermostat (coolant Temp Below Thermostat Regulating Temperature). First check the coolant level,if its low then refill the coolant.If the coolant is checked full then get the thermostat replaced.-----------That's it.

Nov 18, 2010 | Ford Explorer Cars & Trucks

2 Answers

P0128 coolant temp below thermostat/regulating temp


P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

Symptoms: You will likely not notice any drivability problems other than the MIL illumination.

Causes: A code P0128 may mean that one or more of the following has happened:
* Low engine coolant level
* Leaking or stuck open thermostat
* Faulty cooling fan (running too much)
* Faulty coolant temperature (ECT) sensor
* Faulty intake air temperature (IAT) sensor

Possible Solutions: Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
* Verify coolant strength & level
* Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
* Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
* Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
* If the above items check out good, replace the thermostat
* If Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 code

Hope helps (remember to rate and comment this).

Sep 27, 2010 | 2006 Dodge Caravan

1 Answer

Dtcdescriptionp0128andrepair


DTC P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

What does that mean?
This means that the engine's PCM detected that the engine has not reached the required temperature level within a specified amount of time after starting the engine. The intent of the P0128 code is to indicate a faulty thermostat. Similar codes: P0125

In determining the engine did not reach a "normal" temperature, it takes into account the length of time the vehicle has been running, the intake air temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensor reading, and the speed of the vehicle.

Symptoms:
You will likely not notice any drivability problems other than the MIL illumination.

Causes:
A code P0128 may mean that one or more of the following has happened:
* Low engine coolant level
* Leaking or stuck open thermostat
* Faulty cooling fan (running too much)
* Faulty coolant temperature (ECT) sensor
* Faulty intake air temperature (IAT) sensor

Possible Solutions:
Past experience indicates that the most likely solution is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-II code:
* Verify coolant strength & level
* Verify proper cooling fan operation (check if it's running more than it should). Replace if necessary.
* Verify proper engine coolant temperature (ECT) sensor operation, replace if necessary.
* Verify proper intake air temperature (IAT) sensor operation, replace if necessary.
* If the above items check out good, replace the thermostat
* If Nissan vehicle, check for a TSB such as this one. The ECM may need to be reprogrammed to correct the P0128 code


Hope helps (remember rated this).

Jul 01, 2010 | 2004 GMC Envoy

1 Answer

I have a 2000 hyundai accent and it has a fault code of P0128 what does that mean


P0128=Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature),
time to replace thermostat,coolant not at correct temp

Dec 09, 2009 | 2000 Hyundai Accent

2 Answers

Check engine light on, diagnostic code 0128 and 0410 keep coming up


P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

P0410 - Secondary Air Injection System Malfunction
(has to do with exhaust system)

Note: There is a technical service bulletin (TSB) regarding code P0410 for a number of GM models. The TSB calls for the replacement of the AIR pump and the installation of a new secondary injection hose.

Oct 13, 2009 | 2005 Chevrolet TrailBlazer

1 Answer

Engine code P0128


check your temperature sending unit and be sure it is working properly and then check to see that your thermostat is working properly if you are getting heat inside of the vehicle from the heater then this would be a good indication that your thermostat is working properly. also check your coolant level is correct.
code P0128 is coolant thermostat ( coolant temp below thermostat regulating temperature )

Oct 14, 2008 | 2005 Jeep Grand Cherokee

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