Question about 2002 Pontiac Montana

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2002 elantra p0128 code. Cleared with a scanner but keeps coming back on. Coolant level seems ok. Fans turn on/off automatically. Coolant temp gage sometimes stays below C when driving on freeway at night, but on streets or idle it goes to about 1/2 between C and H and barely moves. At startup heating inside the car is felt in 2-3mins. Upper and lower radiator hoses are hot. Please help me diagnose the real problem and avoid being ripped by the repair shop.

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If you have not fixed the fault even when you remove the code the fauld is still their.
Leaking or stuck open thermostat

  • Low engine coolant level
  • Insufficient warm up time
  • Faulty engine coolant temperature sensor
  • Engine coolant temperature sensor harness is open or shorted
  • Engine coolant temperature sensor circuit poor electrical connection
  • look over all .I would look more at coolant levels

    Posted on Jun 16, 2017

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    • Pontiac Master
    • 807 Answers

    I would start with the cheapest fix first. Change the air filter and then replace the coolant temp sensor. Then perform another ODBII scan. Let the scan be your guide to any repairs to avoid buying parts you don't need.

    Posted on Jun 16, 2017


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    Posted on Jan 02, 2017

    • 53 Answers

    SOURCE: running hot

    replace the therostat ( most likely )

    and the radiator cap

    Posted on Nov 30, 2008

    james klgr
    • 362 Answers

    SOURCE: 2002 montana getting overheated

    sounds like a stuck thermostat. but check if the system has a bleeder screw if it does burp it and that will help also.

    Posted on Dec 13, 2008

    • 142 Answers

    SOURCE: 97 transport 3.4 engine- New radiator,

    Are your cooling fans working? that will definately be a problem if not working. if they are working shut car off and feel the radiator is it the same temp all over or is it hot in only top or one smaller area. if you do not have same temp feeling on all of radiator your radiator may be plugged.

    Posted on Oct 09, 2009

    SOURCE: where do I locate the collant temp senor that

    Hi standing in front of the car looking at the engine it's on the top right side of the engine,next to the top radiator hose inlet.

    3.4L Engine

    NOTE Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

    1. Drain the coolant below the level of the Engine Coolant Temperature (ECT) sensor.
    2. Disconnect the sensor electrical connector.
    3. Carefully remove the ECT sensor.

      0996b43f80205354.jpg enlarge_icon.gifenlarge_tooltip.gif Fig. Removal and installation of the coolant temperature sensor

    To install:

    NOTE Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

    NOTE Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

    1. Coat the threads with sealer P/N 9985253 or equivalent.
      NOTE Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
    2. Install the ECT sensor and tighten the sensor to 15 lb-ft (20 Nm).
    3. Connect the ECT sensor electrical connector.
    4. Refill the cooling system

    Hope this helps,Thank You for using fixya..iluv2fish....Ray....

    Posted on Jul 10, 2010

    • 613 Answers

    SOURCE: Temp Gage while on local

    sounds like the thermostat is staying closed or maybe a leak in one of the hoses id check it and if no loss of fluid and the antfreeze is topped off then id replace the thermostat see if fixes it make sure get the thermostat gasket too like 6 bucks for both

    Posted on Sep 24, 2010

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    you say that you have replaced the thermostat and it is just under 210 F which is 99 c or almost boiling point
    you will have to investigate why it is running so hot.
    check that you put the thermostat in correctly ( bulb section to block/head water
    Next point --the codes are originated by the coolant temperature sensor ( puts the fans on and sets the ECM fuel/air ratio for the engine ) so to get it off you will need to reset with a scan tool

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    Primary cooling fan only comes on when i turn ac on

    You would need a scanner and an inferred temp sensor to troubleshoot the system.
    You need to know what the actual engine temp is, and what the temp sensor is telling the computer.
    If and when the engine reaches 220 degrees, the engine temp sensor should be sending that data to the computer and it should ground the fan relay to activate it.
    Unplugging the sensor and having the fan run tells you the sensor is connected, and there should have been a trouble code set at that time.
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    Apr 16, 2013 | 2002 Chevrolet Malibu

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    I have a 2007 Chevy Expreess 1500 van. When ambient temperature drops below say 80f outside I get a P0128 check eng code. If during the day the ambient temp raises above 8-85f the light will go out...

    P0128 is a generic code to indicate that the engine isn't reaching proper temp. If it has
    the Vortec 4.3 like my S-10 is (I am having a similar problem). Check the overflow
    tank as the tube will come off and allow air into the system, also check the radiator
    coolant level under the cap. The third item is the intake manifold gasket, check for
    seepage. If all these things are good I would replace the thermostat (my S-10 had one
    sticking which could actually be seen on the temp gage, it wasn't reaching the normal
    195 degrees). If you have the temp gage on your dash watch for low temperature to
    indicate a bad thermostat, luckily it sounds as if yours is sticking open as mine did.
    Hope this helps.

    Mar 26, 2011 | Chevrolet 1500 Cars & Trucks

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    I have a 2004 Chevy Impala. As I was driving home yesterday I had the heater on full blast - temp outside appx. 60. The check engine light came on and I had a P0128 code. Could this be due to keeping...

    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.

    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

    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


    I hope this helps a bit!

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