ISSUE: The check engine came on in my 2008 F250 6.4 two days ago. I purchased the truck last summer. It had 70,000 miles and now has 81,000. I pulled the codes and it was P0128 two times. Doing some research here and on youtube, I learned that the codes are engine coolant related and point to either the T-stat being stuck open or a faulty sensor.


QUESTION: Given that I purchased an extended warranty (Powertrain only), is this something I should delve into, or just send it to the dealer?


Thanks

 

The T-stats on these engines have been updated. Is that the only code flagged, or did you get a P00B7 to go along with it, along with a "reduced engine power" message display? If not, you likely need to have your PCM reflashed with the updated calibration which de-rates engine power output more aggressively when it detects any parameters that the PCM "doesn't like". Replace your upper and lower rad hoses too with the updated 2 o-ring design as well when you do your T-stats.

 

Only the code P0128. But it appears twice. Thanks for the information. I kinda think the T-stat is sticking because it takes a long time to warm up. I bought it during the summer, so I guess I didn't notice that. Now that it's winter (or what we call winter in CA), I notice it. Not only in the temp indicator needle, but in the cab with the heater on.


Also, in reference to the other thread about the new Ford owner who got fluids changed and began suffering numerous problems, I did the same thing when I purchased this truck. I have not suffered any of those problems, but I don't know what kinds of fluids they put in. Guess I'll have to look into that.


Thanks

 

Did you look at your coolant degas bottle at all? Maybe you are low on coolant too.


These motors require you to constantly check your fluids.

 

Here is what I have on the factory Ford service manual for trouble shooting this code. See if anything here points you in the right direction.

Jeff

<table border="1" cellpadding="3" cellspacing="0"><caption>P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) </caption> <tbody> <tr> <th align="center" valign="bottom">
</th> <th align="center" valign="bottom">
</th> <th align="center" valign="bottom">
</th> <th align="center" valign="bottom">
</th> <th align="center" valign="bottom">
</th></tr> <tr> <td style="BORDER-RIGHT: medium none" align="left" valign="top">Description: </td> <td style="BORDER-LEFT: medium none" colspan="4" align="left" valign="top">Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine. </td></tr> <tr> <td style="BORDER-RIGHT: medium none" align="left" valign="top">Possible Causes: </td> <td style="BORDER-LEFT: medium none" colspan="4" align="left" valign="top">

• Insufficient warm up time
• Low engine coolant level
• Leaking or stuck-open thermostat
• Inoperative engine coolant temperature (ECT) sensor

</td></tr> <tr> <td style="BORDER-RIGHT: medium none" align="left" valign="top">Diagnostic Aids: </td> <td style="BORDER-LEFT: medium none" colspan="4" align="left" valign="top">Refer to Section 1, Powertrain Control Software for system information. </td></tr> <tr> <td style="BORDER-RIGHT: medium none" align="left" valign="top">Application </td> <td style="BORDER-LEFT: medium none" align="left" valign="top">
</td> <td align="center" valign="top">Key On Engine Off </td> <td align="center" valign="top">Key On Engine Running </td> <td align="center" valign="top">Continuous Memory </td></tr> <tr> <td style="BORDER-RIGHT: medium none" align="left" valign="top">All </td> <td style="BORDER-LEFT: medium none" align="left" valign="top">
</td> <td colspan="3" align="center" valign="top">GO to Pinpoint Test K . </td></tr></tbody></table>


This pinpoint test is intended to diagnose the following:

• ECT sensor (12A648)
• harness circuits: ECT and SIGRTN
• powertrain control module (PCM) (12A650)

<table border="1" cellpadding="3" cellspacing="0"> <caption>TEMPERATURE VS. RESISTANCE VALUES (APPROXIMATE) </caption> <tbody> <tr> <th align="center" valign="bottom">°C </th> <th align="center" valign="bottom">°F </th> <th align="center" valign="bottom">Ohms </th></tr> <tr> <td align="center" valign="top">100 </td> <td align="center" valign="top">212 </td> <td align="center" valign="top">2,080 </td></tr> <tr> <td align="center" valign="top">90 </td> <td align="center" valign="top">194 </td> <td align="center" valign="top">2,803 </td></tr> <tr> <td align="center" valign="top">80 </td> <td align="center" valign="top">176 </td> <td align="center" valign="top">3,836 </td></tr> <tr> <td align="center" valign="top">70 </td> <td align="center" valign="top">158 </td> <td align="center" valign="top">5,337 </td></tr> <tr> <td align="center" valign="top">60 </td> <td align="center" valign="top">140 </td> <td align="center" valign="top">7,556 </td></tr> <tr> <td align="center" valign="top">50 </td> <td align="center" valign="top">122 </td> <td align="center" valign="top">10,908 </td></tr> <tr> <td align="center" valign="top">45 </td> <td align="center" valign="top">113 </td> <td align="center" valign="top">13,216 </td></tr> <tr> <td align="center" valign="top">40 </td> <td align="center" valign="top">104 </td> <td align="center" valign="top">16,092 </td></tr> <tr> <td align="center" valign="top">35 </td> <td align="center" valign="top">95 </td> <td align="center" valign="top">19,696 </td></tr> <tr> <td align="center" valign="top">30 </td> <td align="center" valign="top">86 </td> <td align="center" valign="top">24,329 </td></tr> <tr> <td align="center" valign="top">25 </td> <td align="center" valign="top">77 </td> <td align="center" valign="top">30,000 </td></tr> <tr> <td align="center" valign="top">20 </td> <td align="center" valign="top">68 </td> <td align="center" valign="top">37,352 </td></tr> <tr> <td align="center" valign="top">15 </td> <td align="center" valign="top">59 </td> <td align="center" valign="top">46,797 </td></tr> <tr> <td align="center" valign="top">10 </td> <td align="center" valign="top">50 </td> <td align="center" valign="top">59,016 </td></tr> <tr> <td align="center" valign="top">5 </td> <td align="center" valign="top">41 </td> <td align="center" valign="top">74,940 </td></tr> <tr> <td align="center" valign="top">0 </td> <td align="center" valign="top">32 </td> <td align="center" valign="top">95,851 </td></tr> <tr> <td align="center" valign="top">-5 </td> <td align="center" valign="top">23 </td> <td align="center" valign="top">123,485 </td></tr> <tr> <td align="center" valign="top">-10 </td> <td align="center" valign="top">14 </td> <td align="center" valign="top">160,313 </td></tr> <tr> <td align="center" valign="top">-15 </td> <td align="center" valign="top">5 </td> <td align="center" valign="top">209,816 </td></tr> <tr> <td align="center" valign="top">-20 </td> <td align="center" valign="top">-4 </td> <td align="center" valign="top">276,959 </td></tr> <tr> <td align="center" valign="top">-30 </td> <td align="center" valign="top">-22 </td> <td align="center" valign="top">496,051 </td></tr> <tr> <td align="center" valign="top">-40 </td> <td align="center" valign="top">-40 </td> <td align="center" valign="top">925,021 </td></tr></tbody></table>
Engine Coolant Temperature (ECT) Sensor Connector






<table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">Pin </th> <th align="center" valign="bottom">Circuit </th></tr> <tr> <td align="left" valign="top">1 </td> <td align="left" valign="top">SIGRTN (Signal Return) </td></tr> <tr> <td align="left" valign="top">2 </td> <td align="left" valign="top">ECT (Engine Coolant Temperature) </td></tr></tbody></table>
Powertrain Control Module-E (PCM-E) Connector






<table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">Pin </th> <th align="center" valign="bottom">Circuit </th></tr> <tr> <td align="left" valign="top">55 </td> <td align="left" valign="top">SIGRTN (Signal Return) </td></tr> <tr> <td align="left" valign="top">67 </td> <td align="left" valign="top">ECT (Engine Coolant Temperature) </td></tr></tbody></table>


K1 PRELIMINARY DIAGNOSIS FOR DIAGNOSTIC TROUBLE CODES (DTCS) P0117, P0118 AND P0128

• Carry out a visual inspection.
• Retrieve and record all DTCs.
• Record the freeze frame data.
• Clear all the DTCs.
• Carry out the on-demand self-test.

Are DTCs P0117, P0118, or P0128 present?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">For DTC P0117, GO to K2 .

For DTC P0118, GO to K4 .

For DTC P0128, GO to K8 . </td> <td width="50%">Unable to duplicate the condition. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the concern. REPAIR as necessary. REFER to Section 3 GO to Pinpoint Test QT . </td></tr></tbody></table> K2 DTC P0117

• [*]
• [*]
• [*]
• [*]

Is DTC P0118 present?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">INSTALL a new ECT sensor.

CLEAR the DTCs. REPEAT the self-test. </td> <td width="50%">GO to K3 . </td></tr></tbody></table> K3 CHECK THE ECT SIGNAL CIRCUIT FOR A SHORT TO GROUND

• Key in OFF position.
• PCM-E connector disconnected.
• Measure the resistance between:
  
  <table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">( + ) ECT Sensor Connector, Harness Side </th> <th align="center" valign="bottom">( - ) </th></tr> <tr> <td align="left" valign="top">ECT - Pin 2 </td> <td align="left" valign="top">Ground </td></tr></tbody></table>

Is the resistance greater than 10,000 ohms?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">GO to K10 . </td> <td width="50%">REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test. </td></tr></tbody></table> K4 DTC P0118

• Simulate the opposite DTC.
• Key in OFF position.
• Connect a 5 amp fused jumper wire between the following:
  
  <table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">Point A ECT Sensor Connector, Harness Side </th> <th align="center" valign="bottom">Point B ECT Sensor Connector, Harness Side </th></tr> <tr> <td align="left" valign="top">ECT - Pin 2 </td> <td align="left" valign="top">SIGRTN - Pin 1 </td></tr></tbody></table>
• Key ON, engine OFF.
• Carry out the KOEO on-demand self-test.

Is DTC P0117 present?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">INSTALL a new ECT sensor.

CLEAR the DTCs. REPEAT the self-test. </td> <td width="50%">GO to K5 . </td></tr></tbody></table> K5 CHECK THE ECT SIGNAL CIRCUIT FOR AN OPEN

• Key in OFF position.
• PCM-E connector disconnected.
• Measure the resistance between:
  
  <table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">( + ) PCM-E Connector, Harness Side </th> <th align="center" valign="bottom">( - ) ECT Sensor Connector, Harness Side </th></tr> <tr> <td align="left" valign="top">ECT - Pin 67 </td> <td align="left" valign="top">ECT - Pin 2 </td></tr></tbody></table>

Is the resistance less then 5 ohms?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">GO to K6 . </td> <td width="50%">REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test. </td></tr></tbody></table> K6 CHECK THE ECT SIGNAL RETURN CIRCUIT FOR AN OPEN

• Measure the resistance between:
  
  <table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">( + ) PCM-E Connector, Harness Side </th> <th align="center" valign="bottom">( - ) ECT Sensor Connector, Harness Side </th></tr> <tr> <td align="left" valign="top">SIGRTN - Pin 55 </td> <td align="left" valign="top">SIGRTN - Pin 1 </td></tr></tbody></table>

Is the resistance less then 5 ohms?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">GO to K7 . </td> <td width="50%">REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test. </td></tr></tbody></table> K7 CHECK THE ECT SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

• Key ON, engine OFF.
• Measure the voltage between:
  
  <table border="1" cellpadding="3" cellspacing="0"> <tbody> <tr> <th align="center" valign="bottom">( + ) ECT Sensor Connector, Harness Side </th> <th align="center" valign="bottom">( - ) </th></tr> <tr> <td align="left" valign="top">ECT - Pin 2 </td> <td align="left" valign="top">Ground </td></tr></tbody></table>

Is any voltage indicated?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">REPAIR the short circuit. CLEAR the DTCs. REPEAT the self-test. </td> <td width="50%">GO to K10 . </td></tr></tbody></table> K8 DTC P0128: CHECK THE ENGINE COOLANT LEVEL

• [*]

Is the engine coolant fill level correct?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">GO to K9 . </td> <td width="50%">REFER to the Workshop Manual Section 303-03, Engine Cooling for cooling system diagnosis.

REPAIR as necessary.

CLEAR the DTCs.

REPEAT the self-test. </td></tr></tbody></table> K9 CHECK THE SENSOR OPERATION

• Run the engine until the engine temperature stabilizes.
• Verify the radiator hoses are hot and the cooling system is pressurized.
• Access the PCM and monitor the ECT PID.

Is the temperature greater than 77°C (170.6°F) ?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">The test is complete.

DISREGARD the current diagnostic trouble code (DTC) at this time. DIAGNOSE the next DTC. GO to Section 4, Diagnostic Trouble Code (DTC) Charts and Descriptions . </td> <td width="50%">REFER to the Workshop Manual Section 303-03, Engine Cooling for cooling system diagnosis.

REPAIR as necessary.

REPEAT the self-test. </td></tr></tbody></table> K10 CHECK FOR CORRECT PCM OPERATION

• Disconnect all the PCM connectors.
• Visually inspect for:
  • pushed out pins
  • corrosion
• Connect all the PCM connectors and make sure they seat correctly.
• Carry out the PCM self-test and verify the concern is still present.

Is the concern still present?
<table border="1" cellpadding="3" cellspacing="0" width="92%"> <tbody> <tr> <th width="50%">Yes </th> <th width="50%">No </th></tr> <tr> <td width="50%">INSTALL a new PCM. REFER to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM) . </td> <td width="50%">The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. </td></tr></tbody></table>

 

i would be looking into replacing the Stats if the coolant level is ok. i would look into your extended warranty to see if it will pay for that and how much of a deductible you would have. quick look i would say to pay someone to do it you would be $300+