How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask Brian Your Own Question

Brian
Brian, Auto Service Technician
Category: Ford
Satisfied Customers: 1227
Experience:  5 years Ford Technical Hotline/Service Engineer. 2005 Ford Master Cert. Automotive Technology degree
367936
Type Your Ford Question Here...
Brian is online now
A new question is answered every 9 seconds

po117 Engine Coolant Temp Circuit Low Input

Resolved Question:

got a 97 f150 4.2 code read po117 temp gauge maxed out. Changed both sensors still didnt fix it. Looked for shorts, still didnt find any, thought the short was the gauge. I changed the instrument cluster and the gauge worked fine, the light went off. Then I drove the truck later on and the same code came back on but the gauge works fine.
Submitted: 6 years ago.
Category: Ford
Expert:  Brian replied 6 years ago.
There are 2 separate coolant temperature sensors. 1 is the sender for the gauge cluster. The other is for the engine computer. The computer only sets codes for the sensor with the Gray/Red stripe, and Light Green/Red stripe wires. There is one sensor right on top of the thermostat housing (where the upper radiator hose connects to engine). The other sensor is nearby, on the driver's side of the thermostat housing.

If the computer is not seeing at least 250 F from the Engine Coolant Temperature sensor during the self test, the code will set. If the check engine light is not on, this code may just be a result of not satisfying all the self-test criteria. The engine must be idling at full normal temperature before running the self test codes. If a bad thermostat is keeping the temps down, this code could result.

graphic


The above wiring diagram shows the sensor circuit that can cause the code. The wires must be checked to ensure that the sensor receives reference voltage and that the signal voltage is present at the computer pin 38.

Circuit 359 is reference voltage of 5 volts, supplied by pin 91 of the PCM (computer). This voltage is shared by many sensors. The voltage drops created by the ECT sensor is read by the PCM monitoring voltageat pin 38 circuit 354. If the voltage is less than .2 volts during the self test, the code sets because low voltage is equivalent to low temperature. The hotter the sensor gets, the closer the voltage gets to 5 volts supplied as reference. So, you need to make sure that the test is carried out properly, and that the voltage at pin 38 does indeed vary with temperature. If you have a scan tool that can monitor the data from the engine sensors, use it to look at ECT sensor voltage signal. If the voltage is stuck low, this means that circuit 354 is shorted to ground, and needs to be repaired.
Brian, Auto Service Technician
Category: Ford
Satisfied Customers: 1227
Experience: 5 years Ford Technical Hotline/Service Engineer. 2005 Ford Master Cert. Automotive Technology degree
Brian and 11 other Ford Specialists are ready to help you

JustAnswer in the News:

 
 
 
Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.
 
 
 

What Customers are Saying:

 
 
 
  • AlvinC answered a question about my Ford truck that only someone with an in-depth knowledge of his subject would have known what was going on. Rich D USA
< Last | Next >
  • AlvinC answered a question about my Ford truck that only someone with an in-depth knowledge of his subject would have known what was going on. Rich D USA
  • Because of your expertise, you armed me with enough ammunition to win the battle with the dealer. They are installing a fuel filter and fuel pump at no charge to me. Molly USA
  • I needed help with my car on Saturday morning....got a response in 5 minutes, and it was the perfect solution. Thanks again to your service. Jason V. Kirkland, WA
  • I do know, after going though this with JustAnswer, that I can somewhat trust my mechanic but I will always contact you prior to going there. BR New Jersey
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P Elm City, NC
  • used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future. David L. Richmond, TX
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil Marysville, CA
 
 
 

Meet The Experts:

 
 
 
  • Ron

    ASE Certified Technician

    Satisfied Customers:

    20942
    23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
< Last | Next >
  • http://ww2.justanswer.com/uploads/FO/fordguy4u/2011-12-17_222940_HPIM1257.64x64.JPG Ron's Avatar

    Ron

    ASE Certified Technician

    Satisfied Customers:

    20942
    23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
  • http://ww2.justanswer.com/uploads/MU/muddyford/2012-6-13_1204_1.64x64.png Chris (aka- Moose)'s Avatar

    Chris (aka- Moose)

    Ford Technician

    Satisfied Customers:

    22382
    16 years experience with Ford.
  • http://ww2.justanswer.com/uploads/JM/jmcdo28/2012-2-23_01655_resized.64x64.jpg John Mc's Avatar

    John Mc

    Ford Technician

    Satisfied Customers:

    5493
    19 years Ford Lincoln Mercury experience
  • http://ww2.justanswer.com/uploads/wmarti7/2009-4-18_04332_Avatar.jpg Chuck's Avatar

    Chuck

    ASE Certified Technician

    Satisfied Customers:

    1684
    33 Years Experience,Ford Senior Master,ASE Master,L1 Advanced Engine Performance
  • http://ww2.justanswer.com/uploads/CR/crzydrvr00/2013-11-3_12123_246347.64x64.jpg Richard's Avatar

    Richard

    ASE Certified Technician

    Satisfied Customers:

    1518
    12 years at a Ford Lincoln/Mercury and Jaguar dealer as a technician and shop foreman.
  • http://ww2.justanswer.com/uploads/BA/baddad1/2014-4-1_23659_avatar.64x64.jpg Mike V.'s Avatar

    Mike V.

    Auto Service Technician

    Satisfied Customers:

    789
    25 years experience on all makes and models, Licensed NYS Inspector.
  • http://ww2.justanswer.com/uploads/lostrider/2009-9-26_23144_php4VNWAA_c1PM1.jpg lostrider's Avatar

    lostrider

    Ford Technician

    Satisfied Customers:

    2940
    ASE Master Technician, Ford Senior Master Technician,Diesel certified, ASE Master, 22 yrs FORD exp.
 
 
 
Chat Now With A Ford Mechanic
Brian
Brian
976 Satisfied Customers
5 years Ford Technical Hotline/Service Engineer. 2005 Ford Master Cert. Automotive Technology degree