temp sensor Transit Connect Temp Sensor Failure

[kruss77]

About a week ago my 2015 TC started struggling to start.  It would crank a few seconds before actually starting.  It seemed that each day it got a little worse.  I also noticed that my fuel economy took a dump during that time as well.  Additionally, when it would crank prior to starting I noticed the strong smell of unburned fuel in the garage.  That's never a good sign.  Yesterday, it cranked for about 15 seconds (a long time for any fuel injected vehicle to crank and not fire up) before it finally started.

 

Once started, it didn't immediately respond to throttle input and it seemed to be searching for the correct engine RPM.  After a minute it settled down and appeared ok to drive (throttle response returned).  It was then that I drove it directly to my local repair shop who theorized that it was the engine temp sensor.

 

Upon completion of their diagnostics, they found that my engine temp sensor was reading 117 degrees below zero.  The implication is that it was telling the computer to dump more fuel into the engine to compensate for the extremely cold temperatures it was sensing.  Obviously, the sensor was bad because it was clearly NOT 117 below zero outside.  As such, one hour and $143.00 later it was fixed.  (I felt $143.00 is a bit high for a repair of this type, but I needed to get back on the road ASAP and wasn't gonna squabble over the $50.00 I felt I should have saved!)

 

It may be worth noting that the temp sensor is mounted in the head and doesn’t measure coolant temperature, but simply the temperature of the cylinder head itself.  This is unusual in my experience, and explains why the dash temp gauge was already in the 'normal' range at only a quarter mile from my house each day (coolant simply doesn't heat up that fast -but cylinder heads do).

 

Additionally, I suspect the throttle response got better when I started it earlier because -as the cylinder head heated up (the sensor is mounted in the cylinder head right between plug 2 & 3) the sensor started reading the combustion heat in the head and allowed more throttle input once the motor warmed up.

 

It runs like normal now, and my otherwise great fuel economy has returned. 

 

The Ford part number for this temp sensor is: 8S4Z-6G004-A and can be found at most ANY ford dealership.  They run about $53.00USD.
 

I hope that some find this information helpful.

 

Ken

 

[windguy]

@kruss77 - Thanks for sharing. Great write-up and pics too. Smart that you drove it to a repair shop without delaying.

Personally, I think the repair cost was a bargain. $53 parts and $90 labor, which you said took about an hour. That's about right.

But also the tech quickly diagnosed the problem and fixed it correctly with no collateral damage, and you got back on the road in an hour.  I put a lot of value in that.

 

PS - Welcome to the forum. How about a few pics of your van? (if you haven't done so yet)

[jrm223]

Just wait until the "ambient air temperature sensor" goes out, lol. Mine went at something like 33K miles, I believe. I have a 2015, also, but it's at 114K miles now. The whole front bumper needs to be removed to get at that sensor, but at least mine was under warranty when it failed. Many FoMoCo vehicles have the same sensor and other forums report the same issue with the AAT. This is the first I've ever heard about the cylinder head temp sensor, though. 

[kruss77]

 

 

 

 

On 12/17/2019 at 11:59 AM, windguy said:

@kruss77 - Personally, I think the repair cost was a bargain. $53 parts and $90 labor, which you said took about an hour. That's about right.

But also the tech quickly diagnosed the problem and fixed it correctly with no collateral damage, and you got back on the road in an hour.  I put a lot of value in that.

 

Yes, you're right.  It truly was a great deal!  And they always take really good care of me there (and often very quickly)!  Plus, I'm so used to diagnosing and effecting my own repairs that I guess deep down I feel I could have done it for the cost of the sensor.  Perhaps I just needed something to complain about!!!! 

 

Ken

[kruss77]

 

 

 

 

On 12/17/2019 at 11:59 AM, windguy said:

PS - How about a few pics of your van? (if you haven't done so yet)

 

My van is a simple white TC cargo van used for shuttling parts around, so nothing to look at!

 

Ken

[Fifty150]

On 12/18/2019 at 1:50 PM, jrm223 said:

Mine went at something like 33K miles, I believe. 

 

 

As I recall, I got a check engine light indicating the sensor fault when the van was a few months old.  I cleared the diagnostic trouble code, and the MIL never activated for that again. 

[jrm223]

On 12/21/2019 at 4:02 PM, Fifty150 said:

 

 

As I recall, I got a check engine light indicating the sensor fault when the van was a few months old.  I cleared the diagnostic trouble code, and the MIL never activated for that again. 

 

Not likely on an AAT, must have been a different sensor, who knows. Mine just randomly started giving me wrong temperatures, but never a CEL for it. The dash would say it was like -20*F, then gradually go up in random increments, like -2*F/8*F/20*F and eventually made it's way back to 93*F or whatever the actual temp was at the time. So it was just random temperatures and it wasn't quite consistent at first, but after it happened a couple days in a row towards the end of that week, I brought it into Ford for repair. When the AAT reports below a certain temperature, the A/C compressor will not kick-on at all to prevent freezing the lines or compressor - not a big deal for me, since I don't use A/C, but that's another thing for people to know about with it. And, like the cylinder head temp sensor, the AAT is used for air-fuel ratio, so mine would have been using some extra fuel until it figured out the real air temperature was almost 120*F warmer than the AAT originally said - although not nearly as much fuel as kruss77 van at -177*F.