We recently bought a 2017 mustang. It has 30,000 miles on it.

It drives great. No issues with it's performance. When it sits in the sun a bit, and gets really hot, the wrench light will pop up on the dash. This happens when you start up the car, before it's been driven.

After you drive it around a bit, and it's cooled down from the sun, the light will go off (typically after you turn the car off, and back on again). It never pops up when it's been in the shade, or it's not sitting in the sun getting hot.

No codes. We checked with our OBD scanner, and the auto shop. No codes pop up.

I'm assuming it's some sort of sensor that's getting hot while sitting in the sun, but I have no idea where to start looking.

Any ideas?

Couple other notes:
-Throttle body is clean
-No transmission issues that we can tell, it shifts/drives very smooth.
-Battery/starter both tested fine.

Did you Scan for codes when the light is on.? Did you use forscan? There are several modules and on my fords they dont all show up on standard scanners. Also, some code for mine only scan up when the light is on.

What kind of mustang?

The GT350's and GT's in 2016 (and I think 2017) have poor cooling issues. To drive a GT350, a track car, on the track you have to add a differential cooler, an oil cooler, and a transmission cooler. Ford really screwed the pooch there

Gen 1 "voodoo" engines also have high oil consumption rate and you'll need to add oil every 1,000 miles

These are not relevant if you don't have a gt350. If it's a 2.3 turbo, you might just have a vacuum leak: make sure the hoses intakes etc are on tight.

Scanned ourselves, at AutoZone and at the dealer. Nothing has shown up. (scanned when the light was on and off).

It's a 6 cylinder (my son wishes it was a GT)

active grille shutter issue?

Not familiar with that, so I'm going to say no.


It really only pops up when it sits in the hot sun for a while.

If the light is on there's a code somewhere. The code is what triggers the light.

…unless the heat is exposing a flaw in the circuit board in the dash, but that'd be unique to yours and nearly impossible to find.

Forscan is what I use to pull and reset codes.

Yeah, you'd think. But no code pops up no matter who scans it.

The light only comes on when it's been sitting in the heat for a while, and goes away fairly quickly. My best guess is some sort of sensor gets too hot, or electrical issue like you mentioned.


Guess we'll just roll with it for now.

AgGrad99 said:

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Not familiar with that, so I'm going to say no.

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Solid logic

Probably some emissions related sensor. Maybe evap.

There should be 3 sections of DTCs in the scan.

• current DTCs
  
• persistent DTCs
  
• DTC history
  

You want the history before the tool clears it. It should have the code and a count.

Agreed. But it's showing nothing.

Stat Monitor Repairman said:

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Probably some emissions related sensor. Maybe evap.

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I considered that, but it's odd that it would be there on start up, and go away once it runs a minute.

akaggie05 said:

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AgGrad99 said:

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Not familiar with that, so I'm going to say no.

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Solid logic

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I have the same car, but it's the 2.3T Ecoboost. Those engines are famous for "ecobooming" themselves at low mileage due to evap purge valve or fuel pressure sensor issues. When/if the mileage gets higher, they have head gasket issues. Somehow, mine is at 115k and going strong. I have change the purge valve and the pressure sensor (twice). No other serious issues. I've heard the old school v6 is by far the most reliable of the 3 options. For some reason I thought it was only available in rental spec.

I guess not. I've seen them around, and this one was a single-owner, weekend car, for an older guy. But to be honest I dont know much about the model.

The GTs are stout.
The Power Pack really opens it up. 1st gear is almost useless with the 3.73 rear gearing.

Yeah they are. Good friend of mine has one and it's a blast to drive.

What engine are we talking about?

3.7L V6

Does it have any kind of forward collision warning system? Could be the cameras getting too hot to operate correctly and then start working when they cool down.

Auto or manual? If auto, one guy with similar problems had his diagnosed as torque converter. You might check that out. No codes there, either.

Stat Monitor Repairman said:

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Probably some emissions related sensor. Maybe evap.

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That's a stretch.

OBD (and 2) emphasize emissions related codes.

Care to elaborate on your position given no code seem to be revleaed in a system for whch OBD+ was created.

91AggieLawyer said:

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Auto or manual? If auto, one guy with similar problems had his diagnosed as torque converter. You might check that out. No codes there, either.

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Auto.

This weekend I had it in the shade outside. Light never popped up. But on Thursday it did, after being parked outside for a while.

After being in the sun, you can start the car, light is on. Then, while still parked, let it run for 60 seconds. Turn the car off, and then back on again...and the light is gone. Super weird.

I'm going to take it straight to the dealership to run codes again, next time the light is still on. Just want to make sure 100% we ran it when the light was on.

JamesPShelley said:

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Stat Monitor Repairman said:

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Probably some emissions related sensor. Maybe evap.

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That's a stretch.

OBD (and 2) emphasize emissions related codes.

Care to elaborate on your position given no code seem to be revleaed in a system for whch OBD+ was created.

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Op said it happens when it sits in the sun. Shows the CEL right on startup but no code.

Vapor expanding from the heat might put something out of parameter in the emissions system on startup but it's not showing a code for whatever reason.

I just remembered from previously when we had a Ford. The wrench light is not the same as a CEL. Can't remember all the nuances but believe they are two different things. Wrench is more transmission / drivetrain related IIRC.

Does it do it during the cooler months? I asked earlier if it has any kind of forward collision warning system or adaptive cruise control, because my wife's 2017 Odyssey will sometime's show a "FCW Failure" after it's been sitting out in the blazing sun during the summer (especially when we have a window shade up) that will go off once the van has cooled down and the camera has cooled back into operating temp.

That may be what you're seeing if it's not giving any codes.

We've only had it a month...so I'm not sure. But it didnt pop up until it got really hot recently.

It doesnt have a forward crash warning system I dont think, but I'm guessing it's something similar.

akaggie05 said:

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I just remembered from previously when we had a Ford. The wrench light is not the same as a CEL. Can't remember all the nuances but believe they are two different things. Wrench is more transmission / drivetrain related IIRC.

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You're correct. There is a check engine, and then the wrench. Im finding out the wrench is a 'catch-all' for ford (at least this model). It could be anything from the gas cap not on tight, to a bad transmission.