Ford Mustang Cabin Air
Mark Houlahan
Tech Editor, Mustang Monthly
November 22, 2013

A Breath of Fresh Air

I have a 2006 Mustang and am replacing the cabin air filter on the firewall under the hood. What kind of holder is the filter supposed to fit into other than a hole in the firewall?

Lincolnton, NC

The cabin air filter first showed up on the S197 Mustang redesign for 2005. Since then, the Mustang has had one in the right side cowl area, accessed from under the hood. Simply remove a couple of plastic clips and pull the right side vent up to gain access to the filter. The filter media actually sits in a black plastic “tray” that snaps into a plastic receiving ring on the firewall. To remove/install the filter, you have to line up the two tabs at the bottom of the filter and then push the top in until it snaps into place. If your filter is missing the tray (as if someone threw the whole assembly away by accident), you’ll have to order a replacement filter tray from your Ford dealer.

Dancing Service Engine Light

In June 2011, I became the lucky owner of a 2011 Mustang GT convertible with the new 5.0L Coyote engine. It was first registered in December 2010 with 4,000 km on the odometer. In the mid 1980s, I owned a 5.0L Mustang for five years without any major problems. Therefore, I thought that even though nobody imports the Mustang to Denmark, I would not experience any trouble that the nice people at the nearby Ford shop could not fix.

Being a Danish retiree at 67 years old, I spend the winter in Spain and some months during the summer in Denmark. In September 2011, we drove the 3,000 km to Spain. I must say I love the car, especially after driving it in the Spanish mountains. In February 2012, the service engine light came on in the instrument cluster. I looked in the owner’s manual and changed to another gasoline station, using 98 octane. After a week and 600 km, the service engine light was still on. Unable to find a nearby shop for Mustangs, I drove to a skilled Dutch mechanic who was used to American cars. His computer could tell us something, but not exactly what was wrong, so he checked the car further and found no failures. I left the workshop after the service engine light was switched off.

After 350 km, it came on again and stayed there until I drove to another shop, which did not find anything wrong, but once again switched the light off. After a week the warning light came on once again, so I tried an authorized Ford shop. They also did not have the right diagnostic equipment. They could see something from the onboard computer, but not exactly what was wrong. Yet another shop, called Mustang Deutschland, got the computer results from the first shop I visited. Their conclusion—don’t drive the 3,000 km to Denmark in the car because it may damage the engine!

Otherwise, my Mustang had been a dream to drive. I went once again to the Dutch mechanic. He turned off the service engine light and I started the long drive back to Denmark. What a miracle! No service engine light came on during the whole summer back in Denmark. Do I dare take a longer drive in the Mustang again? No mechanic can find anything wrong. The car sounds perfect, even after 20,000 km. The exhaust measures correctly and there are no exhaust leaks.

Gunner Thygesen

That’s quite the drive for summer vacation! For those geographically challenged, Gunnar is driving from Denmark through Germany and France to get to Spain! That’s 1,800 miles each way or roughly going from New York City to San Antonio, Texas!

It’s often tough to diagnose such issues via an email or letter, and it’s even more cumbersome with extreme distance and language barriers, but we’ll still try to help. In this case, I believe one issue is your ’11 Mustang GT is an early built car with a December 2010 first registration. These early ’11 Mustangs had some teething problems with PCM calibrations and even the oxygen sensors triggering the service engine light due to a diagnostic trouble code (DTC). Unfortunately, while the fix is relatively simple for a Ford dealer in the U.S. to flash the latest calibration into your PCM and/or replace one or both of the oxygen sensors, it is a little more difficult in Denmark. We really don’t think these issues, while sensitive enough to trigger your warning light, will do any damage to your engine. If a strong visual inspection has been performed and there are no damaged wires, hoses, leaks, etc. then we’d not get too worried about the issue. That being said, we would recommend going to Ford of Europe’s Denmark website at and selecting the “service” link and see if you can find a shop willing to work with you to get the latest Mustang PCM flash for your car. Best of luck!

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