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The Tone, the Battery, and the MAF

Not even one full day since I replaced the air filter and cleaned the MAF sensor did the errors come back. The first time I enthusiastically punched the throttle, the “PSM Off” and “ABS” lights illuminated. Seems to me, it’s likely the MAF, so I ordered one online for $175.

Two days later, I was driving on the highway and the CEL (Check Engine Light) illuminated. If I have a bad MAF, then the CEL should be on, so this didn’t worry me too much. However, it there was some additional strange behavior. A day or two after that, I punched the throttle to escape the vicinity of an obnoxiously slow driver – I don’t know why people think that going 30 in a 45 is acceptable. When I did this, the “PSM Off” and “ABS” lights illuminated (as expected), but within a few second the CEL went off. That was weird.


Seemingly unrelated, I started experiencing a high-pitched tone, like one of those used to test your hearing. You can barely hear it, but it’s there, and it drives you insane. This was coming from the stereo system, which was only recently installed. It was such an annoying tone that I have to keep the radio powered off, or else I would go mad.

I stopped by Audio Design (since they did all the stereo work) and spoke with Mike, the owner of the place. Mike is an incredibly knowledgeable person when it comes to anything stereo related… and Porsche related. His top priority is quality workmanship. I can’t boast enough about the attention to detail and the high quality work his shop performs.

Mike seemed a bit surprised there was a tone, he actually checked for that before releasing the car to me after all the work was complete. And, it certainly wasn’t there the first couple of weeks. But somehow, it’s there now. He explained how factory stereos generally put out less volts than after market stereos and that it may need to be grounded. I’m probably butchering his explanation, but it made perfect sense when he explained it. However, not to let any possibility—no matter how remote—pass by unnoticed, he mentioned there was always a chance it could be the battery or the alternator.

It dawned on me that I had no idea how old the battery in the car might be. The following morning I got in my car and it was a bit slow to startup. Not terribly slow, but slower than normal. This reminded me of the time my Boxster was having trouble starting, it had the same behavior, and it needed a new battery. So, I took the 996 to RMG and had Dan check my battery. As turns out, the battery was seven years old and tested poorly. I had the battery replaced on the spot. After replacing the battery, Dan tested the entire electrical system and the new battery, which specifically tests the alternator. Everything passed with flying colors.

However, that did not resolve the high-pitched tone coming from my stereo system. But, it’s possible there may be another cause. When Dan went to replace the battery, he noticed the horn honked when the factory alarm was set. Apparently, it’s not supposed to do this. He immediately asked if I had the stereo replaced (Dan didn’t know about the history of my stereo).

I told Dan the whole story, how there was terrible after market crap in there and that I had it all removed and had a Porsche head unit put in. He told me the horn honking is a sign the stereo has been removed. There’s a connector on the left side of the sleeve that senses if the radio is there or not. If not, one of the faults is the horn honks when you set the alarm.

Dan ran a full diagnostics and found a few errors that pointed to the MAF, which I told him I had already ordered, but he dove deeper in and found that indeed the radio error code was there, noting it was missing. He popped off the left side of the console switch plate and revealed a brown and blue cable.

This cable is the alarm sensor and should be plugged into the left side of the sleeve. Now, since I have the Porsche Classic Radio Navigation system, chances are it doesn’t have that connector as it was designed for cars that don’t have this in the first place. If that’s the case, the cable should be taped off and tucked away. What he found was the cable has something plugged into it—probably a ground from the stereo installation.

However, we can’t be certain as Dan is not a stereo installation specialist, neither am I, and neither one of us installed this unit. So, it’s very possible if that cable is actually a ground cable, then unplugging it from the alarm sensor and grounding it to the chassis could resolve the high pitched tone. I’ll tell Mike about this when I head to Audio Design on Tuesday.


Back to the MAF, the replacement arrived today and I installed it immediately. It literally takes all of six minutes to install. After a while, I took the 996 out for a spin to see if the MAF really did resolve the issues I was having…


Yes, it did! It’s a night and day difference. I am completely floored by the way the car performs, even just the way the car runs. I didn’t think it was running poorly to begin with, but now… wow, there’s just so much of a difference. It’s so much smoother, more responsive, more power, no warning lights come on, it’s like a totally different car. Yes, I realize the mixture of fuel and air is incredibly important, but I had no idea such a tiny part could play that big of a role in how the car performs. This is likely going to resolve my incredibly pathetic gas mileage problem too. Amazing.

I’ll be taking the 996 back to RMG to have them run another diagnostics and clear any errors resulting from the time spent driving the car with a failing MAF. I’ll wait until after my visit to Audio Design for that though, just so everything is well sorted.

It’s nice to know that after I stop by Audio Design, then RMG, that’s really it. Everything I’ve wanted, or needed to do to the car will be complete. There’s nothing left for me to do other than enjoy the car—which is exactly what I intend to do!



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