My '01 E55 has ~110,000 miles on it. Started running very rough recently. Terrible gas mileage and throwing a 0100 code consistently (erase it, starts up without it, then comes right back).
Has anyone had any experience diagnosing a 0100 Code (MAF or VAF A Circuit Malfunction)?
Replaced the MAF about 12,000 miles ago (whole thing with a Bosch part; not just the insert). Since I started getting the 0100 code I took out the MAF and cleaned it with CRC MAF cleaner (didn't take the MAF apart).
That code is for the MAF circuit and usually a MAF malfunction triggers the P0170 and P0173 codes. However, I posted a test for the MAF (requires an VOM, basically blow on the wire and watch resistance) so you could try that. And certainly inspect the wires to the MAF, make sure they're good and the connector is clean and fully inserted.
That said, trying to clean the important part of the MAF while leaving the insert in place in the assembly is sort of like taking a shower with your clothes on. You might get some soap in where you need it, but you certainly won't do the job you intended. So that's certainly worth a try. In fact I'd probably pull the insert, run the diagnostic with the VOM and if it reads good, clean it and put in back in.
You mention mileage but not other maintenance. At that point you should have done plugs and all four of your O2 sensors, any of which could account or contribute to poor mileage and driveability.
Take care and enjoy the ride,
Greg
__________________ If the only prayer you say in your life is thank you, that would suffice. Meister Eckhart
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Thanks for the quick reply, Greg. Have not done plugs, wires, or O2 sensors. Yes, they are on my list.
I agree that I did not give MAF a true cleaning. I planned to, but when I took it out I could not get the insert out. This puzzled me for a while because I just couldn't get my T-25 security torx bit to fit. Then I figured out that my MAF screws are some kind of 5-point-star, security "torx" screw (whereas my bits are a 6-point-star set). I don't quite understand this because I have read several posts about cleaning the MAF and I thought I had the correct tool. BTW...the MAF is a Bosch that I bought through AutohauzAZ.com.
Also of note, the performance and mileage problems were not a gradual decine. Basically, the car was running great (19.6mpg all-city driving) and all of a sudden (during a short WOT run) it stalled out, CEL came on, and it has been running like crap ever since.
I guess I'll try a more-thorough cleaning and the voltage test. I'm hesitant to just plunk down another ~$200 on an MAF since it seems like 0170 and 0173 are the more common codes for that.
Apparently this is my problem with getting the MAF apart. Excerpt from Wikipedia:
A TORX variant, TORX PLUS, is designed to allow greater torque, and to minimize wear. Currently, TORX PLUS heads and drivers are patented, slowing adoption in the marketplace. Standard TORX drivers can be used to drive TORX PLUS screws, but TORX PLUS drivers will not fit standard TORX screws. There is also a tamper resistant version of TORX PLUS, having five lobes and solid post in the center. Drivers for the tamper-resistant version are tightly controlled by Camcar, and are sold only to OEMs (along with the fasteners), or OEM-authorized repair facilities.
Apparently this is my problem with getting the MAF apart. Excerpt from Wikipedia:
A TORX variant, TORX PLUS, is designed to allow greater torque, and to minimize wear. Currently, TORX PLUS heads and drivers are patented, slowing adoption in the marketplace. Standard TORX drivers can be used to drive TORX PLUS screws, but TORX PLUS drivers will not fit standard TORX screws. There is also a tamper resistant version of TORX PLUS, having five lobes and solid post in the center. Drivers for the tamper-resistant version are tightly controlled by Camcar, and are sold only to OEMs (along with the fasteners), or OEM-authorized repair facilities.
Hi, Ed.
If you go read the DIY I did on cleaning, it notes that you can just use pliers (I used needlenose visegrips) to grasp the edge of the shoulder on the screw and remove it that way. Not pretty or perfect but it does work well. I wouldn't just remove the insert for cleaning, though, I'd connect up the VOM and follow the Bosch test to see if it's working properly. I agree no reason to plunk down money again, thus the test procedure.
Once tested and cleaned, you can always do the car reset procedure to return most things to baseline, then go on from there.
Thanks for the input. Greg, I saw that in your post about gripping the screws with the pliers. However, I'm limited on time right now (this [i]work[i] thing is getting in the way), so I ordered a replacement MAF from AutohausAZ.com ($181.00 with free shipping...I'm in AZ so I have to pay sales tax). I'll pop that in tonight and see what happens. If that corrects the problem then I'll try sending the first one back to Autohaus as a warranty return since I bought it less than a year ago. If not, I'll be able to mess around with it...
I have the Torx Set referenced above; those are 6-point Torx. The screws on my MAF are the 5-point Torx per my post above about the "Special OEM" Torx.
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