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Wednesday, April 23, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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November 11, 2006

Meow. Meow.

I left work a few minutes earlier than usual on the evening of election day to make sure I got to the polls before they closed. I was about 10 minutes into my trip, doing about 75MPH, when the "cockpit" was suddenly illuminated by a bright "Check Engine" light (CEL) in the gauge cluster. The car continued to run fine so I maintained speed and issued a request to pull my BMW troubleshooting mental subroutine from main memory and execute it. Fortunately, I'd used it recently so I got a cache hit and it loaded far faster than I expected (hey, I work with computers all day...why should this process be any different?)

At first, I considered the very real possibility that the incumbents had tampered with my vehicle so I wouldn't make it to my polling location in time to send them packing, but I ruled that out because I realized they lacked the intelligence required to sabotage anything but the federal budget and foreign policy. After I caught that exception and dismissed it, it didn't take much additional processing for the routine to spit out the most likely cause -- something to do with the catalytic converters or the post-cat oxygen sensors that measure cat efficiency. My technician had pulled that code a few times before, but the most recent state emissions tests demonstrated that the Cats are doing their job -- very well, in fact. There wasn't much I could do about the problem that evening, so I decided to continue on to the polls, do my part to save our democracy, and then head home.

The next morning I went to the dealer to find my technician away at school. Some other helpful techs pulled the codes and confirmed the CEL was flagged as a result of "Low Catalytic Converter Efficiency". Damn, I'm getting good at this stuff! They cleared the codes on my request to extinguish the annoying idiot light and told me my tech would be back the next day. Roughly 24 hours later, I showed up to give my tech the rundown and get his opinion.

I speculated aloud that the reason the code generated a CEL this time was because I did the oil change last time and the car simply hadn't been in his bay in a while. You see, although checking and clearing codes is not officially part of an oil service, my tech usually takes care of that because he likes to be thorough and notify customers of potential problems. This is important, because as I've pointed out before, many errors reported by the OBD / DME / TCM have thresholds, and will not necessarily trip a CEL if they occur. It may take two or more occurrences to trip the light. Since my technician didn't have an opportunity to clear any codes recently, there was probably an older code in the system and the election day event sent it over the threshold and triggered the light.

When I asked whether this was typically an oxygen sensor problem or really a Cat issue, he said with 135K miles on the clock, it was most likely a failing Cat. He also said that if I did need a new Cat, I'd be well advised to buy OE. With a knowing look on his face he warned me "...aftermarket cats just don't work on BMWs. I've pulled a lot of aftermarket junk off these cars." While I'm not looking forward to spending $1500, I am fortunate in that the 328is has the Cats in the mid-section of the exhaust rather than the headers, so replacing the Cats is as easy as dropping the exhaust from the headers back. My tech mentioned that the job is pretty straightforward and he recommended that if I decided to do it myself that I don't bother with disconnecting the rear and mid-sections of the exhaust -- just disconnect from the headers and drop the entire assembly down -- because it's a lot easier to deal with the bolts that connect the rear and mid-sections when they're out from under the car. Good news for when (not if) I need to do that.

It's been a few days since that problem and I haven't seen the CEL again. However, while driving today I managed to trigger another warning I'd expected to see several months ago -- the brake lining warning finally tripped after 48K miles on the fronts and a whopping 73K miles on the rear. It's very likely the front sensor tripped the warning, but I'm planning to do all four corners. If all goes as planned, I'll do the brake job tomorrow and get the car back on the road for my commute on Monday.

Technical Management

The past week brought some surprising news at my dealer. I'd known that my techician was expecting to retire from the business entirely in a few years, but he pulled me aside and told me that around the first of the year he'll be hanging up his torque wrenches and assuming his role as shop foreman exclusively. He said that in most BMW shops the foreman doesn't "work the line" as we pilots say, so this is really "the way things are(tm)".

After he got up off the floor and finished massaging his sore jaw, :-) I asked him "well, if you're not going to work on my car anymore, who do you recommend here? Obviously...I want someone who knows his trade like you do and can read between the lines of diagnostic codes on the GT1 for the best solutions to my problems." He quickly pointed someone out and in doing so named his successor.

I then pointed over at my tech's gigantic tool chest and the thousands of dollars worth of tools contained therein. "Hey, can I have those? I mean, you won't be needing them anymore, right?" His response was predictable. "Uh, I don't think so...I'll be using them soon enough if this management gig doesn't work out." Oh well. I tried. So it appears I'll be making a few more trips to Eppys after all.

Mileage: 135200.