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A Mechanic's Life - Tales From Under the Hood



  • thecardoc3thecardoc3 Posts: 1,521
    So $19 retail, which means Rock Auto paid maybe $10 bucks a piece, and Wagner paid 'somebody' a few dollars to make it, and then somebody had to dig out the raw materials and turn it into metal

    At one of the big annual trade shows there were parts suppliers selling radiators, rotors, brake pads, (and everything else you can think of) by the shipping container. The prices got lower depending on how much warranty risk the buyer was willing to assume for the parts. At a 20% risk those $20 brake rotors were costing the warehouses about $5 each. Any idea how many brake rotors fit in a shipping container?

    For the parts store that 20% risk is apparently acceptable to make that kind of profit, for us it is totally unacceptable. We need to go with the best that we can find and so our prices reflect that. Then a customer sees an advertisement from the parts store, see's what we charged for a quality part and doesn't know that there is a real difference between the two and feels that we are gouging them. :sick:
  • thecardoc3thecardoc3 Posts: 1,521
    Yea, the tail gate. Studying the schematic, the BCM sends power to the washer pump for the rear gate, and the column switch grounds it. Checking there was no power to the washer pump from the BCM. With power jumped in, the switch could control the washer pump.

    All three powers for the rear module were good. All of the power inputs to the BCM checked good.

    All of the grounds for the BCM checked good.
    The ground for the rear door module also tested good.

    Toyota has you manually power and ground the wiper motor to be sure that it isn't bad, and "if" you would have done that it would have operated, the same thing goes for the rear power window.

    So was it a bad BCM or a bad rear door module?

    Don't be so quick. The schematic showed communication (mplx for multiplexed) on a purple wire with a white tracer, pin 18 at the door module, and pin 7 at the BCM. A varying voltage of around 3v was found at the door module pin 18. Pin 7 had a yellow wire with no unique tracer, as did 5,6,8,and 9 in the BCM connector on the front of the fuse block that the BCM is inside of.

    The fuse block and BCM also have mating connections so it appeared that the communication wire must connect to the back side of the assembly. Taking apart the dash sufficiently to remove the box, the harness from the rear of the car to the BCM was finally located, the pin 7 with the yellow wire went to a similar connector that was behind the fuse block and mated to one that had the purple wire with the white tracer.

    Pin 7 did indeed have a varying voltage, but it was closer to 5v, than 3v. Voltmeters don't update fast enough to properlly display digitial communication waveforms so the correct tool is an oscilloscope. Connecting to pin 7 at the BCM normal digital communication waveform could be seen and it repeated every 20ms. It was an 11v amplitude signal. At the rear door, you saw two short bursts about 20ms apart, then nothing for the rest of that second. For each end of the purple with white wire to have different voltage patterns that can only mean that the wire had broken inbetween the modules. Attaching a jumper wire to test system operation and audible click was heard. That click was the relay that sent power to the rear washer pump from the BCM, and rear door operation was restored once communication was taking place.

    This all means that if someone would have replaced either module, they would not have fixed the car. Toyota's method of diagnostics has a tech substitute known good parts to try and they would have failed. But do you realize at this point what you don't know yet? Where is the wire broken between the two modules? Does what ever happened to that purple wire affect any other wires? Even though the system is diagnosed to that point, the diagnostics are not final yet. You still have to locate and repair the exact problem and that means the carpet may have to come up in some areas of the interior, and maybe even the headliner may have to come down.
  • thecardoc3thecardoc3 Posts: 1,521
    Our mailman asked for some information thursday. His wifes car seems to have a transmission issue. He described the engine speeding up and they couldn't go over 45mph, but it wasn't "slipping" that he could tell.

    Basically he described the transmission stuck in one gear, it's probably in limp in mode, or failsafe as some like to call it. Limp in mode is the gear that the transmission operates in when there is no command from the PCM/TCM to any of the solenoids.

    Friday. After reparing the tail gate, and doing a mobile diagnostic for another shop on two Jaguar no-starts I was back at the shop and working ona BMW that is setting misfire codes on all cylinders, but it doesn't have a misfire. While doing some reaserch on the system the mailman came in and asked for more information for his wifes car. It turns out this problem started when a back yard guy who works from his house in the evenings was trying to solve a misfire on her car. He has had the car for more than a week now and is driving it when he can with the hope that the check engie light will come on and then he can run it to auto zone and have them pull the code and tell him what's wrong. So far they can't seem to pull any codes....
  • I've often been curious about that---sometimes we'll read about a car misbehaving badly.... RADICALLY badly, and not a trouble code to be found. Is that really possible? I mean, I know that some components do not throw codes but the symptoms I read suggest that in those cases there should certainly be codes present.

    I wonder if the type of scanner some people are using just can't read everything?

    Of course, this takes us to the axiom: "Any machine is only as good as the person using it".
  • Stever@EdmundsStever@Edmunds YooperlandPosts: 38,949
    Yeah, what tool do you use to diagnose a bad OBDII port? :shades:
  • Well the scanner should tell you if it's not communicating but it can't tell you WHY it's not communicating.

    I think automotive design took a bad turn when it started all this multi-plexing. Tracking electrical issues is very tricky now.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,350
    Sounds like a "walk in the park" job for a Wal Mart mechanic...right?

    No...wait...they would have sent that job to you AFTER installing the 59.95 battery.

    Seriously, that sounded like one miserable job. Hard to make a profit on a job like that!
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,350
    Has the quality of Moog suspension parts gone downhill?

    If so, that is a real shame. They used to make ball joints, tie rod ends, idler arms etc that were far superior to the OEM stuff. It used to be that replacement Moog front end parts would outlast the rest of the car.

    What happened?
  • roadburnerroadburner Posts: 6,015
    edited November 2012
    Need brakes, as the pads were pretty well done. No other issues though.

    I just had that done on my son's X3. I serviced the rear brakes in the spring and my service advisor told me that the rotors were fine and that it only needed pads. I brought it back to the dealer this week and the front rotors were below the minimum, so I did go ahead and replace them. I appreciate the fact that my advisor doesn't go overboard but still makes logical recommendations.

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • roadburnerroadburner Posts: 6,015
    Brand new rotors can be had for less than $20 each making it a no brainer.

    Not for any performance car that I know of; the cheapest decent aftermarket rotors usually run from @$60 up.

    2009 328i / 2004 X3 2.5/ 1995 318ti Club Sport/ 1975 2002A/ 2007 Mazdaspeed 3/ 1999 Wrangler/ 1996 Speed Triple Challenge Cup Replica

  • thecardoc3thecardoc3 Posts: 1,521
    Yeah, what tool do you use to diagnose a bad OBDII port?

    The one on your shoulders.
  • thecardoc3thecardoc3 Posts: 1,521
    the symptoms I read suggest that in those cases there should certainly be codes present.

    As mentioned on another response. The PCM really cannot test past it's connector. The engineer's write sensor limit specifications, such as the TPS should not go below .5v, and if it does, the PCM sets a P0121, and the TPS should not go above 4.8v and if it does the PCM sets a P0122. If the TPS falls between those ranges, but is falsely varying (spiking up or down) then you get into the realm of rationality testing and the PCM needs time to compare the TPS voltage changes with other parameters. Keep in mind if they allow it to code too fast, then they could have issues with false fails and check engine lights when there is nothing wrong with the car.

    I wonder if the type of scanner some people are using just can't read everything

    That is absolutely at play here. It's also one of the reasons many shops supported the R2R legislation, the aftermarket tools would support about 50% to 70% of what someone might need to do with engine performance, and maybe not support specific systems at all. The 4-Runner mentioned, that multiplexed system was never designed to work with any scan tool, not even the factory one. (which I have)
  • thecardoc3thecardoc3 Posts: 1,521
    Well the scanner should tell you if it's not communicating but it can't tell you WHY it's not communicating.

    I have written and teach classes on how to perform such diagnostics.
  • thecardoc3thecardoc3 Posts: 1,521
    Seriously, that sounded like one miserable job. Hard to make a profit on a job like that!

    I'll make more money by documenting every step that I took with a camera and by saving the voltage waveforms and testing points as well as explaining the strategies involved than a customer is willing to pay for the time required. That's why people like to resort to shot-gunnng parts. It takes a lot of discipline to resist the try-zee's and actually perform the steps that are required.

    It will take me another ten hours to produce the case study from the information gathered by that one repair, but if I can sell it, it will help subsidize the shops existence and maybe even pay for one of my software updates that I need.
  • obyoneobyone Posts: 8,065
    Hm, Wagner fronts are $19 at RockAuto, Raybestos are $27. Don't think I need the $199 drilled and slotted ones on the '99 Quest.

    Yep and ordering the parts through a shop will get you a 25% discount on those prices. I always go with both Raybestos rotors and ceramic pads and never had a problem.
  • obyoneobyone Posts: 8,065
    Changing vehicles every 2.5 years is likely costing you about $7500 a year depending on what your buying. Imagine doing that with a $40,000 pick-up like some companies now face doing. Now sure, service costs increase the longer you have the vehicle but it really is only nickles and dimes to fix what you have compared to hundreds to replace it.

    For the record I have a '99 C5 which does around 3000 miles a year and costs over $1000 a year to insure.

    2010 GMC Acadia
    2012 Nissan Titan SV (which they are giving away)

    I changed out the pads on the Titan at 150 miles cause that black dust caused by the stock pads just didn't work for me. Didn't change the rotors cause it hadn't shown much sign of wear. No squeaks so far. Changed the shocks out at 200 miles replacing the stock ones with Bilstein. I wouldn't call these performance upgrades rather making the truck more livable.
  • obyoneobyone Posts: 8,065
    edited November 2012
    $165.00 on an alignment? a good friend of mine owns an alignment/repair shop. A four wheel alignment costs $75.00 on most American cars. Is there anything special on an Escort that would double this price? Just curious.

    For the record he charges $175.00 to align an E500 not cause it's any harder but because the owner expects it. Anything less would be suspect by the owner.
  • xwesxxwesx Fairbanks, AlaskaPosts: 8,268
    Just the area - everything's a mint around here. The shop is also the best in the area and has an excellent reputation, so you end up paying ~40 more for it. I've had several alignments from other places, but this was my first there. It was new-car perfect, and he wouldn't do the alignment until every part he indicated was suspect was replaced. A year later, and the alignment hadn't changed a bit.

    This car was also a bit of a pain on the front end because it has very little built-in adjustment options. If you have to realign it, it means bending, shimming, etc. I don't know if that played into the price, but the other shop I inquired at (which had done alignments for me previously) wanted $125.
  • srs_49srs_49 Posts: 1,394
    Replacing modules to diagnose a problem is really an acceptable troubleshooting techniques. We use it a lot in my line of work. But, what is not acceptable in the example you gave is charging the customer for those modules. Once you've found that the problem is in the interconnects, the original modules should be replaced and not charged to the customer.

    BTW, why was the wire open? Had the wire been damaged somehow? Was there a problem at the connector?
  • marsha7marsha7 Posts: 3,661
    "So they'll go to the neighborhood shyster lawyer who will write a demand letter for $500"

    Who would do such a thing?... :blush: :P ;)

    BTW, I assume the cost of rotors has gone down simply because the hub is not longer part of the rotor, but stays on the car...when they did the brakes on my Crown Vic, I was surprised to see the front rotors on the car like the they weigh a lot less...those older rotors with the attached hub weighed many not drop one on your foot...

    As far as brake drum/rotor lathes...years ago, in Dad's machine shop, we were the only ones who could cut rotors and drums with our super-duper heavy duty machine...over the years I have seen much smaller lathes in service centers that would only have a small capacity as they sat on a workbench, but probably enough capacity for the one shop's brake work...those machines probably worked well and paid for themselves, esp when they actually put an extra 1/4 inch of iron on each rotor (weigh be damned)...then, when they (carmakers) realized that they could shave some weight by installing rotors with just a few thousandths of material over the minimum safety standard, it almost made those smaller brake lathes obsolete, not because the machines were bad, just that mechanics hardly could trim off a few thousandths before they were in the "unsafe" zone for brake rotor thickness...

    In other words, some rotors became un-trimmable, and only replaceable, so if you needed a brake job, it now included new pads and NEW rotors, rather than cutting 10-20 1000ths off the rotor, which made it too thin for safe stopping...
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