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A Mechanic's Life - Tales From Under the Hood

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Comments

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Pride in your work is a very individual thing, and I suspect instilled in an individual at a very early age. If I had used channel locks on a nut, my Dad would have knocked my head off.

    I can't do a lot on modern cars, because I don't know enough. But what I can do, I do well.

    Doc, why don't you fly out here and help me fix the air bag light on my Mini Cooper? We're having a devil of a time with it--part of the problem being that some long time ago, some monkeys got into the wiring and by-passed various connectors. The scanner gives a code for side air bag. I'd hate to have to tear into the seat as a last resort.
  • thecardoc3thecardoc3 Posts: 5,091
    I don't have to fly out there to help. I can easily figure out a routine for you and the shop to follow. BTW, it's important to point out that I've never worked on the airbag system on any Mini. But then that's the point towards all of the discussion, being able to deal with something first hand that you have never seen before is the true measure of one's talents/skill. It takes no knowledge/skill/talent at all to repost a picture/story referencing something that someone else encountered and worked through.

    What code is setting? Model/Year? Since you referenced a particular device, one of the side air bags, the first thing I would do is force the opposite code and see if the module recognizes the change in the circuit. This is a routine that I created, use and teach.

    That first step does several things. It first proves that you haven't misidentified the code. There are lots of reasons that can happen not the least of which can be mistakes in service information. It also allows you to test the module and the harness up to the test point that you choose without doing a lot of extra work.

    So, when you try to force the opposite code what can happen is:

    You get a code for a completely different circuit/component. That means of course the one that actually has the issue isn't the one you accessed.

    You succeed in forcing the opposite code. That means everything is fine from that point back towards and including the module. Choose another point to repeat the test moving away from the module towards the airbag.

    The module still sets the same code. That means the problem is towards the module from the point that you chose to do your first test.





  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Hmmmm.....clever...let me ponder this for a moment....

    So how do you force an opposite code. This is a 2003 Mini Cooper S. You may recall that the first code was for driver's side pre-tensioner. I took a working one out of another car and that just caused a new code--driver's side air bag. I have heard of one code blocking another.
  • thecardoc3thecardoc3 Posts: 5,091

    Hmmmm.....clever...let me ponder this for a moment....

    So how do you force an opposite code. This is a 2003 Mini Cooper S. You may recall that the first code was for driver's side pre-tensioner. I took a working one out of another car and that just caused a new code--driver's side air bag. I have heard of one code blocking another.

    One code blocking another occurs in other systems such as the OBDII controls, that doesn't apply to airbag systems. They treat each key cycle as it's own event.

    Now let's break down the details, first what code exactly is setting right now, give me both the number and the description that you have.

    If the code description is high resistance or open, then disconnect the wiring to the airbag anyway that you have to and jumper the module side of the harness, shorting it. Cycle the key off and back to on. If the module now shows that the circuiit is shorted, then that confirms everything is fine with the module and harness to that point. Restore the circuit and move towards the airbag.

    If the code description is that the airbag circuit has low resistance/shorted. Simply open the circuit any way that you have to, cycle the key and see if the module now displays an open circuit code.

    You can clear codes at will as you try each step too, that can help with keeping the strategy in focus.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    OK. I'll get back to you later on this. Not going to mess with it today. I'm a bit burned out on it. Thanks.
  • roadburnerroadburner Posts: 12,245
    edited January 22

    OK. I'll get back to you later on this. Not going to mess with it today. I'm a bit burned out on it. Thanks.

    The internet is a wonderful thing; back in the early to mid '90s I was the east coast tech advisor for the M Register(owners of the gray market and US spec E24 M6 as well as the E28 and E34 M5). All communication was either by USPS or phone- I spent a few evenings on a land line talking guys through various service and repair procedures, usually by standing by my own M6 for reference(I really miss that car; the S38 engine sounded glorious- especially after the catalytic converter accidentally fell off in the garage and was replaced with a Jet-Hot coated track pipe. B) )

    Mine: 1995 318ti Club Sport; 2014 M235i; 2009 Cooper Clubman; 1999 Wrangler; 1996 Speed Triple Challenge Cup Replica Wife's: 2015 X1 xDrive28i Son's: 2009 328i

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Finally fixed that damned Mini airbag light. The problem was a totally random and intermittent signal from one of the sensor wires under the seat. So ripped the seat out (again) and started tracing and.....there it was...a fraying wiring. So cut that out, spliced in a new piece, and we're good (so far). This was made more difficult by someone many years ago who changed some of the wiring under there, and obviously routed things incorrectly.
  • MichaellMichaell ColoradoPosts: 121,521

    Finally fixed that damned Mini airbag light. The problem was a totally random and intermittent signal from one of the sensor wires under the seat. So ripped the seat out (again) and started tracing and.....there it was...a fraying wiring. So cut that out, spliced in a new piece, and we're good (so far). This was made more difficult by someone many years ago who changed some of the wiring under there, and obviously routed things incorrectly.

    Congrats on your patience and perserverence on this.

    Will it be going back onto the market?

    Did you get a good deal? Be sure to come back and let us know! Post a pic of your new purchase or lease!


    MODERATOR

    2015 Subaru Outback 3.6R / 2014 MINI Countryman S ALL4

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Yep, got it on craigslist. What happened is that someone in the distant past changed the wiring and didn't use braided wire--more like cheap bell wire. Naturally this is brittle when flexed. The wire was broken inside the insulation, so the two ends would sometimes touch, sometimes not. Maddening.

    Just drove it around. It's a lot of fun, but I have to say the Volvo C30 is more comfortable, quiet and less jittery. When you threw the Mini into a turn you never knew exactly where it was going--LOL!.

  • thecardoc3thecardoc3 Posts: 5,091

    Finally fixed that damned Mini airbag light. The problem was a totally random and intermittent signal from one of the sensor wires under the seat. So ripped the seat out (again) and started tracing and.....there it was...a fraying wiring. So cut that out, spliced in a new piece, and we're good (so far). This was made more difficult by someone many years ago who changed some of the wiring under there, and obviously routed things incorrectly.

    Nice. So did my routine help you get a direction?

  • andres3andres3 Southern CAPosts: 10,957
    1) If you ruin your car doing things you "read or saw on the internet" who do you sue when things go wrong? Anyone ever see a video that would surely "sabotage" you?

    2) So I think I mentioned before that Pep Boys (the last time I used them to mount tires - and will be the last time) got 3 tires on correctly, but mounted one of the directional tires backwards. The tire even said "inside/backside" on it. The inside was placed on the outside, and the outside on the inside.

    3/4 is a 75% and mediocre C grade in school. However, for a paying customer, I considered this an F, unless of course they only want to be paid 75% of the bill.

    Should this have been a teachable moment, or was I right to consider them incompetent.
    '16 Audi TTS quattro 2.0T, '15 Audi A4 quattro 2.0T, '19 VW Tiguan SEL 4-Motion AWD
  • thecardoc3thecardoc3 Posts: 5,091
    What would the world be like if everything was one strike and you're out?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490

    Finally fixed that damned Mini airbag light. The problem was a totally random and intermittent signal from one of the sensor wires under the seat. So ripped the seat out (again) and started tracing and.....there it was...a fraying wiring. So cut that out, spliced in a new piece, and we're good (so far). This was made more difficult by someone many years ago who changed some of the wiring under there, and obviously routed things incorrectly.

    Nice. So did my routine help you get a direction?

    In a way it did, yes, thanks. Got me to thinking in isolated sections rather than the big picture--the latter not making too much sense.
  • xwesxxwesx Fairbanks, AlaskaPosts: 13,084
    Doc and/or @0patience have probably come across this in their exploits: The vehicle requires a computer system sync/process when a new battery is installed. Why is this necessary? Isn't control of the charging system just a matter of voltages and amps? I just don't quite get how *not* doing this process can put things awry, or why the manufacturer would even want to set up their vehicles for potential failure in this way.

    Also, what is a battery tender compared to a trickle charger. Someone told me that I can put a "battery tender" on the cables when changing out the battery, and this will keep me from losing the vehicle's memory settings, etc.

    Just for context, I'm starting to have reliability issues with my stock battery in the Q7, so I will probably change it out within the next few months.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • thecardoc3thecardoc3 Posts: 5,091
    edited January 24
    xwesx said:

    Doc and/or @0patience have probably come across this in their exploits: The vehicle requires a computer system sync/process when a new battery is installed. Why is this necessary

    There are functions that the car has to perform that need to be trained that don't go into non-volatile memory. Some things crank the crank sensor pick-up profile are often like that and that is important for the computer to accurately measure crankshaft accelerations in order to detect misfires. (different manufacturers have different names for that process)

    There are thousands of articles and quick guides like this one for a 2012 Toyota for retraining vehicle systems after a depower.
    http://crrtraining.com/CRR2/assets/pdfs/QT611C.pdf

  • guitarzanguitarzan OhioPosts: 817

    There are functions that the car has to perform that need to be trained that don't go into non-volatile memory.

    There is no reason to not put this data into a persistent memory, or use a CMOS battery to power the memory. For goodness sake there are home alarm clocks that keep their time while the battery is changed.

    I just learned this lesson when I replaced the battery on my wife's Mazda 3. She went shopping and stalled just as she got into the lot and began idling. Seriously?
  • xwesxxwesx Fairbanks, AlaskaPosts: 13,084
    edited January 24
    Okay, so that leads me into the second question I had.... Also, what is a battery tender compared to a trickle charger. Someone told me that I can put a "battery tender" on the cables when changing out the battery, and this will keep me from losing the vehicle's memory settings, etc.

    The impetus for asking that question was to know whether retaining memory during the battery change would prevent me from having to do a retrain on the system after the swap.

    I'm planning on investing in a RossTech unit in the near future, but I'm not sure that my planned purchase timeline for that is going to sync up with my need to replace the battery if it keeps going downhill.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • roadburnerroadburner Posts: 12,245
    I can only speak to my experience with BMW/Mini vehicles, but the battery registration requires entering the AH rating of the battery as well as whether the battery is an AGM or not. You might look into the Carly for VAG app; my Carly for BMW app lets me register a battery in just a few minutes.

    Mine: 1995 318ti Club Sport; 2014 M235i; 2009 Cooper Clubman; 1999 Wrangler; 1996 Speed Triple Challenge Cup Replica Wife's: 2015 X1 xDrive28i Son's: 2009 328i

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
  • thecardoc3thecardoc3 Posts: 5,091
    I wonder if Don Lee knows that the GM he installed in his Toyota store nixed the training group that used too be held there. The group found another venue for the classes and is still active, but none of their techs are involved anymore.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    So why was it nixed?
  • thecardoc3thecardoc3 Posts: 5,091
    xwesx said:

    Okay, so that leads me into the second question I had.... Also, what is a battery tender compared to a trickle charger. Someone told me that I can put a "battery tender" on the cables when changing out the battery, and this will keep me from losing the vehicle's memory settings, etc.

    A battery tender regulates the output voltage to the float voltage once the battery has reached full charge. If left on indefinately, it will cycle off and back on ensuring that the battery does not get overcharged. A trickle charger like any battery charger will overcharge the battery if left on too long, potentially destroying it.
    xwesx said:


    The impetus for asking that question was to know whether retaining memory during the battery change would prevent me from having to do a retrain on the system after the swap.

    A back-up battery is a better choice for this than either a tender or a trickle charger. That's not saying that they won't work but there are traps. For example if one of the doors get opened during the battery replacement, the tender won't put out enough current to support the vehicle when the interior lights come on and you will lose the memories. The trickle charger outputs more power, but it is a pulsed power like any other battery charger and sensitive electronics could be damaged by the voltage spikes that would normally be absorbed by the battery.
    xwesx said:


    I'm planning on investing in a RossTech unit in the near future, but I'm not sure that my planned purchase timeline for that is going to sync up with my need to replace the battery if it keeps going downhill.

    One of the best things about VCDS is Ross-Tech Wiki http://wiki.ross-tech.com/wiki/index.php/Main_Page

    I do need to update to the newer pass through https://store.ross-tech.com/shop/vchn/ but for now my Autel 908S Pro and my ISCAN WT2 fill in when needed.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Doc, you'll love this I think:


  • thecardoc3thecardoc3 Posts: 5,091
    Looks like I'd make about 20.......
  • xwesxxwesx Fairbanks, AlaskaPosts: 13,084
    Thanks, Doc; info much appreciated! An easy and obvious thing to slap a backup on the system while swapping out, and very simple to do on the Q7 since it has auxiliary posts in the engine bay (battery is under the driver seat).

    Weather was warmer this week, and the battery made it a full week without causing me issues. I put the charger on it this afternoon.
    2014 Audi Q7 TDI, 2008 and 2013 Subaru Forester(s), 1969 Chevrolet C20 Pickup, 1969 Ford Econoline 100, 1976 Ford F250 Pickup
  • thecardoc3thecardoc3 Posts: 5,091
    Saw this today, need to have this on a T-shirt.

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Doc, have you ever used Identifix?
  • thecardoc3thecardoc3 Posts: 5,091
    Not in the practice of servicing vehicles. I am familiar with the service, I have taught some classes that emphasized it's use so I had to become familiar with it. But, professionally I have always had a problem with how it is usually marketed and used. If it is used as a silver bullet source, it effectively results in the user guessing what is wrong with a car and that normally results in someone throwing parts at a repair. If someone uses it to find out how to test and prove what is wrong with a car, that's fine, but with the right training and skills a good technician simply doesn't need it. The only thing that is needed is accurate service information and the tech will find his/her own way.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    I have heard of some shops using it as a way to show customers that the recommended repair is legitimate and logical, and that some cars have such common faults that the Identifix list is a mile long.
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