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June 15, 2007

That OBD II code has become the bane of my existance.  Last week, Leslie’s Audi A4 alternator gave up the ghost after 130,000 miles, and I sucessfully replaced it.  Though that operation was more complex than it needed to have been, it saved me a trip to the dealer, and should have been the end of the story.

But alas, this has not been the case.  During the repair, I disconnected the battery to avoid troubles, and as step one in virtually all repair instructions.   That may have been my fatal mistake.  I now have a car that will barely idle, and will not drive.  Diagnostic code set is P1545 – which is a throttle position sensor error. 


I don’t believe the sensor suddenly went bad, and unplugging it, changes the code to P1544 which shows correctly the sensor is out of the loop.  I have two friends in the mechanic trade with access to “Alldata” the all knowing, master troubleshooting and diagnostic proceedure based online service.    Calling in some help from these guys, with their more expensive, and capable scan tools than the one I have above, we are able to discern the sensor does change voltage when actuated, but the car’s computer, the “Motronic ECM” does not output data relative to this sensor in the data stream.  The two just aren’t talking to each other.   In fact, that’s clearly explained in the trouble shooting flow – that the car may need to be taken to the dealer so that they can use their proprietary scan tool to resychronize the throttle position sensor to the car’s ECU.

How can this be?  In talking to my friends, they tell me it’s only getting worse.  While this ’99 model year car uses the OBD II, or On Board Diagnostics II generation computer systems, models of cars into this century now have multiple computers networked together on a CAN Bus, and use wireless communications to actuate power window and other controls.  In fact, just this week a 2007 model year truck, who’s battery died had to have it’s computer system completely reflashed, the equivalent of reloading Windows on your laptop computer, just to get it to restart, turn on the radio, roll down the windows, or start up the DVD navigation system.

Are automakers designing this way to increase the revenue stream from non-warranty services?   The computer industry has certainly recognized that there is higher profitability in services that hardware.  IBM has liquidated it’s printer, storage, and PC hardware divisions while growing it’s services and consulting division through aquisitions.

Looks like I’m not going to be able to escape the dealer after all.  I’ll load up the car and drop it off over the weekend, so they can get this resolved Monday.  Should be about a 10 minute job that probably books at least an hour of labor.


I hauled the car to the dealer last night and dropped it off.  Luckily, they were closed and didn’t see my defeated look as I rolled it off the back of the truck and into the service lane.   We filled out the key drop off, and I got a call today by 10 am.  All fixed, $115 please.  It was just a calibration using their VAG tool as I guessed.  To soften the sting, they advised they had washed and vaccumed the car for us.  There is really a lesson there on service – getting your car back clean and fresh smelling plays well to the psychological perception that your condition has been improved by the money you just spent.  You feel you got more “value”.    

6 Comments leave one →
  1. June 16, 2007 3:16 am

    Ouch, I’m sorry to hear that Mark.

    From what I’ve heard, embedded systems is a REALLY hot market in engineering right now. Guys who can program multiple indepedent, and relatively simple, processors to handle the bajillion computerized tasks that are in cars today are in high demand.

    Hell, some factory audio systems come with hard drives to store your music. Gone are the days of carbeurators and mechanical speedometers, we are now at the whim of Bill Gates in our cars.

    I for one don’t care for the electronic throttle in my LS2. There is a noticeable lag between on & off throttle. While you’re already on the throttle, the adjustments are extremely precise and you can feel it, but I can’t say that aspect is any better (or needs to be any better) than a cable-actuated throttle.

    Note to self: don’t buy an Audi.

  2. Nicholas permalink
    May 24, 2008 6:13 pm

    Hi Mark,

    I’ve in a very similar predicament. I cleaned my 2000 Audi TT Throttle Body and since have purchased a new one, at a cost of 400 Euros – about $600 my car still won’t idle correctly. It keeps coming up with the same error!

    Do you possibly have any idea what calibration they did as my car has been in a local garage for over 10 days and they are still scratching their heads as to what the problem is.

    I would really appreciate any help you can give me.

  3. May 25, 2008 3:20 am


    I can’t say specifically what the process is using the VAG tool to reassociate the computer with the TPS sensor.

    As a side note, the car developed a failure of the mass airflow suddenly last month and has been since parked. It would work fine for a few mins while cold, then once it warms up it throws a MAF code, won’t idle and driveability is so poor one can’t get out of the driveway. Part cost is about $200 through one source I have, and in the mean time, I found a new Bosche MAF on ebay and bought it for $60, however I find it is a 5 pin plug and my car has 4 pins. So, I’ve got to exchange the part.

    On your situation, the local garage must have the deal VAG tool or they won’t be able to correct this. Sorry to be the bearer of bad news.

    Let me know how it comes out. I’m working a new post on the MAF debacle

  4. David P. permalink
    May 4, 2009 7:26 pm

    Hey Mark,
    Sorry for resurrecting this post (again, it seems!), but I’m having the exact same problem with my ‘99.5 A4 2.8. Car was running fine one day, the next the battery was totally dead. Jumped it, and was able to drive for a bit to charge, but was having drivability issues like what you describe (idles OK but severe power loss, can’t keep constant revs at 1.5-2k, won’t make it over 25mph). Had it towed to my local guy, who charged the batt and says battery and alternator are A-OK (my initial concern), but still has running issues. He pulled code p1545, but I told him to hold off on exploratory surgery until I made up my mind on whether to bring it to a dealer. Is this something that is just a calibration issue as you described, or did they need to replace the throttle body, TPS, or anything else to get it to work? Thanks for your time,


  5. May 4, 2009 8:56 pm


    It is possible that the computer and mass airflow sensor have become dissociated. If this is the case, it will require a trip to the dealer to get these reprogrammed.

    Given the issue started right after your battery failure, I would suspect this is the case. Your local guy could try cleaning the MAF with some spray cleaner and clearing the P1545 code. You can then try to test drive the car (don’t go far). The code will return, along with terrible drivability within 5 mins of driving. If this is the case, I’d go to the dealer to get it reset.

    I doubt the sensor went bad at this point. Mine was probably not bad, but I had replaced it in the course of my problem determination before I found out that the computer can forget how to deal with the sensor.

    Most of the part chains can’t get the sensor, and those that can will most likely source it from World Pack, and the wholesale price will be around $200.

    I would plan to pay about $100 for the dealer to reset and recalibrate the system.

    Sorry to hear you have encountered this too…

  6. Greg permalink
    June 26, 2009 3:33 pm

    Hey thanks so much for your tips!I ran my radio for too long the other day and had my 99 A4 1.8t go dead. After charging the battery My car would start but have the same symptoms that you were having,low idle,running rough and could not drive it. Fault code p1545. I guess now I have to bite the bullet and take it in to Audi to have my tps recalibrated to the ecu.Thanks agian you saved my bacon!

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