bircham Posted August 31, 2009 Report Share Posted August 31, 2009 Hi again, Got my vag-com shareware version working with my 1999 FL A8 3.7 quattro and was looking for a way to get the DIS lights to show the correct gear, instead of all showing up red. When I ran a check on the trans it showed up as fault 18158 - supply current too low. I cleared the fault and the DIS lights returned to normal. Hopwever, on starting to car agin the red lights had appeared again. I ran vag com again and the fault code had appeared again. Does anyone know what that fault is? It drives me nuts at the random nature of the lights coming on and off and it would be great to be able to get them back to normal permanently! (if that's at all possible.) Any help would be greatly appreciated, Jon Link to comment Share on other sites More sharing options...
scotsman50 Posted August 31, 2009 Report Share Posted August 31, 2009 On my dedicated VAG handheld unit the DTC code you give is explained as FUSE,WIRING TMC dont know if this is of any help to you also checked it in the code database on my laptop unit same reply Link to comment Share on other sites More sharing options...
bircham Posted August 31, 2009 Author Report Share Posted August 31, 2009 thanks scotsman50, would this be something to do with a fuse then? i have also found out that it as something to do with a reduced low voltage power but to where, and from where I haven't got a clue! Any help would be great. Jon Link to comment Share on other sites More sharing options...
scotsman50 Posted August 31, 2009 Report Share Posted August 31, 2009 Fraid im no electrician but i would head for fuse and try a lower size first also could be a bulb in display taking to much power.......thats my way of thinking just thoughts Link to comment Share on other sites More sharing options...
PsYcHe Posted September 1, 2009 Report Share Posted September 1, 2009 Got Vag Codes? Wonder what they mean? - AudiForums.com has an interesting list of the codes and descriptions. That code relates to P1750 which is a transmission problem. Have you checked your battery? Also, check the point on the car where all the power connections come together at the front (driver's side near the bottom on the inner wing). Sounds like there's a problem with the gearbox not getting a high enough voltage into the system (or maybe just the TCU) and causing the error. Link to comment Share on other sites More sharing options...
bircham Posted September 1, 2009 Author Report Share Posted September 1, 2009 I'll check the battery charge and see if it is low. I'l also have a look at the power connections to see if there is anything unusual to see. Jon ps, I'll also try and post a pic of a small grey wire that I see when I open my glovebox. It was apart, but I have no idea what it is/was and if it made any differnce when I connected the two ends together again. Link to comment Share on other sites More sharing options...
Figure11 Posted September 2, 2009 Report Share Posted September 2, 2009 Check for poor earths. There is an earth cable from the drivers side chassis rail to the engin. Quickest way to check is with a volt meter. While the car is running take the voltage from the alternator to the alternator casing; should be >13V. Then ground the volt meter on the chassis. If there is a difference then you have a poor earth. Disconnect the earth cable clean, abrade and reconnect. Both engine and boot. Mike Link to comment Share on other sites More sharing options...
bircham Posted September 2, 2009 Author Report Share Posted September 2, 2009 Check for poor earths. There is an earth cable from the drivers side chassis rail to the engin. Quickest way to check is with a volt meter. While the car is running take the voltage from the alternator to the alternator casing; should be >13V. Then ground the volt meter on the chassis. If there is a difference then you have a poor earth. Disconnect the earth cable clean, abrade and reconnect. Both engine and boot.Mike Thanks for that great info Mike. I have a volt meter so I'll give what you suggest a whirl and see waht happens. Jon Link to comment Share on other sites More sharing options...
RJP Posted September 2, 2009 Report Share Posted September 2, 2009 As others have said, the gearbox thinks it is not getting enough voltage (and may not be). This could be a fuse or a fault in the battery voltage reading due to poor connections or poor earth, but could be a control unit internal fault. From elsawin (sorry I can't help with the various internal references): Fault code 18158 / P1750 Display on -VAS 5051-Possible cause of fault How to rectify fault18158 / P1750 Voltage supply Voltage too lowt Fault detected by battery monitoring systemt Battery voltage less than 7 V– Read measured value block 003 → Anchor t Open circuit or short to earth in wiring– Check wiring and connectors according to current flow diagram– Perform electrical check, test steps No. 1 → Anchor and No. 6 → Anchor t Fuse defective– Check voltage supply to automatic gearbox control unit -J217- t Open circuit/short circuit to permanent positive in gearbox control unit– Renew control unit → Chapter Explanatory notest The battery monitoring system distinguishes between four different ranges (U = battery voltage):1. U = less than 7 V: Gearbox switches to emergency running mode → Chapter2. U = 7…9 Volts: Gear which is currently selected will be maintained for about 2.5 seconds and if U (= battery voltage) still remains within this range after this period of time, gearbox switches to emergency running mode → Chapter3. U = 9…16 Volts: Voltage OK4. U = higher than 16 V: Gearbox switches to emergency running mode → Chaptert If the voltage supply from the vehicle's electrical system (terminal 30) fails, certain application values will be lost, i.e. the gearbox control unit must re-learn them the next time the engine is started. During this “learning process” the gear change quality may not be as smooth as usual Link to comment Share on other sites More sharing options...
bircham Posted September 7, 2009 Author Report Share Posted September 7, 2009 Well, I've checked the battery voltage and it seems that it might be alittle low. After sitting the car for a couple of days I tested the battery and it came to 11.99v. This is low isn't it? After a run it returned readings of 12.44v. Do you think this could be the cause of the error on the DIS? This morning the car returned to normal but then this afternoon it went back to displaying red lights on the DIS. I tried to have look at the alternator but it appears to be right at the bottom of the engine and needs to be accessed from underneath(?) Any help in the form of tips on how to check the earth would be really helpful! Thanks, Jon Link to comment Share on other sites More sharing options...
PsYcHe Posted September 7, 2009 Report Share Posted September 7, 2009 It could well be knackered... But not knackered enough yet fastf fit car batteries has some testing tips. I'd also check that the alternator is charging properly, but given that the car is 10 years old, I'd suspect battery if it's dropping that low. If it's been discharged a few times in the past, then that could have damaged it too. Link to comment Share on other sites More sharing options...
RJP Posted September 8, 2009 Report Share Posted September 8, 2009 As PsYcHe says, not knackered enough yet. In theory, anything above 9V when running should not trouble the gearbox. You obviously have that at the battery, and the alternator is also doing some charging as you get up to 12.4 V. The link PsYcHe gives has good info, although the voltages seem high - I have seen other links LEAD ACID BATTERY CHARGING INFORMATION, BATTERY TYPES AND OPERATION - SOLAR NAVIGATOR WORLD ELECTRIC NAVIGATION CHALLENGE, NELSON KRUSCHANDL, BLUEBIRD ELECTRIC LAND SPEED RECORD CARS where at 11.9V the battery is about 40% charged. In any event, if charging never gets you consistently above this a new battery would seem a good idea, but may well not solve your problem. I would suspect a more specific fault in the supply to the gearbox, or maybe the ground somewhere, but I have never played with this on mine so cannot offer any useful pointers. Possibly a quick diagnostic would be to jump start the car and see if your gearbox lights still come on. Link to comment Share on other sites More sharing options...
bircham Posted September 15, 2009 Author Report Share Posted September 15, 2009 Hi again, I've left the car unused since Sunday and when I went to check on it I saw that the DIS gearbox lights were back yto normal. I would have thought that if the problem was a low voltage to the gearbox then leving it would have reduced the likelihood of it going back to normal. Does anyone have any idea why it would be that a couple of days 'rest' might reset the problem. I reckon that if I use if tomorrow then it could well go back to being as it was, with all the gearbox DIS lights being displayed in red. Jon Link to comment Share on other sites More sharing options...
Figure11 Posted September 20, 2009 Report Share Posted September 20, 2009 I'm still in favour of an earth. easiest way to test is to put the front on ramps. Remove the engine tray and test the alternator in situe from beneath. While the engine is running, put your volt meter on the larger connector on the back of the alternator and touch the negative probe to the alternator body. You should get between 13.5 and 14.4 Volts, Then put the negative probe onto the chassis somewhere and measure the voltage. Any drop indicates a bad earth from engine to chassis. Mike Link to comment Share on other sites More sharing options...
bircham Posted September 20, 2009 Author Report Share Posted September 20, 2009 I'm still in favour of an earth. easiest way to test is to put the front on ramps. Remove the engine tray and test the alternator in situe from beneath.While the engine is running, put your volt meter on the larger connector on the back of the alternator and touch the negative probe to the alternator body. You should get between 13.5 and 14.4 Volts, Then put the negative probe onto the chassis somewhere and measure the voltage. Any drop indicates a bad earth from engine to chassis. Mike Thanks for that helpful advice Mike. The DIS lights have remained fine for the past few days so I wonder if it is an earth problem that surfaces in certain conditions/cable shifting etc. I will have a go at testing the alternator earth to see if that is the problem. Jon Link to comment Share on other sites More sharing options...
bircham Posted September 21, 2009 Author Report Share Posted September 21, 2009 While checking out why my wing mirror adjustment didn't work I found that the fuse for the wing mirror adjustment was missing. Fitted one of the spares and hey presto I now have full control of the wing mirrors, power fold and all. However, it also seems to have coincidentally coincided (try saying that after a few swift ones!) with the DIS gearbox lights behaving exactly as they should. I don't know if the fuse that I put in could have something to do with it? Anyway, as long as they work I am a happy bunny! I have also fitted the new front lower grille (also using cable ties to ensure that it doesn't come off again) that Audipartner kindly sent me and am now just hunting for a 1999 passenger side foglight grille. I have searched everywhere but no luck. Maybe a call to Audi themselves might be in order. I have also ordered a set of Bosch aero wipers for the car and am looking at getting sport springs fitted, along with 19" alloys of some sort. Christmas and birthday presents will have to change from socks to car parts! Once that is sorted then a trip to see my local smart repairer for some remedial paint work and I should be able to wax and polish without grimacing at the state of some of my paintwork. Jon Link to comment Share on other sites More sharing options...
PsYcHe Posted September 21, 2009 Report Share Posted September 21, 2009 Good news... You'd be surprised at some of the things which share fuses in a car. Glad to see you've caught the '8 bug big time Link to comment Share on other sites More sharing options...
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