Can Leds replacing bulbs on car blow up ECU's ? I'll tell you my story. - Page 1
Forum section: electronics / beginners

author: dssence
author_rank: Regular Contributor
timestamp: March 20, 2014, 04:25:52 am
content: Hi guys does anyone know of there's a chance anything led based replacing normal bulbs could potentially destroy circuits of the ECU or BSI if our cars have one.I'm asking this cause a couple days ago a friend of mine who's got a peugeot 206 wanted to install a led strip (whites) I helped him out take the 12 volts from the map dome light of the car. Everything went fine.Afterwards he started driving the car, and functionality started going down, he had no turn light signals, the stereo stopped working till the next day the car didn't turn on anymore.Well I came up to the conclusion after talking with ppl in the area peugeots 206 have a BSI controlled computer which controls the resistive load of all the circuits, and if you're actually driving more amperage from this line like was the case although the led strip didn't consume more then a couple milliamps the parasitic current loop return blown the BSI of the car.Now I wanted to add some led strips to the parking lights of my 86 , and this guy who fixes the BSI's says cars which come with leds by factory default, do come with their ECU's designed to tolerate these fluctiations in their circuits so everything works fine.If you change a bulb with a led one , you're in the most common scenario where you could blow the ECU/BSI of your car cause of these parasitc currents not being absorbed by the leds ( usually the case where the leds flicker) .So this guy told me it's possible to add leds to our cars but adding some sort of isolation of the leds from the cars circuit , with some optocouplers or drivers without getting within the circuit of the car itself.Can anyone please lead me a hand in here. about this.The person I installed the led strip on her 206 peugeot I took the voltage form the map light with a normal stereo jack cable , which I supposed wasn't going to add any resistive load, aside from that the led strip wouldn't be driving more than a couple milliamps. But then strange things started happening she lost functionality on turn lights, stereo stopped working. And now well she took the car to an electrician and he said it's mostly the BSI (body system integration something lke that).He checked the pulse exciting the cars alternator coming from the BSI and it's not there. When I connected the cables on the light bulb from the map light accidentall there was a short but I changed the fuse and that was it, nothing else. But eventually something might have happened on the BSI cause that's happening.Now going back to my car a Toyota FT 86 (Subaru BRZ). I was thinking on adding some led strips on the parking lights, these lights turn on whenever I turn on the lights from the instrument panel which you can dim. So I asked most of the ppl and they said nothing should happen about blowing the fuse cause the led strips would drive a couple milliamps. But ... But.. I'm starting to think it twice after what happened to this other car. Like what if .. these leds start to flicker or anything else. These are the ones I boughthttp://www.amazon.com/White-Vehicle-Strip-Flexible-Waterproof/dp/B00ARYTBFY/What do you recommend me ?This is the light bulb I'm talking about .. I want to replace on my car with a led strip. This bulb lights up when I turn on the backlight on the instrument panel , and it's got a dimmer to regulate the intensity.This happened to a guy who tried to replace the stock bulbs on door courtesy lights with LEDS on subaru BRZ forumQuote

author: idpromnut
author_rank: Unknown
timestamp: March 20, 2014, 11:42:27 am
content: I'm going to take a stab in the dark here, but I guess you connected the LED strip in parallel to the existing headlight bulb? So if the LED strip's resistance is lower than the headlight, then the total resistance for that circuit will be lower (a large resistance and a small resistance in parallel, blah blah). And hence, the current through that circuit would be higher.If the BIU is rated for a certain maximum current, then yes, adding that LED strip could damage it (especially if it is near its maximum design limits with just the headlight bulb).

author: Legion
author_rank: Frequent Contributor
timestamp: March 20, 2014, 02:11:53 pm
content: I'm not sure about automotive LEDs, but I know when you're messing around with 5mm LEDs you have to put a resistor in series to drop the current, as LEDs don't have a linear relationship between voltage and current. If that is the case here, I'm not sure where you'd get an equivalent resistance number for a car headlight or if that resistance remains relatively constant during normal operation.

author: madires
author_rank: Super Contributor
timestamp: March 20, 2014, 02:32:54 pm
content: Some weeks ago a friend tried to swap a broken light for the license plate with a LED bulb (proper replacement). The LED light was lit for a second or two, then went off and the driver display reported a light problem. After some experiments we've found that the ECU measures the current of the lights. For under-current and over-current the lights are switched off to prevent any damage and the ECU reports a light problem. So my friend had to replace the broken lamp with a traditionial one because the LED light didn't sink enough current to make the ECU happy.

author: AndyC_772
author_rank: Super Contributor
timestamp: March 20, 2014, 02:37:09 pm
content: It sounds as though a clear understanding of Ohm's law and the V-I characteristics of an LED are called for.I find it hard to believe that LEDs with a proper series resistor would blow a circuit designed to drive a conventional filament bulb, but I can see how it might happen. A bulb has a fairly linear V-I characteristic, but a string of LEDs with a small value series resistor has one which is much steeper. It might draw much less current than the filament bulb at 12V, but a great deal more at 14V. Both LED string and driver could be damaged.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 20, 2014, 02:49:23 pm
content: QuoteFairly well known problem - you need to put a parallel resistor to draw enough current so that the car thinks there is a bulb there.QuoteI find it pretty difficult to believe as well, I'd expect anything in a car designed to drive fillament bulbs to be pretty resiliant to overcurrent given that bulbs present (albeit briefly) a low resistance until the fillament heats up. It's also not exactly hard to believe that a fault could easily present a short.Sensing current and turning the power off if not in a "reasonable" range seems sensible enough - building an ECU which will fry itself because of a fault in a lighting circuit does not.

author: dssence
author_rank: Regular Contributor
timestamp: March 20, 2014, 03:16:02 pm
content: Quote from: idpromnut on March 20, 2014, 11:42:27 amWell in the case of the peugeot 206 from my friends , I just took the 12 volts from the map light not headlight bulb. That led strip he wanted to place in the trunk. I've used a normal audio RCA cable as I thought that wouldn't add any resistive load ( did it ?). And yes I attahed the cable to the pins of the map light pins so it was in parallel, everything worked fine when we opened the doors the led strip turned on. Something which called my attention was lights didn't turn on, when the doors were closed, it just didn't turn on the light on position (not doors open). ( though I didn't know if it was working before I attached the led strip).After we installed the led strips, my friend took his car.. and called me saying he pressed the turn signal and the stereo went off, the stop lights were not working . and so on. Until the next day the car wouldn't just work. End result he had to take the car to a dedicated electrician and the guy checked the pulse which controls the alternator , and it wasn't driving it at all so he came to the conclusion the BSI is screwed up.Now going back to my case , I own a toyota 86FT (Subaru BRZ same car), and I wanted to add to the parking light bulb a led strip to add the look of the GT model of my car, as I bought a base one and I disliked the intensity of that bulb , really ugly.That light turns on whenever I turn on the knob for hte instrument panel from the inside , you can also adjust the dimming from the inside of the car. So now I'm getting worried I could end up frying my BIU if I add this led strip. What should I do ?- Add a mini relay? , Optoisolate it ? honestly don't know but Idon't want to go through the hassel of blowing out the BIU . Check what this guy went through on a Subaru BRZ when he wanted to switch the doors courtesy lights.Quote

author: Yago
author_rank: Frequent Contributor
timestamp: March 20, 2014, 03:28:34 pm
content: I would have thought that adding a high(ish) current load to existing wiring is a no-no (unless you are 100% confident in information regarding wiring indicating enough headroom).Take a fused supply from the battery and switch that from the existing wiring.Interior lights are also another no-no as they often have features such as auto-dimming indicating something more complex than door switch and supply.

author: dssence
author_rank: Regular Contributor
timestamp: March 20, 2014, 03:40:57 pm
content: Quote from: Yago on March 20, 2014, 03:28:34 pmHi Yago , thanks. So in my specific case. On my car , taking into account the bulb I want to replace,with a led strip (or I might just with a led T10 bulb) is this oneThis light switches on , when I turn on the instrument panel backlight from the inside of the car. it's the light you can also dim. Would it be good If I just add the led strip there? or you would just add a relay for each bulb to the battery and then negative to the existing wiring ? supposedly I've checked the manual and it's a 5watts T10 bulb.

author: G7PSK
author_rank: Super Contributor
timestamp: March 20, 2014, 04:03:28 pm
content: A few years ago Citroen cars had to go back to the dealer for a bulb change as the cars computer was programmed for the specific bulb in the lamp and the computer would not accept a new bulb without re-programming. My father had one of these cars when a tail light blew he just changed the bulb for a like bulb but it would not work he went to the dealers and they just hooked the car up and reprogrammed it as the car was under warranty they did not charge but it was a 34 mile round trip to the dealer which is why he just changed the bulb in the first place. Would not surprise me if Peugeot is the same.

author: sigxcpu
author_rank: Regular Contributor
timestamp: March 20, 2014, 08:58:56 pm
content: As far as I know from a friend, you cannot retrofit HID lamps to a Peogeot, because the wipers will fail (BSI?). There are tons of threads on local forums on that.

author: dssence
author_rank: Regular Contributor
timestamp: March 20, 2014, 09:04:15 pm
content: So in my case what's the method for installing a led strip on my parking lights which are T10 5watts. I'm scared replacing it by a led strip will lead to failure of the BSI on my car. I own a toyota 86 FT same as Scion FRS. Should I install a mini relay? . This light turns on with the instruments backlight of the inside of the car (which I can also dim) .Which precautions should I take into consideration before replacing the T10 5watts lamp with a led strip ?Thanks again.

author: nixxon
author_rank: Frequent Contributor
timestamp: March 20, 2014, 09:14:14 pm
content: According to rumours from the 90's (when I worked part time at a gas station), French cars are more picky and dicky than "normal" cars.

author: dssence
author_rank: Regular Contributor
timestamp: March 20, 2014, 09:16:40 pm
content: So should I use this with the led strip ?http://www.carid.com/universal-bulbs/lumen-led-lights-10063403.html

author: gxti
author_rank: Frequent Contributor
timestamp: March 21, 2014, 04:31:00 am
content: No, don't add load unless you're getting some kind of "bulb out" indication. Relays seem like a safe choice since the main current would be taken directly from the battery not via the ECU, but you said that the lamps can be dimmed? If they are dimmed it's possible that the relay will not actuate correctly.

author: SL4P
author_rank: Super Contributor
timestamp: March 21, 2014, 05:26:34 am
content: I wasn't too thrilled to read......took the voltage from the map light with a normal stereo jack cable...This is fraught with danger - the worst problem being plug-in, or plug-out with DC on the connector when the tip slides against the ring/sleeve.

author: dssence
author_rank: Regular Contributor
timestamp: March 21, 2014, 05:42:21 am
content: Quote from: SL4P on March 21, 2014, 05:26:34 amWhat do you mean ? the tips were not sliding at all.

author: Neverther
author_rank: Regular Contributor
timestamp: March 21, 2014, 09:42:45 am
content: 3.5mm stereo audio jack? Secured and didn't rattle loose?Another nice thing to know would be if it was measuring current on supply or return path. That might explain if there was some backwards ground leak problem.If the system cannot handle little unbalance and faults, big ones just should blow the fuse, I don't want to know how long it is designed to last.There has been one French car in the family, not anymore and never will be thanks to that experience.Personally I drive 90s bulletproof miracle made in Italy. From times when the car was designed to be easy to maintenance and repair (except they put engine so big in it you normally need to drop engine for cambelt change, but you can cheat it).Bonus points for no emission c**p at the factory so body is fully galvanized and protected unlike todays products.It has lights out indicator but I've added trailer to it just by stealing from rear lights and it is been OK.Interior lights dim with PWM, interior fan works with PWM, injectors work with synchronized PWM, dash lights are done with rheostat, Italian electrics and still working (I hope I didn't just curse myself).</rant>

author: SeanB
author_rank: Super Contributor
timestamp: March 21, 2014, 10:02:44 am
content: Could be worse electrics, like Lucas ( the prince of darkness) as used by Ford, Rover and Leyland. Famous for inventing the intermittent screen wiper. The French have a love of "Tool, Special" for doing things. Once they make a tool they design cars around them.

author: mc
author_rank: Regular Contributor
timestamp: March 21, 2014, 10:27:41 pm
content: I meant to reply to this thread yesterday, but only just remembered about it.Car body computers (BCM/BSI/CJM/VCI/whatever the manufacturer wants to call it!) can be pretty tempremental things, especially on slightly older cars. Two things most of them hate, is anything that can put a surge into the system, or anything that causes a constantly changing input/output when it should be relatively constant input/output.A few examples I've personally came across-Ford Focus central electric modules of a certain age would partially lock up when the tailgate wiring snapped causing an intermittent connection to the door open switch. Disconnecting the battery and reconnecting it would cure it, until it locked up again, at which point we finally found out why.Had an issue where a driver put the wrong bulb into the tail light on a Ford Mondeo with electronically fused outputs to the lights from the Central Electric Module, which refused to start working until it had been disconnected for a good few minutes (they should self reset by turning whatever light off/on, but it took being disconnected for ~5min before it would work again)And just this week I happened to have an issue with a Ford Transit with random instrument cluster warning lights flickering on whenever the side lights were turned on, after the driver managed to blow all the side light fuses due to a faulty trailer socket. That took unplugging the instrument cluster itself to reset, after disconnecting the battery for 10 minutes made no difference (all the warning lights are controlled via a CANbus from the BCM, and I'm guessing it took actually triggering a fault on the CANbus for the two modules to start talking nicely to each other again)I know all those examples are Ford, but I have had issues with other makes, it's just I can't remember the exact details.What I'm getting at, is body computers can be a bit 'tempremental', so I could invisage connecting a non-resistive load (I'm going to guess the LEDs fitted will have some kind of switching supply) to a normal bulb output could cause issues.To the OP, did you try disconnecting the BSI for a good 30minutes?Quite often disconnecting things and ensuring they've had time for all stored power to dissipate, forcing them into a full reboot will cure anomolies.

author: dssence
author_rank: Regular Contributor
timestamp: March 21, 2014, 10:38:05 pm
content: Quote from: mc on March 21, 2014, 10:27:41 pmHi MC thanks so much for such a complete answer. To be honest with you I didn't touch the car anymore. Cause my friend .. was kind of annoyed not with me but with the fact that such a simple led strip would screw up the BSI. Then I came across some peugeot forums saying how to reset the BSI. The electrician guy who worked to repair his car said the BSI wasn't sending the exciting pulse to enable the car alternator so something might have screwed up there.I honestly just wired the led strip to the maplights in parallel. Firstly I did a short circuit stupid me trying to hook up the cables as I didn't solder them as quite a bit of a complication to get the car to a place where I could have all my stuff. So I was indeed sure then everything was hooked up fine.So honestly I don't know maybe the BSI from peugeot doesn't tolerate some more load on this specific circuit. I can't understand.So now going back to my case, I own a toyota 86 FT same as SUBARU BRZ or SCION FRS, I wanted to replace parking lights bulbs which are a T10 5 watts.. they turn on whenever I switch the instrument panel light which you can also dim. So I want to replace these 2 bulbs which are inside the headlamps casing next to the low and high beams (which are halogen).My worrying is .. I'm now thinking it twice if I place a led strip if this would in fact cause any bounce signal back to the BSI of my car and again damage it. It shoulnd't but.. I want' to take any precautions (adding relay for a led strip? hmm sounds useless cause how much could this led strip drive 600Mah ? maybe less, should I test the amperage it drives outside with my dmm ? )SO I see you're kinda into it you got a bit experience than me , what would you recommendme?These are the lights I want to replace with :

author: mc
author_rank: Regular Contributor
timestamp: March 21, 2014, 11:22:30 pm
content: Stick with what you've got?I don't know what country you're in, however within the EU swapping a filament bulb for an LED can have legal issues. The lamp/reflector assembly is designed and type approved for a filament bulb emitting light in most directions to provide the legally required range of visibility. When you stick a directional LED in, you lose a good proportion of that range, and the type approval no longer applies.Within the UK, the vehicle would still pass it's annual test, however in the case of an accident your insurance company would most likely void your policy as you've essentially modified the vehicle with a non-type approved part. The only way around it, is to fit a type approved LED lamp assembly, and notify your insurance you've modified your vehicle from standard (which will usually cost you in a premium increase).There are plenty people who do it and never bother notifying their insurance company, however all it takes is for an accident and the insurance assessor to query something, at which point they'll simply check with the manufacturer what was fitted to the vehicle when it left the factory, and if what's fitted doesn't match, then they'll void the policy along with any claim.If I was to do it, I'd simply fit them and see.As long as there's no bulb failure sensing, and the lights still have a physical fuse, most sidelights are simply controlled directly via the switch, or via an internal relay in the BCM (just because something is switched internally in a module, doesn't mean the powered circuit is being switched electronically).The chances of permanently damaging something are pretty slim, and provided you don't keep running them when you notice any issues, car modules are pretty robust.

author: amyk
author_rank: Super Contributor
timestamp: March 22, 2014, 01:05:51 pm
content: Reading about all the odd issues appearing in this thread makes me think that cars' electronics have become far more complex than they really need to be... a plausible scenario is that a bulb failure sensor is being confused by the much lower current draw of an LED and sending erratic signals to the ECU.You would need the schematics for your car to figure out the situation exactly.I drive a vehicle from the early 80s - and the ECU has nothing to do with the lighting on it. There's a current sensor for bulb failure but it's a simple, electromagnetic type and its output goes directly to the indicator on the dashboard.