Did the Dealership diagnose this car right?

[Music] hi everybody and welcome back to a new episode of diagnose Dan today we were working on a 2003 Oda for and the customer complained is the ABS light is on the car has been to another shop they cleared the codes the ABS light went out but after a while it came back on it has also been to a Ali dealership and they told them it needed a new ABS control unit now since the new ABS control unit is really expensive from Audi they asked me for a second opinion so let's see if we can find out what the problem is with this vehicle and with your help I don't think it's going to be a problem so let's diagnose this together [Music] this is the car we're working on it's an s4 so this one has got the big v8 and this one has got all-wheel drive and the next step we're going to confirm the customer complain and we're gonna scan for codes now a lot of cars think that this cantle is gonna tell me exactly what part I need to change on this car now this is not true scanning the car for codes is only the first step in a diagnostic process and it will tell you what to check next another myth is that a aftermarket scan tool will give you different codes than a factory scan tool this is also not true it's the car giving you the codes and the scanner is only a way of communicating with the car so the scan tool is not making the codes up it's the car giving the scan to the codes let's confirm the complaint let's turn the ignition on and ABS light comes on and goes out again so the customer already told me default was intermittent so let's hook up a scan to and see if there are any fault codes stored in the ABS unit let's select ABS and let's read the dtc s now if there are any fault codes stored in this ABS unit it's gonna be history codes because if the code was present right now that light would not go out right now if there are history codes stored in the ABS unit at least we know what caused the light to come on when the customer was experiencing the complaint and we've got a fault code stored that is the O one 435 brake pressure sensor one voltage supply now just imagine for a minute were one of the people believing that the scan tool is telling us exactly what to change on that car in that case we just need to find that pressure sensor swap it out for a new one in the cars fixed right well it might turn out that this car indeed needs a pressure sensor but what have we changed it out in the cars and Fix is a customer gonna tell you well that can happen here's your money and try again no that's not the way it works I mean it's called Diagnostics you can't just drive by a shop let them pull coats and tell you what's wrong with your car it doesn't work that way if you don't go to your doctor and say hey doc I feel like I'm gonna faint he's not gonna tell you well I had a car a guy in here a car a guy in here yesterday with exactly the same symptoms he had high blood pressure just take some pills and you're fine it doesn't work that way he needs to measure your blood pressure take a look at your heart find out what's wrong it's like detective work and it's the same with cars on this ABS unit the pressure sensor is mounted on the outside of the hydraulic unit on a lot of newer cars the pressure sensor is built into the hydraulic unit itself and it's non serviceable now this one can be replaced it's a three wire sensor and what this sensor does is what's the hydraulic pressure within the ABS system for instance when you push the brake pedal and the computer can see this because it's watching the brake pedal switch it's expecting the hydraulic pressure to arise right now if you're braking but the pressure isn't rising there must be a leak or something must be wrong with the system and it will flag a fault code so actually this is a very important sensor the computer flag the code for this pressure sensor so we need to check it out just like the doctor who's taking your blood pressure we need to take a closer look to our patient now it looks like a patient is doing just fine right now the symptoms are gone the light is out so I'm not expecting to find anything wrong with it right now since it's the only lead we've got we've got to check it out now in order to do some measurements we need to know what to expect on each of those three wires so let's take a look at a wiring diagram so let's take a look at our outtie wiring diagram this module over here is our ABS control module and this be 107 over here is going to be our hydraulic pressure sensor now as you can see this is a three wire sensor we've got a red and white wire a yellow and green wire and a yellow and black wire now how do we know what to expect on each of those wires that's very simple just go and stand on the component and click on the little multimeter now I'm sorry this is in Dutch but I've got the Dutch version over here we can see if we measure from pin 25 to battery negative with the ignition on we're supposed to measure zero volts this means that pin 25 the yellow and black wire is going to be our ground wire we measure from pin 42 to battery negative with the ignition on we're supposed to measure 5 volts this means pin 42 or a red and white wire is going to be our power feed if we measure from pin 26 to better e negative and we're not pressing the pedal we're supposed to see something about point four of a volt and when we do press the pedal we're supposed to see something from 0.4 volts to two and a half volts this means that pin 26 or our yellow and green wire is going to be our signal wire in order to do some measurements we need to create some space now in order to do that we need to get this kiln the reservoir out of the way now already got the screw wrap because I showed you the sensor just a minute ago but what I want to show you guys is that I use these elastic bands with hooks on them to get components out of the way now these are really cheap I found like five and they come in different sizes for two euros now the great thing about these is when you're hanging calipers for instance and you've got one of those metal s hooks you're quite limited to where to hukum to because the S hooks aren't stretchable these are stretchable so it's always easy to find a spot to hook them to and since they're elastic they're quite forgiving on the material so when you lean on it it won't immediately break in the wiring diagram we've seen the red and white wire is the power feed and in this case it's five volts the yellow and green is the signal wire in the yellow and black is our ground now you can measure this with a normal multimeter and I'm using my scope as a normal multimeter these are slow signals so you don't really need a scope let's set it up as a multimeter and we're expecting to see five volts so I will set it to a 10 volt range now let's back probe the red and white wire which is supposed to be the power feed and turn on the ignition and as you can see five volts so that's fine now let's measure the signal wire and let's scale it down to five volts and the signal should change as I press the brake pedal because the hydraulic pressure inside the hydraulic unit will change so let's press the big brake pedal and I don't know if you guys can see that but that signal change now the less thing we need to check is the ground now you might be thinking is it really necessary to check that ground we saw the signal change so obviously the sensor is working so we've got a ground well you are right we've got a ground but we don't know if that ground is any good if we've got a poor ground connection this could have an influence on the level of our signal voltage so yes it's very important to check that ground now the best way to test the ground is using a test light if the ground is good enough to light a test light it's certainly good enough for our sensor so let's back probe the ground wire let's hook our test light up to battery positive and when I touch the ground our test light should light up so let's check our ground wire and it lights up so our ground wire is perfect now as soon as we are using the test light let's also use the test light to test the power feed to the sensor now since the power feed is only 5 fold I'm expecting the test light to light up very dim so let's back probe the power wire let's hook it up to battery negative oops and let's see if our test light lights up let's turn on the ignition and I don't know if you guys can see that because it's quite dim but the test light does light up so far we've only been measuring on the sensor itself we don't actually know if the signal makes it into the computer now an easy way to check that is select the data pit of the pressure sensor on our scan tool and see if the value changes as we press the brake pedal now let's select a brake pressure data pit let's see here it is brake pressure let's select it and let's turn it into a graph so it's easier for you guys to see now what I'm gonna do is sit inside the car and press the brake pedal and remember this is processed data so if the signal is making it into the computer you will see this graph chains so I'm going to see it inside the car right now and pressing the brake pedal and releasing and pressing again and releasing we've checked the power we've checked the ground we've checked the signal wire and we even saw the signal made it all the way into the computer looking at the break pressure data paid on our scan tool now we already invested a lot of time in this car all the tests are fine the car is not acting up and basically we're getting nowhere so let's send this customer on its way and let them come back when the car is acting up now the downside of thinking like this is the customer is probably not willing to pay for an answer like I don't know what's wrong with your car so all the time we've invested this far is wasted now this is a problem with intermittent faults shops are losing money that's what nobody likes them now but why would they probably intermittent why would something be fine right now and act up 10 minutes later or an hour later something must have changed now these cars are exposed to the elements they're supposed to heat cold vibration water now to some extent we can recreate these circumstances we can do a tap test we can wiggle wires we can heat things up cool them down now to make a long story short and not to turn this into an hour-long video I want to show you what I've found using a heat gun and a product called freezer it's a shop froster which can cool things down very fast it's giveaway time in the next step we're picking a random comment from my last video if your name shows up in the screen please contact me my email address is in the description box of this video and we'll make sure this fantastic ODIs impro sensor simulator is coming your way we're also doing a new giveaway we're giving away this fantastic battery tester all you have to do is follow a link in the description box of this video answer a question and you're in on the giveaway [Music] off-camera I did a lot of testing I've kept modules I've tapped the sensor I heat things up I wiggled wires cool them down just until I found a problem right now the test light is connected to battery positive the other side of the test light is connected to the ground wire of our pressure sensor now as long there is a ground on it's pressure sensor the light is lighting up now you guys watch that test light as I heat up and cool down the ABS unit now to make sure it's not a coincidence I heat it up and cool it down a couple of times in this test I'm using a product called freezer now you don't need this you can also use shop air but that would be very noisy on camera so you guys watch the test light [Applause] [Music] [Applause] [Applause] [Applause] [Applause] as you could see when we heated up the ABS control unit we lost the ground to our sensor now when we lose the ground to that sensor that sensor stops working and when the sensor stops working the computer is gonna flag a go for it now as we can see in the wiring diagram that sensor grant is coming directly from the ABS control module I'm suspecting there is a bad solder joint on the circuit board of that module and keep in mind that things expand and retract when they're heated up and cooled down again so when you have a broken wire a bad connection or a bad solder joint you might have continuity one time but lose continuity the other time depending on the temperature now that ABS module is placed right beside that big v8 so when you're driving around with the hood closed it could get really hot under the hood and that's why this problem was intermittent this car was diagnosed by the dealership with having a bad ABS control unit now I agree we're losing the sensor ground because of a bad ABS control unit now there are three ways we can fix this car number one we can replace the ABS unit with a brand new one from Audi that's gonna cost about 1500 euros option number two we can get this unit fixed we can get it remand for a couple of hundred option number three we can solder in an external ground to our sensor that's kind of cost us about 50 minutes now for now we're kind of solder in the dwyer and afterwards I will talk to the customer and see what he wants now I can kind of guess which option is gonna choose so I'm quite curious what would you choose so please leave a comment in the comment box of this video what will you do option 1 2 or 3 [Music] [Music] [Applause] [Music] [Music] [Music] [Music] [Music] [Music] so we sold it in a new ground wire and attached it to the valve block itself which is never gonna lose its ground so this is a good ground I'm very curious if this was your car would you go for option one which is 59 euros option to a couple of hundred euros or would you say well this only took you five 50 minutes is a good repair leave it like this I'm very curious because technically there's nothing wrong with this ground it's a solid ground it might just not look as pretty so leave a comment in the description box I talked to the customer and I gave him three options replacing the unit with new one getting this one repaired or leaving the repair as it is now to no surprise the customer chose the last option I mean this is an all the car and that repair is gonna last the rest of the cars lifetime now I hope you learn something about intermittent problems they can be a little bit tricky and they need some detective work now if you want to learn more please subscribe to my channel when you hit a little bell you will get a notification each time I post a new video and remember diagnose then fix it again see you next time guys somehow at the feeling this video wasn't finished so this is a little bit of bonus footage if you've been watching closely you saw we had a fault code for losing a power supply now in the end it turned out that we had a ground problem you might wonder why now this is because of circuit design some circuits can tell the difference between losing a power or ground especially on all the cars so if you have a power supply problem make sure you both check the powers and the grounds now I told you guys I fixed a car but I've never proved it to you so we're gonna do one more cool test we're gonna take a look at our test light again and as long as our test light is lit we've got a good ground I'm gonna heat up the module until the point using our ground at the same time we're gonna take a look at our pressure data pit on the scan tool now when we're losing our ground I'm gonna attach that sold it in ground wire to the exact same spot we're gonna fix it permanently now if our values return to the same values we had before the ground dropped out we know we fixed the car [Music] [Applause] [Music] and if your name shows up on the screen please contact me my email the resignation of this rigid [Music]

Channel: DiagnoseDan

Views: 266,516

Rating: 4.9540634 out of 5

Keywords: Skotty Kilmer, scannerdanner, South main auto, pine hollow auto diagnostics, Audi, abs, fix, Diagnosedan, diagnose, diagnostics, repair, educational, faultcode

Id: RW8u3mngeD0

Length: 27min 21sec (1641 seconds)

Published: Wed Nov 20 2019