Sensor grounds and the 5v reference circuit (a 2016 ScannerDanner Premium video)

I I'm really not sure why I took this job this is a 1992 Ford Taurus and somebody's been playing around with this this is actually my friend Pete his younger brothers neighbors car so it's one of those and apparently it has been to multiple different places and they can't fix it it's a no start there is evidence that someone's been tampering with just about everything so let me get you a couple of shots of what I noticed so far so what I typically do before I turn the camera on is I make sure that I have a fully charged battery when it comes to a no start diagnosis and that way I you know push the car down to the garage put a charger on it or grab a jump pack whatever just to get prepared and one of the things I noticed when I turn the key on as you can see is my tech engine light is not lighting so that's a good indication that the computer is not alive and talking and then of course we have other evidence which is we have an engine computer sitting on the passenger floor so what I was going to do is crank it over and watch the check engine light another tip on Ford systems would be if you turn the key on and the check engine light lights and you crank it over and the light goes out while you're cranking that means the computer is receiving an RPM signal that is unique to Ford but it is a good tip in this case I can't do any of that something else I noticed the fuse box is down fuses are on the floor again someone's been playing and so I opened the hood and of course the hood doesn't stay open I gotta get my vise grips to put on the hood shocks to keep it open no big deal hold car you'll have that but what I notice under the hood is more evidence of tampering injectors on plugs and then of course the engine computer itself you see this harness right here is unplugged so the computer that's on the floor inside the car yeah that's the computer for this car so of course the check engine lights not going to light when you turn the key on when the computers not even plugged in I'm seriously concerned about this vehicle and I'm concerned because when people get in to a car like this and start playing around it makes my job so much more difficult so first thing I'm going to do is put the computer back in and start from scratch see what we're missing all right what else is unplugged plug this fuel injector back in looks like the ignition coil is new not sure about the plug wires or what's inside looks like maybe the module has been replaced although not recently it is a different color different color meaning it looks like it's been changed at one point well let's go back inside see if we can do that check engine light test turning the key on still no check engine light okay so we have evidence of a computer that is not what I say alive meaning missing a power missing a ground maybe a shorted reference going back under the hood now and we're going to do some quick 5 volt reference circuit checks memories coming back to me on this 92 Ford and I remember the computer grounds they had issues with this computer connection in this location I might have to unbolt this for you guys to see it I don't want to move things yet just in case I accidentally fix it but just keep that in mind computer grounds in this location we're known for issues so the checksum I'm doing that I mentioned inside the car is on the 5 volt reference circuit the 5 volt reference is a just think of it as the computers blood or cardiovascular system that that 5 volt reference is really the lifeline of this entire system when it comes to testing the 5 volt reference circuit what you want to do is find a sensor that's easy to get to the TPS which is right here in this location is my best sensor on this car to check this reference circuit we could also go after a pressure sensor for the EGR system and it's right here a little bit more difficult to get to though because it's underneath the connector and we can also check the intake air temp sensor which is right here but when you check thermistors which is what this is called you need to unplug the sensor to check for the 5 volt reference in our case the TPS is going to be the easiest place to do these checks so I'll walk you through that right now starting at the top wire on this sensor just using a back probing tool I actually got these as part of my kit my picot kit but they work well with just about everything all right so right away we have really good direction as far as where we're going with this car you can see that we're showing eleven point four volts on the top wire of this TPS and guys let me tell you this is a sensor that should never have battery voltage on some of the older systems older being maybe in the 80s and some of the Euro and asian cars not our domestics here in the US would use a throttle position switch that actually did have battery voltage on either one or two of the throttle position sensor wires now that particular sensor was called a throttle position switch it was exactly that a switch contact not a potentiometer like this one is so sorry for rambling there this potentiometer should never have battery voltage okay so right away we have a reference circuit problem guys please pay attention to the description of this video I will put links to other videos I've done that deal with the 5 volt reference circuit and it will give you a real good idea of what I'm talking about I'll also include a playlist to my 5 volt reference chapter in my book so what I've done is I've taken the segment's in my book and whenever I have videos like this one that relate to a chapter I'll make a playlist for that so you guys that have my book you can follow along in the chapter and you can also follow that playlist again that'll be in the description of this video so let's do the rest of the wires now on the TPS see what we have so this one's eleven point four eleven point four one the next one down same thing and one more I think this is gonna tell me a lot I expect to see high voltage here - this is my sensor ground and I do not so if you remember when I started I talked about those computer grounds by the battery and as I was going here that's what I was thinking of but this sensor ground which is that nope there it was right there now am I on the sensor ground this 11 - or am I not getting mighty pinon straight and I'm hitting the signal wire I have to be sure what I'm doing here because this is a critical critical test as far as direction and where we're going let's make sure we're getting on that ground pin I am poking a small hole in this wire because I am Not sure yep all right that's the ground wire itself reading eleven point two volts it's a little bit different voltage reading than the signal and the reference let's try to get this in there this T pins a little bit or this back probing pin is a little bit short for this connector there it is right there okay so what this means is we have a bad computer ground it could be a sensor ground circuit - but the way that these sensor grounds work us is all of the sensors lots of Sun in this picture hopefully this shots still okay I just wanted to get you a little bit more zoomed out view of all the sensors under the hood so the mass airflow the PFE sensor for the EGR or the intake air the TPS the engine coolant temp sensor which is down low you can't see all of these sensors I mentioned mass airflow all of these sensors share a ground circuit that go back to the computer and then the computer takes those grounds and grounds them externally so I'm gonna keep you guys focused on this eleven point two volt TPS ground while I'm wiggling the connections under here the computer ground connections let's see what we get just watch the I'm worried about the computer grounds do you see that man that's cool hold on one second let me move this out of the way lots of shadows here that Sun is not helping this camera right now hope these shots turn out okay I'm pretty sure the last shot you guys saw the the ground voltage change that's pretty cool and what's really cool is just experiences is key I'm thinking about a car you know it's probably been 10 15 years since I've worked on one like this [Music] with the computer ground issue but these are things you never forget you know you get a car that that beats you up talked about this a lot in class that you get a car that beats you up and you might let it get to you even but if you are diligent and you find the problem and you don't give up you will make money on that car for 20 more years not that particular car but that design that system you never forget the connection I'm messing with Gus watch the multimeter is this one right here and back in the day we used to take this connector and we would cut it and hardwire this now why they put a plug in style connector that went to the battery I don't know but watch my ground voltage on my TPS when I wiggle this connector watch oh you know what they're right there actually what I'm doing that I can hear the fuel pump running too and I didn't notice this till now but look wires broken and this one the one that's still connected watch the what's the voltage that's pretty cool okay so we're gonna fix this real easy I'll show you how to do it I need shadows horrible try to keep my my body out of this shot alright just gonna take this connector we're just gonna get rid of it completely look at that broke on the other side just pulling on that there are three grounds let's cut the ends of these off corroded these wires are bad look at the powder like the residue coming out of there you know if the camera picked that up I'm not pulling this harness part it really needs to have the wires cut down further I'll probably have Danny do that like I said this is one of those friend ones so I'm just gonna get this thing working for now okay I'm hoping I apologized for the Sun here up I'm hoping if I keep my shadow in this shot that you guys will be able to see what I'm doing better we'll see I'm hoping hoping but look at this wire how corroded that is you know what happens is that end up down into the harness that can go that can go two feet down into that harness see the spark that was just current flow from the key still being on and the computer waking up that wouldn't be a danger if that touches ground that's what we're going to do with this circuit so you see that again what that's just the fuel pump turning on okay yeah these connectors bad alright so what I want is I want this car to run I was going to use my my heat-shrink style butt connectors but I'm not wasting them on this because this is really needs to be redone so I'm just using a barrel connector we'll put two of these together again what needs to be done to fix this properly and my guess is they probably won't that harness right here this needs to be stripped down further we might have to go maybe a foot into that harness and cut out the bad wire when you see copper wire that's that's corroded like that it has some black in it and it has a different color copper it's oxidized very bad now this will work for a while but that would be the right fix to get rid of the bad wire I'm not doing that in this scenario basically on a freebie I'm gonna fix this and tell him what to do and he can handle it I just want to hear this car run that is my focus right now and I want you guys to watch my multimeter as I get this together when you have wire like this it doesn't dumb it doesn't solder either solder won't stick to it so it's the other reason we want to use a butt connect you all right you guys conceived it my voltage dropped down to five now that could be I could have been wrong that bottom wire might not be my sensor ground that actually might be the reference circuit well we'll see I'm just thinking one of two things either when I connect this second ground that drops to zero near zero and if it doesn't then the wire that I'm actually on right now is my reference in my top wire or middle wire was my ground I don't let's see let's just touch it okay and I was wrong that bottom wire is my five volt reference and my top wire then or middle wire probably top wire would have been the sensor ground the one that was reading eleven point four but you can see this is a good example though I was again wrong about the connection on the TPS on which wire was which you can see how valuable the five volt reference test is in our case having 11 volts on the five volt reference circuit that screams bad ground in fact every time I've seen it it's been a bad ground let me show you the top wire so while I have this opportunity let me move back up top that should be my sensor ground wire the top it's gray and red if I take this off I'm not making contact let's get back on that this pins a little bit short for this connector all right 11:31 the keys been on for a little bit so watch that top wire that should be my here you guys are not seeing me move that I just moved the connection to the top wire on the TPS we're reading 11.3 on the meter I connect this ground watch it this should be a sensor ground sensor ground wires what you want to see is less than 0.1 of a volt with the key on and there it is right there so bad sensor bad not just sensor ground in this case I'm measuring sensor ground bad computer ground which was raising voltage on everything including my 5 volt reference circuit let me move that back down to the 5 volt reference wire I'll take the ground back off ok this is a also a good lesson on ground to ground voltage drop testing and you know it's kind of strange that my meter is connected to battery ground over here and my other lead my yellow lead is going to the sensor ground and I'm reading voltage and the cool thing about that is the more you see bad grounds when you do ground to ground voltage drop tests the more it makes sense you don't need an ohm meter volt meter is the way to go pretty cool alright moving this back down to my 5 volt reference eing this but I'm doing the same thing I did before just back priming the TPS connector 11:39 connect up this computer ground which again the computer ground grounds the entire computer board all of the sensor grounds go back to the computer board so we're grounding the sensors to when we do this and there is my normal 5 volt reference circuit voltage let's crimp that so imagine this car and the guys that were working on this they were all over the place they were putting in ignition coils unplugging injectors unplugging the computer I just wonder how many hours that they had into this and this wasn't Pete's brother this was wherever Pete's brother took her Pete's brothers neighbor took the car I guess they had it at some garage and to be fair to Danny which is Pete's brother's name he doesn't do this stuff and so I'm not knocking him in fact I'm not knocking the neighbor either I'm just making a point that how many hours that you would have in a repair like this or in a troubleshooting procedure like this when guys we had this we had this narrowed down very very quickly just knowing principles okay and again for you guys that are new at this the playlist that I'll put in the description of this video the 5 volt reference circuit I have so many case studies that you guys can watch that will benefit from this and it will give you really really good insight into what I'm doing and how to use this in the future so again this would have been better done using heat-shrink style butt connectors but after cutting out the bad and corroded wires this is good enough for now I'll let Danny know about it I'm hoping this car starts and runs I honestly don't expect it to run very well because somebody was in here playing around but I don't know let's just see what happens we'll go from there if it still has a running problem once it's running we'll address that as well but this car should start and run at this point nice shadows sorry guys I'm gonna try to start it look my check engine light is on - real quick notice check engine light is now lit alright cranking it pretty cool car is running which is what I cared about awesome the Sun is killing me on these shots well not so bad guys the takeaway from this is to know your fundamentals and if you understand the five volt reference circuit you can quickly identify problems like this I've done this many many times the last one was actually on a Honda that had the exact same scenario the only difference was I was reading 9 volts on the 5 volt reference circuit instead of 11 like we had on this car and it ended up having a bad block round so again description to this video I'll put some other relevant videos for you guys to watch to get you up to speed and I guess the other thing is don't be afraid when you see a car that's been messed around with sometimes it goes pretty smoothly in this case it did but sometimes they can be a nightmare too but again knowing an approach having an approach having good direction that's what this is about know your systems keep following me guys I'll teach you that a lot of you already know that thanks for joining me I'll catch you next time

Channel: ScannerDanner

Views: 210,067

Rating: 4.9224777 out of 5

Keywords: engine performance diagnostics, technician training, auto technician training, rosedale tech, auto repair, ASE L1, how-to, DIY auto repair, no start, no fuel pressure, no spark, no check engine light, no communication, Ford, bad ground, sensor ground, 5v reference

Id: 1Nvyc_88AbY

Length: 27min 48sec (1668 seconds)

Published: Mon Oct 29 2018