today i'm going to show you a really important
skill you can learn about fixing cars what do you do if you have a trouble
code say for the engine coolant temperature sensor you
replace the sensor but the code comes back and it's not fixed
you scratch your head do you run away to a mechanic and pay a fortune
no you can actually fix it yourself being a mechanical last 52 years
i see lots of that customer tried to fix their own car
cooling temperature sensor maybe an oxygen sensor
maybe a mass air flow sensor they get a code for it they replace the part
and voila the check engine light comes back on with the same code
now for my first warning here if you're ever fixing your own car you get a code
and you replace a part if it's a sensor like a maf sensor oxygen sensor please
only use the oem the original equipment manufacturer
sensor now you don't have to go to the dealer and buy it let's say
it's a lexus or a toyota it's got a nippon denso sensor
you can buy nip and denso sensors lots of places but don't
say it's got a denso sensor don't buy an aftermarket bosch sensor a
lot of times they won't work and please don't buy any of those really
cheap chinese sensors i have had numerous customers over the
years go and buy especially a maf sensor a mass airflow sensor
from a discount auto parts store it's made in china they put it on their car
but the code comes back and i find out it's just because they bought
a bad sensor always buy the oem factory sensors
the company that makes them they're very specific but let's say you did buy the
factory oem sensor you put it on you reset the trouble code say erase
code just yes and then you drive around the stupid
check engine light comes back on with the same code what do you do well
here's what you do if you got this code the po117 for the engine coolant
temperature sensor isn't working right so you find where
the sensor is in this case it's right here you can always look it up online i
use all data for this stuff the sensor is right
here the wire feeds it so you just unbolt it put a new sensor in but
if the code comes back guess what that didn't fix the problem
what are you going to do scratch your head give up start screaming and yelling
no you can use this tool this is an otc vet 100.
what it does is it generates electricity all you have to do
is hook it up to the battery positive positive negative to negative
the green light comes on so you know it's right it's not green it's not
hooked up right so you know if it's got power
then as you can see it's got the input power and the output
now the output is adjustable now it shows the input and the output now it
starts at half a volt but we're going to put it
on 5 volts that will be the output that comes out that we can probe
now why or why are we putting it on 5 volts well
that's because the engine coolant temperature sensor
it's a 5 volt reference sensor it uses 5 volts it doesn't use 12 it's a
computer sensor so whatever sensor you're working on you gotta find out
what voltage it is i use all data information systems they give great
information you of course can use google whatever
find the voltage of the sensor you're working on you set that at that voltage
then we're gonna use the scan tool you can use any scan tool that does
readings of the various sensors they all don't make happy noises like this bosch
but then we'll select coolant which will
give us the raw data coming from the coolant sensor now here comes the tricky
part when you disconnect the connector one is
five volts and one is ground you want to give power to the five volt ones but you
don't want to ruin the system so you can do like i do and look it up
on your all data but if you don't have an information system just get a
voltmeter so with the key on touch one side then
the other well that one's ground it's zero volts
as you can see and the other one is 4.9 volts so that's the 5 volt one
the one on the left side and as you can see the one on the left side
that is a green with a black stripe on it there now you can see the
green with the black that's the power one so you just connect it back
on down with the little setting unit set at five volts take off the little tip
guider because it's sharp and probe it into the green and black
wire that sends power you just probe it in then once probed
you push this button here that sends the five volts through and
you read the data if you're adding five volts and you look at
the data on the scan tool and it says five volts and you got the
code on that means the sensor is bad that means you bought the wrong sensor
or if you're just testing it and you didn't buy one yet you know it's
time to buy a new sensor but if the voltage is
lower than 5 volts that means that either the wiring
from the computer to the sensor is bad or the computer itself is bad
and in this case it's 3.5 volts so either the wiring
or the computer is bad you want to pray it's not the computer now of course
you don't want to guess with an expensive new computer and this lexus
parts labor reprogram's going to cost you well over
a thousand dollars so here's how you test that what you do is
you go to the computer itself and if you're going this far you
definitely need something like all data as you can see here that's all the
computer connectors and it shows you what each one is
you got to go through them all find out which color wires and which one is the
one for your temperature sensor then you go
to that wire and you back probe that connector and give it the five volts
so of course you need to know where the computer is well in this case it's up in
the dash you got to pull the glove box off and i'm not going to show you it
because the only reason this one came out is
because i unplugged it to make the code pop
there's actually nothing wrong with this it's a lexus it doesn't matter that it's
19 years old i have never ever had a problem with the
ect sensor on any lexuses but i'm using it as an example so once
you find the computer and the feed wire you plug this in and
give it five volts and here's what you're looking for he gave it five volts
if the voltage reading on the computer reads the same
5 volts that means that the wiring harness is bad
that's what you're going to pray for you're going to pray
that it's the wiring harness in this case technically it was the wiring
harness because i unplugged it to make the trip code but if there was a
shortened wiring harness it would then read 5 volts when you gave
it power at the computer if the voltage on your scan tool
says a lot less than 5 volts that means that your
ecm is in process seeing the system right
and it's going to need replacing it gets expensive
probably that doesn't happen to you but again i've only ever changed one
computer on a lexus and it was a v8 400 model that was very
old it's a rarity that they go out in these
things unless the cars is wrecked and then all bets are off because wires
can short out and ruin everything big reason not to buy a wreck lexus
now you might think why would your car get weird because the coolant
temperature sensor goes out well that's because cars aren't as simple as
they used to be when i was a young mechanic
the only thing the coolant temperature sensor did was send data to your
temperature gauge so you could see if your car was running hot or not but of
course modern cars it tells the computer the operating
temperature it allows it to go into closed loop
operation so the oxygen sensors make it work efficiently and that doesn't
pollute it'll even affect how your transmission
shifts on a late model car so if that engine coolant temperature
sensor or ect sensor goes bad you could have all kinds of problems now
you know how to test them and this isn't a one-off fix
you can use this machine and a scan tool to test
any sensor you just need to know the voltage that the sensor operates on
many computer sensors operate on five volts but some are a little different
so you do have to research what exactly does it use for its power
supply well when you consider that this little tool
can let you figure out whether you need a computer or not
and you're not guessing it's worth its weight in gold because you don't want to
ruin any computer systems using 12 volts your battery of course is
12 volts this turns to 12 volts into whatever voltage you need do not
ever test a car using straight 12 volt power for example this auto
electric testing device and measurer it's great for measuring stuff but look
what happens when you push the button it supplies 12 volts and if you supply
12 volts to a 5 volt or a 3 volt system
it'll destroy it that's where this comes in really handy
gives the voltage you want and it only gives the voltage when you
push the button and the arrows turn on so if your car's
check engine light comes on and you change the part that it refers to when
it doesn't fix it now you know what you can actually do
about it yourself and considering that many mechanics now
charge 130 dollars and more an hour labor you might start getting into
this electronic stuff and if you're really good at it
hey maybe you'll end up like me and you'll fix them for a living but even if
not you can save yourself a ton safely
using the right voltage when you're testing stuff
so if you never want to miss another one of my new car repair videos
remember to ring that bell