Can you do voltage drop testing if the starter is not turning over (no crank)? When starting ignition (no crank) the voltage drop from (-) battery to starter housing is 78mv so good. My voltage drop from (+) battery to B-terminal jumps to OL. Its a new good starter. Starter relay is also good. The voltage drop from (+) battery to S lead is also OL when starting (no crank). ???
Greatly appreciated. Very well done video. Unfortunately this method will not work with newer Fords and their gateway modules, you need one of their expensive special break out boxes to test all can lines. that box is roughly $600-1000
How do you do the first test if your starter won't crank the engine at all Should a failed attempt aka just turning the keys still energize the circuit suitably for this test?
Bravo, excellent, intuitive description of the can bus function. I have such an issue, I have power at the DLC at pin 16, and good grounds at 4 & 6. But no communication with the PCM through my Scanner. All the fuses checked out good, and for good measure I replaced the PCM Relay in the Power Distribution box. According to the Wiring Diagram for my 98 F150, both the High Bus & Low Bus are located in the PCM. I didn't suspect the communication problem with the PCM because the Truck Runs. But now if I do the Ohms test, I might discover that one of those busses are bad. Recently I had an Alternator that went bad sending a surge through the electrical system, and blowing a 175 amp fuse, all of which I replaced.
What a very detailed video! Great job and thank you for taking the time to share it! I've watched several videos dealing with voltage drop, but by far, this one is the most detailed and comprehensive yet. Cheers
thanks! but on a 2013 forester the green plug is on the passenger side under glove box top left, i spotted the disconnected plug while working on other stuff and thought it came unplugged.. so i plugged it in and tucked it away. next thing you know its throwing 9 codes.. p0851 p0140 p2195 p2196 p2096 when it previously had none. now i know its suppose to be unplugged, thanks.
I have a 2003 DODGE CARAVAN SE V6 3.3L The minivan is giving me a P0300 code. I turned on the engine and left it idling. Connected a test light to a ground and connected a vacuum gauge to a vacuum port on the upper intake manifold. I did a cylinder drop test using the test light while removing one wire at a time from the coil pack and observing the vacuum gauge needle for movement. As i was removing one wire at a time from the coil pack using the test light the vacuum gauge needle was not moving so i can know which exact cylinder is misfiring. Do you happen to know why the vacuum gauge needle was not moving?
Good morning sir, i have a 2003 DODGE CARAVAN SE V6 3.3L, it's giving me code P0300, i did a cylinder drop test using a test light removing one wire at a time from the coil pack while the vehicle is parked and idling in a house garage, i can't tell which exact cylinder is misfiring, should i redo the cylinder drop test using the test light while doing a brake torque test and removing one wire at a time to see if i can tell which exact cylinder is misfiring?
I SEE NOW CLEARLY ,,,,,,,,,,,,,,,, SNAP-ON SCOPES ARE NOWHERE AS GOOD AS PICO . CAN'T WAIT FOR THE NEW HAND HELD TWO CHANNEL PICO TO HIT THE MARKET !!!!!!!!
Great informative video. what speed did you have you oscope set at to get that waveform, and where would you start to look if the voltages were low on the busses?
In most vehicles today, the car will start without a CKP. The PCM will reference the CMP to synchronize fuel delivery, but it will take a long crank before it starts.
With snap on scopes you need to zoom way in in order to increase the sample rate then you can pause it and zoom out to see the details of your CMP/CKP . There’s a term with oscilloscopes called “aliasing” and it happens when you zoom out to a slower time base and there isn’t enough sample points to capture the details of the signal. Snap on scopes have a comparatively lower sample rate so in order to get the most detail you have to zoom to lets say a 20mS sweep to get a good view of the CPK sensor . Then you would stop the recording and zoom out to get your CMP sensors and and CPK in a view that you’re ok with to verify their synchronization.
Good comment sir. Question in your personal opinion wich osiloscope is better pico or snap on I just trying to see so I can decide I don’t know anything about osiloscope but i heard osiloscope are good tool . Thanks
Excellent tutorial. I'm a DIY guy. This complete explanation from the wiring diagram to the testing procedure is very helpful. I was able to follow the process and understand it completely.
Enjoy your weekend with all your family around you, MR DIAGNOSTECH Take care 👍 WHIP SMART,MR DIAGNOSTECH from Nick Ayivor from London England UK 🇬🇧 ⏰️ 11:01AM Good Morning
Now I wish you made a video about how the solenoid itself works when you get a failure on that side of the runner. I have one that is pulsing 12 volts on ground and says the circuit is high but no resistance to the ECM
EXCELLENT Voltage Drop Testing method...Your only MAJOR Fault is that you didn't tell the Public where both ends of the Green Jumper wire were connecting too to partially Crank the Engine.
