Pressure Sensor or Potentiometer Signal Fixed at 0v [Circuit Integrity Testing] 

I think people should buy Mr Paul's book as a appreciation for offering invaluable free knowledge and also to encourage him to make more videos.

Wow! I wasn't expecting anything like this video turned out to be. I feel like I just subscribed to a class and I'm about to be a certified home technician. Good stuff! Very impressed with your work and when you through it on the white board, I was blown away! Keep up the great content! Thank you for your time

OUTSTANDING!!! I personally appreciated the professional approach and clear explanation of the electrical issues a automobile might have. Great learnig.experience. THANK YOU.

Hello Just wanted to say that i am blessed to see any of your videos!! You made a huge impact on me and gave me knowledge that most people will not do!!!! Thank you so much sir!!!!

KNOWLEDGEABLE Sir ScannerDanner Thank you 👍 Take care Sir ScannerDanner From Nick Ayivor from London England UK 🇬🇧

Thank you very much. It is hard to ignore the negatives. I just need to remember that I don't need to always defend myself. I have always let me work speak for me. It was really cool of you to defend me over there. I truly am grateful.

As an instructor your a natural communicator. The information you provide is priceless. I do wonder if your students absorb the info considering all the variables to every circuit design by manufacturer. I wonder if its possible to be a general service technician at all or do we train techs to specialize entirely on the electrical diagnostic side of the business only and some on the mechanical side of the business.

That is a great question! One way is to look at some of the other sensors wire colors. Grounds are typically shared between sensors. Also if I see a 5-0-0 sensor I will jump the ref. to the signal using a 5kohm resistor and watch scan data signal for 5 volts. If you use the resistor and jump the ground by mistake = no harm, no foul. DO NOT do this without a resistor if you don't know which is which

This is a great Video, I will be happy to have an instructor like you you all day long. Thank you Sir.

Thank you very much for this video, man. I have difficulties understanding lessons but you made it very clear for me to understand, a little quick here and there but great work non the less! My 2001 Z28 Camaro has a P0452 Engine light and I will test it tomorrow to confirm it's a sensor, thank you very much once again for the video!

it sounds like someone is snoring in the background! Pay Attention kid your getting taught by one of the best!!

didn't have chalk boards like that in my school. great vid

I was also wondering about the question below (everxxxx), about possibly jumping the 5v ref to a shorted signal wire and causing damage. Would also like to recommend Paul's book, explains things well and if you're still not sure about something he always responds to emails to your questions. Top guy!

Just simply amazing. Great job.

@Bonfield2002 Thank you very much for the compliment. I always tell my students that it will take years to absorb all of the info I pound into them with my class. This is why I created this "field manual" (my book) for them to take with them in the field. It is the one book they will want to keep in their toolbox!

Hi Paul I am fairly new to troubleshooting cars.I just watched the video that you and Eric did on misfire.It was awesome as usual. Some of the comments are proof that how many people do not appreciate your level of skills and understanding of Automotive electronic and computer diagnostic.I mean try to explain what an ATTENUATOR is to Joe the muffler man .Please ignore the negatives an focus on positives which are way more as I read. Keep on the fabulous job that you are doing.Thank you

Thank you very much for this very detailed video! It helped me understand why I have voltage on the signal leg of my VPS with sensor unplugged.

Thank you! Great video it helped solve my issue with emission monitors not being ready. The aftermarket fuel pump had the 5V Ref and PCM signals swapped at pigtail. After I swapped the pins on 8 pin connector I got 2.7 V where before I was getting 4.07. I wonder how many fuel pumps were delivered with that quality issue. Thanks to this video I was able to get 2002 Mustang to pass CA smog.👍🏽👍🏽

Great explanation. Thank you.

Respect! And knowledge! Thanks✌️

The previous post, I accidentally wrote batterias. I hit send before I was completed with my response. Sorry about that. By the way great videos with a lot of very useful information. Thanks

This is great, I've been fighting a P0451 & intermittent P0452 codes on my Escape. I'm going to do this test tonight to confirm my sensor is good or not. I'm a subscriber after this video!

Very informative video. thank you

You are amazing and great teacher

Parabéns meu amigo, sua explicação é impressionante!

NOT ONE TAKES ABOUT, Other Reasons Why You Get Po452 code. I have a 2004 Silverado that sat for along time. I removed the fuel pump assembly, empty the tank, wipe clean and reinstalled all. Tried to start engine, it would crank, but hot start. Sprayed starter fuel into intake and it would start then die when starter fuel ran out. When to Auto Zone and paid $140 (Refundable if returned in 90 days) and found I had a P0452 code. I kept thinking it had to do with the opening of the fuel tank. Finely (After watching hours of videos) decided to remove fuel pump system. Cleaned opening and o-ring making sure o-ring was in the slot. After installing fuel system, noticed o-ring had come out, moved back into the groove, installed ring, and all connectors. After cranking 2 times, fired right up. All side remember hearing that if the gas cap was not tight or was leaking can cause the same problem. I wanted to pass along since I did not find a single video taking about the solution of a lose of pressure or a failed gas cap under P0452 code.

Very helpful. Thanks!

You are correct my friend. This is why I did another video. I called it "Signal Circuit Integrity Testing Update for my eBook" Also Section 10 in my eBook "Signal Circuit Integrity Testing" I have addressed this issue. Thanks!

Hi and I’d like to thank you for this video, awesome explanation keep doing your great job great for you!!!!

thank you!

All I can say is, "Thank You" Oh, one more thing... Genius!!!

You are very welcome my friend.

@ronlyon77 Thanks for the comment about the book! Read below about the ohm test question and it is a valid point.

This is a great video, but you said never short the 5v reference to ground or computer damage can happen. but if the you are jumping the 5v to signal to see cicuit integrity of signal wire, and lets say the signal wire was shorted to ground seems like that can cause internal damage to computer. The reason I asked because 0v in the scan tool can be caused by a short or open in signall wire. not trying to judge the video maybe something I am missing. I have your E-Book and its great.

Thank you.!!

good job teacher ScannerDanner :D

There will be current flow but it is even lower than you stated as it is a 5v source not 12. In fact the sensor itself pulls this "bias" voltage to almost ground at times. So there is absolutely no danger in doing this test. Also the internal resistor may be even higher ohms than I stated.

I done this same test on a car at work the other day, but it had a FTP sensor performance code. If you touched the top of the sensor the voltage pid on the tech 2 would go nuts.

thanks

Great explaination and easy to understand 👍❤ , btw i think someone was sleeping during that class ! I hear a weird sound in a background lol 🤣

@EVERXXXX You could certainly do that, however in my experience a shorted reference circuit almost always comes back to life after fixing the short so I'm not to concerned about it.

The kid snoring in class will be the tech at the Chrysler stealership who replaces a gas cap 3 times for an evap leak, when it really there was a cigarette-sized hole in the purge line caused by rubbing against the ECU harness (COUGH THIS HAPPENED TO MY CUSTOMER). The passionate tech's will prevail.

@ScannerDanner If you check the signal wire for a short to ground you would have to unplug the PCM for a proper test and we want to avoid that step if possible. I suppose you could.....

@Username64870 Nice! I agree completely of course :)

@ScannerDanner leave the PCM plugged in, make sure your ohmmeter is reading in the kilo ohms or that it's just not reading zero. And no the ohmmeter will not hurt the PCM on this test.

I have watched this three times and I got it the first time. Great information but most techs can't do that. I have one question though: Why not just replace the sensor? I do have a scan tool but I guess the stealership does not. They replaced the fuel pump under warranty and a couple of days later the car will not start. I have an Innova 3040c and P0452 is what it told. The stealership told me that I needed new spark plugs that cost $505. I went down to the stealership and observed the plugs.(not an old car). The plugs were fine. Not my first car. I priced out the part and it is $33 plus tax. Look where it is located though. I appreciate what you are putting out there for facts. There can be so many other things wrong with an EVAP low fail. I have 0 degrees F here with a twenty mile an hour west wind. I know what I can do but that is why I have four vehicles. You would think that the stealership would take some ownership on their warranties. I hate to be at 75% operational. It is Minnesota though and I only have one non-heated garage for cars/trucks. You have to get the vehicle in the garage first though.

you mention here dont jum 5v ref to ground,that means with jumper wire or testlight,but if i want to check 5v ref voltage with multimeter,i can do that? one lead to 5v ref ,other to ground,scale on 20v DC. its dwont hurt that regulator?

No! You wouldn't want to put direct 12v into the O2 signal wire. There is some protection inside the PCM for the O2 signal circuit. I just wouldn't jump direct 12v to it. Use your body as the resistor and do it that way.

scannerdanner rocks,cool

thank you for the tip. oh and what previous comment?

@natesmoggdogg Yes it is

Hey Paul, happy new year. Ive got a question on the design with the resistor being connected internally on the signal line. You say unplug the connector and you should see 5 5 and 0, and that if you see that, then you can replace the sensor as the signal cant have an open or short. What if however the signal wire was corroded and you unplugged the connector? Would you still not be reading 5 5 and 0 due to there being no current flow on the signal? I would assume this is where jumping the ref to the signal would come in to play as if there were green cruddies on that signal wire then we would have a voltage drop at the computer? Thanks alot

I’ve tested my FTPS using a vacuum pump and back probing the sensor connector with no vacuum on the sensor I was reading around 1V but once I applied say 10”hg I then was reading around 4.5V. So my question is what should voltages be for any given amount of vacuum?

Hi ! a question : I have an Opel (group gm) i suspect an evap solenoid valve fault, only i do not have a fault code displayed on the dashboard. Is it possible to find faults with a pro diagnostic device, which would not be indicated on the dashboard of the car? thank you ! ( Thomas, from France )

Paul, I love your videos. I also follow Daniel Sullivan's videos and he is a big fan of "ghost" voltage and specifically how it tells you something important - namely that a circuit is open. Short to ground would be 0V, ghost voltage is open. Do your meters not show ghost voltage or is there another reason you don't mention it?

Hello Mr Danner Thanks for this information My question is about jumping 5 v reference to signal wire. What if the signal wire was shorted to ground but you jumped 5 v reference to signal wire. Is that same as jumping 5 volt reference wire to signal wire to ground wire in the bottom

@jtech23 LOL you caught that! This poor kid has sleep apnea and he was sitting right next to the camera. Did you see my face when that happened. It was kind of funny. He is really trying, I don't fault him.

Should the resistance values for the FTPS be the same as the MAP sensor? While testing the MAP sensor with vacuum pump and multimeter, the more vacuum I put on the sensor the more voltage I would read, but on the FTPS tested the same way, as soon as I’d get virtually any vacuum on it it would go straight to full voltage.....is this normal?

Is it common for cars such as a ford f150 and ford SUV to use the same voltages to set up a fault or typical run conditions such that you could take one from one of these cars and adapt it with fittings to the other and have the system work? :-) My 04 F150 has a inline sensor and is difficult to find( and is expensive as they want to sell you all the fuel lines with it), and the other Fords have a in tank plug in unit that you can find anywhere for cheap! Thanks for your time and expert information.

ON THAT TRUCK DID YOU REPLACED THE FUEL PUMP? OR JUST THE FUEL PRESSURE SENSOR. I AM WORKING ON A 2000 S10 2.2L AND I DID REPLACED JUST THE SENSOR BUT I STILL HAVE THE CODE.THE SIGNAL ,GROUND,AND 5V REF ARE OK.I HAVE P 0452 AND P0462 WICH IS FUEL LEVEL SENSOR LOW..THANKS

@paulsjunkcars LOL Thanks

I have your Ebook but, I was wondering if you sell them in a regular book? Thanks again for the great video.

Would a Fuel tank pressure reading of -33 mmHg with the fuel tank lid off indicate something is plugged and pulled vacuum, if the sensor tests well? Threw a code for evap vent, tried to actuate it manually with scan tool and a message popped up on my tool that the vacuum is too high and stopped it from opening. Haven't really looked at much yet I suspect something is plugged or stuck. Buddy's truck, just doing preliminary research.

If the open circuit on the signal/ground wire was after the voltage sensing circuit wouldn't the voltage SC read 0 volts? As it would no longer have a ground connection to read the 5 volts comming from the signal wire or "resister" or whatever thats called. So a short after the sensing unit would cause a zero volt reading, is that correct?

i can test someway oil pressure sensor to? shorting out refrains to signal and looking at instrument panel cluster so see going to high pressure?

2006 Chevy Optra (p0454, then p0452) - this is the same car as Suzuki Forenza/Reno(USA) Hello Paul, I have followed your Video instructions and below are the tests i have performed on the FTPS problem so far. I am a DIY'er and seem to have hit a block in the road. I have no wiring diagram for this cars FTPS circuit as i cannot find one. I have a service manual for a 2004 Optra and it doesn't list anything for the FTPS circuit or ECM pin layouts NOTE: I do not have a Fancy dancy scanner with square waves etc. I only have a simple Actron scanner CP9580a and a DMM and test light. Here is what i have diagnosed so far: (( CONNECTOR UNPLUGGED )) With Key off ------------------- 1.) I have continutity on the ground wire(black) With Key on Engine off ---------------------------------- 2.) 5Volt Reference - tested 4.99V on the reference wire (gray) 3.) Signal Wire - jumped 5Vref to signal and backprobed the signal wire (ecm side of connector). Test showed 4.99v proving no connector fault. (( CONNECTOR PLUGGED BACK IN )) 4.) FTPS test - removed FTPS from Fuel Tank Pump assembly and applied -10kpa vacuum on the sensor and it ranged from 1.3v - 4.74v After releasing the vacuum pressure voltage returns to 1.3v ,,,,Did test 2 or 3 times to verify. 5.) Purge Valve - removed from car and applied voltage to test valve open close operation while applying vacuum - Valve opens. Also listened to the purge duty cycle with stethascope and valve was rattling away. 6.) Vent valve - removed from car and applied voltage to test valve open close operation while blowing thru it - Valve closes. 7.) Gas cap is brand new. 8.) The Drive Test Diagnosis - The MIL IS ON !!!...... After resetting MIL and now 93km later the "Evap Drive Cycle Monitor" is complete and "DTC P0454 is confirmed". P0452 hasn't reappeared as yet, but rest assured it will as i have done this a few times already over past year. With the DMM connected to ground and backprobed to the signal wire on connector (ecm side) i observed the Voltage reading while driving for 15 minutes. At very low load The signal was perfect (1.4V-3.1V). Went home let car cool and retested. Drove same distance never tromping on throttle. Stopped, waited a few minutes and restarted car and the MIL went off (expected). All the drive time the FTPS signal Voltage was perfect and MIL went off. SO I APPLIED SOME FORCE TO HER ON THE NEXT TRIP FLOORING THE GAS PEDAL WHILE OBSERVING THE DMM VOLTAGE and sure enough the voltage dropped below threshhold and went haywire at times. This resulted in the MIL coming back on IMMEDIATELY after the second attempt. I am almost sure that the code is being set when there is positive pressure in tank, because freeze frame data indicates PURGE % = 0. Below .1 Volts i think is the threshhold which has to happen on 2 consecutive trips for the MIL to come back on and my testing confirmed that. But i have reservations about going out and replacing the sensor (throwing money at parts) until am absolutely sure about the fix. 9.) Commanded the Vent valve closed with my scanner and applied .5 psi shop air from the evap hose before the purge valve. Everthing seemed to hold pressure but i have no way of determining this as I dont have a fancy smoke machine with pressure gage). So i attached a balloon to the Vent Solenoid end of EVAP system and waited 10 minutes. Came back and the balloon was still holding all pressure, so it seems that i have no leaks, thus no leak codes....dah!! PAUL PLEASE ADVISE, AS I AM NOT SURE WHICH FORK IN THE ROAD TO TAKE FOR THE NEXT STEP. I dont have a wiring diagram showing the FTPS circuit nor do i have a pin layout of the ECM to do a short / open testing on the REF & signal wires. You mentioned in your video not to worry about ground wire in this case and it makes sense. If anyone has the FTPS wiring diagram and ECM pin layout i would be forever grateful as i cannot find them anywhere on the WWW. Whats really puzzling is that I have a 2004 Optra Service Manual but it doesn't show any information regarding the FTPS. PS> I LOVE YOUR VIDEOS - YOU ARE THE BEST TEACHER OUT THERE BAR NONE !!! .....well maybe the legend scotty K.

Never mind... just read your post below!

Thank you this was very help full but is it possible to check this by check resistance between the 5v wire and the signal wire?

Hi can a bad tank pressure sensor cause for the p0449 code? thanks

Sorry for the previous post. What I was going to mentioned just for reference is that most GM vehicles have a 1.47-1.50v reading on the tank pressure sensor with no vacumm or pressure in system. Thanks

why is someone snoring through the whole video

I am trying to learn about vehicles and your instructions are very easy to understand. As someone that is now beginning where should I start. How do I get a hold of the circuit

Great video, Paul . Is this test done with the sensor plugged or unplugged?

I know this is an old video, but have you ever seen a P0451 on a Ford Pickup? mine is a 04 5.4l F150 Lariat. I have looked at the sensor and grounded the signal and the voltage went to 0 and took the 5v to signal and got 5v. The voltage changes but I guess not enough. Suggestions on how to proceed?

Good video i have same troble code but only happen when summer is here, i check wires remplace connector, ecm and the sensor still having the low signal from fuel thank pressure sensor, i saw on google the a/c pressure switch it may be affecting. What other possibility can be it??

Paul. If we had the second design (one with internal resistor) as stated at 15:00 to 15:30, and there was a short to ground in the signal wire between the connector & pcm. Then we unplugged the connector, then the scan tool would read 0 volts as in the top design and not 5 as you stated. Would that be correct?

I'd just call them variable resistors and get away from people getting caught up on the potentiometer confusion. The potentiometer is a variable resistor as well..

nice tutorial but I had one question, what if the signal line and ground are reading at 4.96v like the 5v and signal line? bad grounding?

if we didn't have a wiring diagram we could use the test light connected to the battery positive to find the ground? in the ground it would light up while in the signal it wouldn't light up?

For an average home owner that does not own an advance scan tool, can I use a volt meter link in series with a test light and use the reference 5v to test the ground and signal wire. I know that I can do a continuity test to verify ground also but what about the signal wire? Will that damage the computer module?

Great video! I had the same concerns as others about jumping VREF to signal, just in case the signal wire has a short to ground. Would testing continuity from signal wire to ground be a good enough pre-check? Also would it not be safer to suggest building a 5v power supply tool to keep in your box instead of ever jumping a VREF? Or why not just use a 12v power probe?

excelente

AT 16.47 in your video, you are jumping Signal to Ground. When you jump Signal to Ground, it is like kind of short(basically connecting + and -) there will be a current flow. If you look at 16.47, Singal REF wire have >>>> 100 kilo ohm resistor connected in series with Signal wire and you are jumpting that signal wire to ground. In a series circuit current is same across every point. I assume 12V/100000 gives .00012 amp(ohms law), very very less, so that is why it is ok to jump Signal to Grd ?

might be a dum question , when you have a 5-0-0 sensor disconected and "no wiring diagram" how do recognize wich of the to 0volt wires is what . (one of the two will have continuity to ground?)

I did the same test on a oil pressure switch while looking at data jump the wires I got my 5 volt but my pressure reading stay the same any advice will be helpful

So, in the top example at frame 16:46, you say that jumping the 5v reference to ground will fry the pcm regulator. If i'm following what you are saying, why would they make an expensive pcm so vulnerable to a short to ground?

The guy who ran the code reader test , also put my new fuel-pump in , He said the Evap was good , but the code still said PO446 on my 2000 chevy Blazer.. Was he B.S. me.. Is the canister purge valve & vent valve solenoid the same part ?

Quick question: So I don't have to check for pressure in the system? My car car 2011 Nissan altima s 2.5. And I was planning on doing a pressure test first. I think I'm missing some information. Or I'm not understanding the code. You didn't suggest it, so now don't know if it's necessary. Code: p0452 sensor/switch low. Thank you very much for your videos.

Sorry, I forget this point, Let say we have A B and C as three points. A is Signal Reference connected to B via a resistor of 100 Kohms in series then you are jumping B in series with C (ground). As I explained between A and B current is .00012 amp(12v/100kohms), then current between B and C will be huge(right, bcz u have sorted). So the current at point A is equal to .00012+ current (between B and c). Since current is same at all point A, B and C, will not we fry PCM?. Again I may be stupid ?.

Hoping you'll see this ScannerDanner. I been fighting an P0455 code on my 06 Silverado now for quit some time. I have 'verified' no leaks in the system. Using an SnapOn scan tool the (new) tank vent valve NEVER closes, but, can be closed manually with the scan tool, and I've verified i does seal off. Also the purge valve continually stays open and never closes. It's like the tank sensor is giving the PCM false readings, or there is something wrong with the PCM. The PCM had been changed after my local dealership said it was giving some strange readings. It was replaced with a used (reflashed for my vehicle) PCM. I've tested the tank sensor wiring like you showed here and I get the 5v reading on the scan tool, so I know at least those two wires are good, but, could a bad ground from the PCM be causing my problem. The sensor voltage NEVER changes from a constant steady reading sitting at an idle, or driving on the highway even after trying 2 different tank sensors. one sensor stayed at 1.2 volts, and the other stays at 1.5 volts on the scan tool. 'COULD' it be the blk ground wire back to the computer causing this, or something else? This thing is about to drive me NUTS!!!!! LOL! WHAT could be causing both valves to stay open ALL the time?

If you are truly interested I can get you in touch with our admissions staff and they can answer that. We have a lot of financial aid available so cost is greatly affected by what you qualify for. Send me a PM with your contact info. and I will have someone contact you if you like.

I think you have to use a 5000 resistor instead wire in case you have short to ground in signal wire just for safety for the 5 reference circuit

AN IN THE 5-0-0 SYSTEM INSTEAD OF A JUMB WIRE WE PUT THE TEST LIGHT TO BATTERY POSITIVE AND LOOKED AT THE DATA WE WOULD NOT SEE THE INTEGRITY OF THE WIRE? THE SIGNAL WOULD NOT GO UP? WE DON'T HAVE A PULL UP SYSTEM?

No you cannot. If the sensor is unplugged and you read 0 volts on the signal wire, it is NOT a ground, it is still the signal wire, there just isn't any voltage on it with the sensor unplugged.

I have a 2008 f150 4.2 L and I'm getting a code of P0453. I did some checks and saw my pressure sensor value was NOT moving, so I decided to change it out. After changing it out, I'm getting a stuck negative pressure. After looking at this video, I attempted to test the sensor, but I'm stuck at determining which are the two wires to jump. I don't know which one is the return signal wire in order to jump it with the 5 volts reference because I'm getting low voltage (millivolts) in the remaining both wires. When I unplug the sensor, I'm getting ~6000 pa. And, when i plug it back in, I'm getting -1760 pa. Could you help me to identify which of the other two wires have to be jumped and to check the integrity of the wiring circuit? Thank you very much.

I can hear someone snoring. Was that Kenny? j/k

Hi there sir I've got a 2011 silverado it's throwing a p0449 code I changed the evap vent solenoid and it still comes back on the vent solenoid is clicking when the vent solenoid is hook to the charcoal canister I can't put fuel in it but I can when I disconnect the line from the canister will a bad tank pressure sensor cause that

how do I test a pressure sensor, 04 ford escape it has 2 hoses side to side the signal wire

What's missing which is very important is where the scanner is plugged in when ref is jumped to signal.....it has to be connected to the PCM?? But where and how?

Can bad FTP sensor cause poor acceleration?