GM EVAP Vent Solenoid Testing




What do you think about this video?

James Ruggero: No matter how you cut it, someone sells a lot of parts! and that's the idea I guess. Call it a forced economy. I think I remember the older gm cars by jumping the underdash connector a certain way ,the pcm would cycle all the system components. Now why don't they incorporate that anymore? Oh I forgot, it sells more scan tools! All this for clean air on such minute magnitude is a joke .Before long they'll be outlawing beans in your diet. Excellent explanation , but look at the what it took to get that far. I'm sure you didn't just decide today this is how it works, They have no standard to abide to, Over engineered troublesome designed systems .Gotta be a better way. 

Thee3rdprophet: Monkey Chart

Ken nomura: Great video Danner! i got a question, if the solenoid shorts, that could possibly fry the driver on the pcm right? so in that case we would have to replace the solenoid and the pcm? thanks a lot!

albdesi: SAVE YOUR SELF PAIN AND AGONY AND BUY A POWER PROBE!!

Garick Newtzie: awesome video. I feel smarter and I think you just helped me fix the problem

Dave Gibson: Excellent video - great teaching style. Thank you for posting. 

yoyomin: you sure know what you are talking about!!! very helpful.

Ras Bongo Natty Tafari: Great Lesson......where do u get ur wiring diagrams?

abochavez: What if there is voltage on both sides of the connector unplugged key on. I have had several of these evap codes on different vehicles and I frequently see 3.5 volts on the ground wire unplugged not just the vent solenoid but purge solenoids too. No shorts or opens. Computer disconnected. When computer is connected the voltage shows 3.5 volts. The 12 volts supply wire is always good. Bad computer right? I've also had 12 volts coming from both wires of the connector unplugged on a fuel heater. Followed it to the computer again. Am I missing something before calling this a computer?

Gabriel Velazquez: Excellent diagnosis. Love how you confirmed the integrity of the driver at the end by commanding it on and off. I always like to manually control drivers whenever the option is available. I wonder if maybe you could view the voltage on the control wire through the scan tool, while also commanding it on/off. Of course, it is always important to understand what is going on in a circuit. This vid did that

foxholewilly: Paul, one thing I'm wondering: Why was there NO ghost voltage on the voltmeter when the lead was connected to the control-side terminal of the vent solenoid? With the solenoid open, and the control driver off, wouldn't that single piece of wiring harness just be an extension of the voltmeter test lead going nowhere, and we would still see ghost voltage? What was different at that point? Is the base of that driver transistor a current path here? What am I missing?

ScannerDanner: no problem at all, glad you fixed it!

ScannerDanner: the test light is the load. most test lights will draw less current than the solenoid itself would draw. you should always measure the current draw of your test light before doing this kind of testing. most of the incandescent bulb test lights draw about 200ma.

ScannerDanner: If you energize the solenoid with a test light, that just checks the solenoid and the feed circuit. To test the control wire and the PCM driver you must use a scan tool to turn the driver on or you have to meet the conditions where the PCM will normally turn the driver on. That is the only way. Of course you can use the test light in place of the solenoid for the test, but the driver must be turned on and you cannot do that part with the test light.

ScannerDanner: @foxholewilly When I say "doesn't support current flow" I mean no measurable amount with our conventional meters and scopes. There is some and it is in the micro amp range. I don't have anything that reads micro amps, nor do I have the need to.

ScannerDanner: @ScannerDanner It is too easy using a power probe to apply the wrong polarity to a circuit. I personal don't use one, nor do I feel the need to. Just a regular old incandescent style test light is just fine for 99.9% of driver testing that I showed in this video.

martin mejorada: In addition of after checking the control side and power side of the circuit, you can energize the solenoid with the scanner and apply vacuum with a hand vacuum pump. If the the vacuum doesn't hold then surely the solenoid is bad. Btw, I purchased your book very awesome.

foxholewilly: @ScannerDanner Ok, I see it now. It must be the "voltage sensing circuit" before the transistor in the pcm giving a path to ground (even though that "sensing circuit" dosen't support "current flow"). Following the path here, I guess it resembles having just two voltmeters connected to each other. I think I'll try putting two meters in series and see what voltage they read - will it be a negative .03v? This is fun. Thanks for your time, Paul.

ScannerDanner: i have a video on this.

contagiousFX: Using a test light to test computer circuit is not ideal correct?

ScannerDanner: Anytime my friend!

104snake: i have a p0446 code.can you help?

ScannerDanner: I'm sorry man, I don't think I can help any further over the internet. Too bad you were not closer to Pittsburgh PA, I would be more than happy to take care of you for free at the school.

Tim R: Thanks again for the great video.

ROWDY8780: Thank you for taking the time to try to help. It is greatly appreciated. :) The car runs great but it has been a nightmare of electronic issues the last few years; Worst of which, was trying to figure out what why the wipers and radio quit (Solder joint cracked in BCM). It could just be time to look at retiring it for something newer. lol I'll update you on what the problem was; if I figure this mess out.

StealthShadow5: In the second test if the test light doesn't comes on its mean you have a shorted to ground control wire. And is will be easy find the short because that cable will have steady 12v from the jumper cable of the battery positive. then it is a matter of search the voltage drop in the cable to find the short. Well that what I think and again sorry for my English

ScannerDanner: use a t pin for the pcm connector the make yourself a long jumper wire with alligator clips. be sure to insulate the end under the hood just in case. also use a jumper wire for you voltmeter neg lead too. this way you don't have to hold anything and you can focus on driving

Prabath Weera: Are there any insulateted t-pins where crocodile clips can be hooked up safely and what are the best wire tapping tools.Thanks in advance.

felplay vina: Thank you Paul for the time to replay and thank for the update of your book.

ScannerDanner: you heard a click, that's good but you must also check the function of the solenoid. you should be able to blow through it not energized and not be able to blow through it energized. This is a normally open valve so by your description of having trouble filling your tank, either the valve is stuck closed or there is a blockage in the vent line

Robert Wood: Thanks brother

stingray300m: pedel really fast the rpms pulsate instead of rev up p1406 is the only code and there is no carbon deposits on the valve and the pantal goes in and out like it should no sticking and the omes reading is ok i have a good 5 volt refrance over all the only thing i see wrong is the feed back voltage is too high its supposed to be in the millavolts range like 12 millavolts idk please check back with me

Dan Laabs: All I can say is Amazing!! This answered all my questions of why there was constant 12 volts at the Solenoid,and it would not operate off the bench and on the truck at idle!! Thanks ScannerDanner..

StealthShadow5: and the other option is instead of using the feed of the solenoid wire using a cable that go from battery positive to the placed t-pin in the control wire and check if the light bulb lights up. These 2 tests it can perform and verify that there is a failure in the control wire right? Sorry for my english :)

r8er4everd: Yes, BATT voltage and ground can be applied with the switch. And without pushing the switch if the probe tip touches a grounded source, the light will go green. But if it touches a voltage source it has a red LED that lights. So in a sense PPIII and DMM sorta same. So any suggestions to a good scan system that a work-from-home mechanic should look into? Local part store has a OBD1/OBD2/ABS scantool,but it does no live data or sel/relay acctivation only FF all for $500.Only 1 can find under 1K.

ROWDY8780: Sorry for delay. Been a long week. There are 2 harness connections at PCM (Upper connection nearest windshield & lower nearest wheel arch). I didn't find any solid white wires in the upper connection. The lower connection has 2 solid white wires coming in and 1 off-white (No other markings, stripes, etc...on any of them). Both of the solid white wires have 12V and the off-white has 9.5+ (KOEO for all three wires tested). My scan tool (AutoXray 6000) does not have bidirectional capability.

ScannerDanner: not sure off hand. I have at least two or three GMs with the linear EGR valve with issues. maybe search EGR valve?

ScannerDanner: @fivefortyeye540i Thanks for the comment and the compliment!

Joe Hernandez: If you do more than three shakes on your lead you are just on vacation 17:25

ScannerDanner: what is the voltage with just the key on engine off

StealthShadow5: I mean continuity test*.two other options which come to mind are (can you hear crazy but when you dont have the right tools you have to improvise) put a t-pin in the ecm plug and disconnect the plug and place the test light to ground battery and place it in the t-pin of the plug of the ecm and then jump the 12 volt feed of the solenoid to the control wire and check if the test light comes on. The only danger that I find this test is if the control wire is shorted to ground will blow the fuse

Robert Wood: Like Paul said you can aggressively twist it with pliers, channel locks or lightly adjusted vice grips. I replaced my 1993 3.1 recently and when you get it out take a knife tip and snap out the o ring. There should be a shaft from the oil pump that may or may not come out with the cap. Mine did. Good luck.

ScannerDanner: It is what we call a dummy shaft distributor. It is still there to drive the oil pump as the distributor used to do. It will come out. There is a rubber o-ring type seal that is most likely hard as a rock. It is ok to get aggressive with it.

Joe Riley: THE POWER PROBE 3 IS BASICALLY A VOLTMETER WITH A SET OF LEADS THAT YOU CAN APPLY POWER OR GROUND TO ANY CIRCUIT AT THE TOUCH OF A BUTTON.ITS VERY HANDY BUT YOU CAN DO THE SAME WITH A SET OF JUMPER WIRES IF WANTED. YOU WILL GET IN BIG TROUBLE IF YOU DONT KNOW WHERE TO APPLY THE POWER OR GROUND,THIS TOOL APPLIES FULL BATTERY VOLTAGE AND FULL GROUND.IF YOU DONT KNOW HOW TO READ A WIRING DIAGRAM AND KNOW CIRCUIT DESIGN I WOULDNT MESS WITH IT. I OWN ONE AND RARELY USE IT MAINLY I USE IT TOFINDSHORTS

ScannerDanner: @foxholewilly Oh ok that was very observant of you! In my experience with both ends of a circuit open yes you will see this "ghost voltage" as you call it. (From what I found if you zoom in on it and measure its frequency it is 60hz which no coincidence is the same frequency our residential lighting systems run.) So I would call it "noise". Anyway to answer why it was not there. First I do not know the PCM board as well as I would like to but I would say there are some......

ScannerDanner: your welcome and thanks for the comment

felplay vina: Hi Paul, I'll have to work on my neighbor's car with po110 po159 po443 po157 po160 the history of this car somebody change sensors but the codes are back again, and I think start with po443 fix it first, what do you think about it? any help to start I will appreciate.

ScannerDanner: Can you apply a power or a ground to a circuit with just the touch of a button with this tool? I know the older power probes do this. Also what is the voltage threshold that will light the green LED indicating a power source? There are other concerns I have with this tool too. Take a ground side switched solenoid that is not being grounded yet and check the control wire. This tool will ID the circuit as a power feed, but what it really is, is a switched ground. I suppose a DMM does the same.

ScannerDanner: @contagiousFX It is a ground side switched circuit, so with the solenoid open there will be 0 volts all the time on the control wire regardless of circuit activity (driver on or off)

Robert Wood: Thanks brother for another great video. I have a 1997 LeSabre with a p1655 EVAP Purge Solenoid Control Circuit code. My scan tool is not bi directional and I wanted to know the best way to test this circuit. Can I use the test light to activate it ? Thanks brother

Cert: Building stuff is always in my family gene. My dad is a new york auto technician and taught me everything I need to know about cars. Now I sell car parts online to suppliment my income. So it does help when there's good guidance.
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GM EVAP Vent Solenoid Testing 4.9 out of 5

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GM EVAP Vent Solenoid Testing