Chevy Colorado - EVAP Trouble P0449 & P0017
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Date: 2020-08-05
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Comments and reviews: 10
busjockey1
Good job explaining how the computer checks for opens and shorts. For those vent solenoids Eric how much current do they usually pull? Your spot on about meter usage, have to understand what the meter is telling you and be aware of circuit operation. Thermo King Computers put out a bias voltage on the ac clutch circuit, not battery voltage but it is around 4. 2, 4. 3 Volts, you will see this value with your voltmeter in the power and ground of the connector unplugged. So to test dynamically either plug the circuit back in to check or how I like to do I use the Loadpro to fool the computer that the load is plugged in. Takes a minute for the computer to recognize a complete path but when it does if I have a good circuit path it will give me full system voltage on my meter which is the volt drop across the Loadpro resistor.
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Good job explaining how the computer checks for opens and shorts. For those vent solenoids Eric how much current do they usually pull? Your spot on about meter usage, have to understand what the meter is telling you and be aware of circuit operation. Thermo King Computers put out a bias voltage on the ac clutch circuit, not battery voltage but it is around 4. 2, 4. 3 Volts, you will see this value with your voltmeter in the power and ground of the connector unplugged. So to test dynamically either plug the circuit back in to check or how I like to do I use the Loadpro to fool the computer that the load is plugged in. Takes a minute for the computer to recognize a complete path but when it does if I have a good circuit path it will give me full system voltage on my meter which is the volt drop across the Loadpro resistor.
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newjerseybt
Almost the exact situation occurred when a electrician's helper I hired was helping me rewire a rat's nest created by a previous homeowner. The helper was in a trance for 15 minutes staring at his DVM which was indicating about 70 volts AC on a wire that shouldn't have been connected to power. I ran and got my old fashioned Simpson 260 which has a much lower impedance than his DVM and got a 0 volt reading instead. He acted amazed that I found this and I was amazed that he was not aware of phantom voltage from capacitive coupling since he was an electrician. Maybe he was milking the job. who knows.
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Almost the exact situation occurred when a electrician's helper I hired was helping me rewire a rat's nest created by a previous homeowner. The helper was in a trance for 15 minutes staring at his DVM which was indicating about 70 volts AC on a wire that shouldn't have been connected to power. I ran and got my old fashioned Simpson 260 which has a much lower impedance than his DVM and got a 0 volt reading instead. He acted amazed that I found this and I was amazed that he was not aware of phantom voltage from capacitive coupling since he was an electrician. Maybe he was milking the job. who knows.
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AVM
Great video Eric! Don't worry you explained it just right.
when I was in training many years ago I was taught how to use a meter and how to diagnose with it and you hit all my fundamental rules right on. back probe only, circuit intact and loaded, negative lead to good known ground at all times, and use voltage drop to check for resistance only use ohm meter to check component resistance.
I've tried different gadgets and doodads but always went back to my meter. i do really want a scope but not the price tag. lol.
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Great video Eric! Don't worry you explained it just right.
when I was in training many years ago I was taught how to use a meter and how to diagnose with it and you hit all my fundamental rules right on. back probe only, circuit intact and loaded, negative lead to good known ground at all times, and use voltage drop to check for resistance only use ohm meter to check component resistance.
I've tried different gadgets and doodads but always went back to my meter. i do really want a scope but not the price tag. lol.
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Intrade
Do you not own the LOAD-PRO test leads? from Dan sullivan? Because you can test the whole wiring harness for voltage drop with the push of the button with the patented load pro lead. Even the shroedinger box now owns the leads i think i might have managed to convince him to buy them ohms law matters dan sullivan is 100% correct. Your methode also works but Dan sullivans tool is like the ultimate time saver.
i know one can have to much tools but that accessory is a must have if time is money.
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Do you not own the LOAD-PRO test leads? from Dan sullivan? Because you can test the whole wiring harness for voltage drop with the push of the button with the patented load pro lead. Even the shroedinger box now owns the leads i think i might have managed to convince him to buy them ohms law matters dan sullivan is 100% correct. Your methode also works but Dan sullivans tool is like the ultimate time saver.
i know one can have to much tools but that accessory is a must have if time is money.
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Randy
Cool video Eric O, I had an 04 Colorado ( bought brand new in 04) with the inline 5 / 3. 5 liter I believe it was, and I never cared for that vehicle, It started running like crap at around 75 to 80, 000 miles using in my opinion more gas than it should have, and would occasionally stall but start right back up and run OK for a bit and then do it again in a month or 2 very annoying!
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Cool video Eric O, I had an 04 Colorado ( bought brand new in 04) with the inline 5 / 3. 5 liter I believe it was, and I never cared for that vehicle, It started running like crap at around 75 to 80, 000 miles using in my opinion more gas than it should have, and would occasionally stall but start right back up and run OK for a bit and then do it again in a month or 2 very annoying!
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Jan
Excellent stuff showing the need to load circuits like solenoid valve control circuits when checking for command signals. When doing this with a multimeter, it should be equipped with a LoZ setting, but, typically those only come on specialized or high end multimeters. It's a lot cheaper to carry around a 100 Ohm/3W resistor (which doubles as a pair of backprobes.
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Excellent stuff showing the need to load circuits like solenoid valve control circuits when checking for command signals. When doing this with a multimeter, it should be equipped with a LoZ setting, but, typically those only come on specialized or high end multimeters. It's a lot cheaper to carry around a 100 Ohm/3W resistor (which doubles as a pair of backprobes.
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Pet
I'd love to see a full nerd explanation of what was going on. I would think the impedance of your test light also has an effect on the meter reading. I'm a big fan of voltage (drop) testing of loaded circuits. I was worried that you may have 'fixed' the problem by disturbing the wires when you unplugged the connector.
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I'd love to see a full nerd explanation of what was going on. I would think the impedance of your test light also has an effect on the meter reading. I'm a big fan of voltage (drop) testing of loaded circuits. I was worried that you may have 'fixed' the problem by disturbing the wires when you unplugged the connector.
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Pete
I wonder if that is why I was getting battery voltage on my cheap voltmeter at the O2 Sensor wire. I keep getting a periodic P0161 code. I will need to get a test light because it was even showing continuity between the two heater wires.
Thats for that lesson there Eric. It does make sense.
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I wonder if that is why I was getting battery voltage on my cheap voltmeter at the O2 Sensor wire. I keep getting a periodic P0161 code. I will need to get a test light because it was even showing continuity between the two heater wires.
Thats for that lesson there Eric. It does make sense.
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watajob
So, let me see if I have this straight: The PCM signals the solenoid to open by yanking it's ground forcing the voltage to use the solenoid's ground, thereby seeing 0V, signifying that it's working not just passing current? Sheesh. What a lovely idea. :(
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So, let me see if I have this straight: The PCM signals the solenoid to open by yanking it's ground forcing the voltage to use the solenoid's ground, thereby seeing 0V, signifying that it's working not just passing current? Sheesh. What a lovely idea. :(
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splash
Lol
After watching the series on the Colorado, that lasted more than some tv shows, it seems like you didnt take the easy ones.
That probably already knew that they werent gonna get to the bottom of it, and thats why it got shipped off!
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Lol
After watching the series on the Colorado, that lasted more than some tv shows, it seems like you didnt take the easy ones.
That probably already knew that they werent gonna get to the bottom of it, and thats why it got shipped off!
reply
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