Jeep Patriot: P0339 Bucks, Tach Quits Then Dies?
video description
My diagnosis on mechanical things is to sell it while it's running.
I learned the hard way about aftermarket electronic stuff with GM ignition modules and Toyota reverse lockout transmission modules. Once we went back to OEM, problems went away.
Date: 2022-04-15
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Comments and reviews: 9
Matty
I may have the answer to this one. A hall effect sensor is fundamentally two components. Without going into crazy detail the first component is the 'sensing element' which is what effectively detects the tooth moving over the sensor. The output of the sensing element is a very very low voltage (called the hall voltage) which is created by the metal trigger wheel passing in proximity to the magnet in the sensor. This voltage is far too small to run to the ECU directly as it will be lost in the noise. Hence the second element is an amplifier, or more accurately a comparator. It looks at the output of the sensing element, and when it reaches a threshold voltage it 'switches' the output to the supply voltage (in this case +5V.
The likely problem with the aftermarket sensor is the skew (or time taken) between the trigger wheel passing over the sensor, and the comparator switching to +5v. This could be because the transistors used in the comparator are substandard and slow, or the actual hall effect sensing element is a bad design. By bad design I mean it doesn't have a constant voltage/position relationship with the toothed wheel on the crank, and likely triggers at different times based on things like RPM and temperature. I'm not talking a big difference here either, I would estimate a fraction of a tooth.
Eric has tested the waveforms in the past, however to do a real test you would need to compare the OEM sensor to the aftermarket on the same trigger wheel, at the same exact RPM and same exact time. I expect there will be a small phase difference in the waveform, probably in the order of < 5 degrees.
The reason the car quits working is the ECU is constantly looking at the cam/crank phasing. It notices these discrepancies and then enters limp mode.
(Electrical engineer of 14 years and I've run into this before)
reply
I may have the answer to this one. A hall effect sensor is fundamentally two components. Without going into crazy detail the first component is the 'sensing element' which is what effectively detects the tooth moving over the sensor. The output of the sensing element is a very very low voltage (called the hall voltage) which is created by the metal trigger wheel passing in proximity to the magnet in the sensor. This voltage is far too small to run to the ECU directly as it will be lost in the noise. Hence the second element is an amplifier, or more accurately a comparator. It looks at the output of the sensing element, and when it reaches a threshold voltage it 'switches' the output to the supply voltage (in this case +5V.
The likely problem with the aftermarket sensor is the skew (or time taken) between the trigger wheel passing over the sensor, and the comparator switching to +5v. This could be because the transistors used in the comparator are substandard and slow, or the actual hall effect sensing element is a bad design. By bad design I mean it doesn't have a constant voltage/position relationship with the toothed wheel on the crank, and likely triggers at different times based on things like RPM and temperature. I'm not talking a big difference here either, I would estimate a fraction of a tooth.
Eric has tested the waveforms in the past, however to do a real test you would need to compare the OEM sensor to the aftermarket on the same trigger wheel, at the same exact RPM and same exact time. I expect there will be a small phase difference in the waveform, probably in the order of < 5 degrees.
The reason the car quits working is the ECU is constantly looking at the cam/crank phasing. It notices these discrepancies and then enters limp mode.
(Electrical engineer of 14 years and I've run into this before)
reply
Lammergeier350
22: 10 Nice.
I remember doing the counter monkey ASE test, back when I thought that actually meant I knew what I was talking about. Tach drop and a crank no start was always touted as 'replace the crank sensor. ' Granted, it worked on this one, but I'm only just starting to learn where it's okay to cut corners with aftermarket, versus where OEM is pretty much vital. And electronics seem to be at the top of the list of things you don't cheap out on. Seeing as how a solid 20% of my business is electronics, I can't exactly tell my shops to buy OEM. but at the same time, every time I have one come back 'bad, ' I look back at these videos and wish I could tell them they are making a mistake.
But, they are adults, and if they are willing to gamble their time on a part that may or may not do what they need it to do. I'll keep selling what they are buying.
reply
22: 10 Nice.
I remember doing the counter monkey ASE test, back when I thought that actually meant I knew what I was talking about. Tach drop and a crank no start was always touted as 'replace the crank sensor. ' Granted, it worked on this one, but I'm only just starting to learn where it's okay to cut corners with aftermarket, versus where OEM is pretty much vital. And electronics seem to be at the top of the list of things you don't cheap out on. Seeing as how a solid 20% of my business is electronics, I can't exactly tell my shops to buy OEM. but at the same time, every time I have one come back 'bad, ' I look back at these videos and wish I could tell them they are making a mistake.
But, they are adults, and if they are willing to gamble their time on a part that may or may not do what they need it to do. I'll keep selling what they are buying.
reply
T te
My Matco dealer out in San Diego said he made more money working on Chrysler products than any other line of vehicles (I was working for Ford at the time. I tended to believe him, since he paid cash for his Matco franchise.
I do remember having to replace one of those cats that hung off the exhaust manifold on a Mitsu-shity. I remembered that Chrysler had the same engine and the same exact cat, so I called the Chrysler parts dept, and it was something like 100. 00 cheaper (this was back in 2001/2002. It might have been more, but it sure was fun and annoying to have the Mitsubishi parts guy twist himself into logical pretzels trying to explain that, when they had the same part number.
reply
My Matco dealer out in San Diego said he made more money working on Chrysler products than any other line of vehicles (I was working for Ford at the time. I tended to believe him, since he paid cash for his Matco franchise.
I do remember having to replace one of those cats that hung off the exhaust manifold on a Mitsu-shity. I remembered that Chrysler had the same engine and the same exact cat, so I called the Chrysler parts dept, and it was something like 100. 00 cheaper (this was back in 2001/2002. It might have been more, but it sure was fun and annoying to have the Mitsubishi parts guy twist himself into logical pretzels trying to explain that, when they had the same part number.
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Craig
Being retired but still with a curious mind, I have to wonder if the re-learn fixed the problem or the OEM sensor. But for those that work for a living and for those that need a reliable car to get from point A to point B, I can appreciate your call Eric. I worked on a computer one time where the diagnostic software indicated a certain bad chip. Actually, the chip next to it had a scratch across the top of it which you could see with a magnifying glass and was causing the problem. I'm glad the OEM part worked and the Jeep appears to be fixed and that is what's important. I hope you didn't scratch it on the way in. Thanks for Sharing!
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Being retired but still with a curious mind, I have to wonder if the re-learn fixed the problem or the OEM sensor. But for those that work for a living and for those that need a reliable car to get from point A to point B, I can appreciate your call Eric. I worked on a computer one time where the diagnostic software indicated a certain bad chip. Actually, the chip next to it had a scratch across the top of it which you could see with a magnifying glass and was causing the problem. I'm glad the OEM part worked and the Jeep appears to be fixed and that is what's important. I hope you didn't scratch it on the way in. Thanks for Sharing!
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Ken
The aftermarket sensor could be doing many subtle things that would be hard to pick up from a scope trace. The problem could have happened 200 or so pulses before the ECM outputs reacted to the event. The ECM is obviously the one calling foul and shutting off the ignition, but without more information, it would be difficult to track down the exact event it did not like. However, I am curious if you tried to relearn the chinesium cam sensor. You relearned the OEM one - maybe that fixed it? Probably not, but for completeness, that might have been a step worth trying before removing the old one.
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The aftermarket sensor could be doing many subtle things that would be hard to pick up from a scope trace. The problem could have happened 200 or so pulses before the ECM outputs reacted to the event. The ECM is obviously the one calling foul and shutting off the ignition, but without more information, it would be difficult to track down the exact event it did not like. However, I am curious if you tried to relearn the chinesium cam sensor. You relearned the OEM one - maybe that fixed it? Probably not, but for completeness, that might have been a step worth trying before removing the old one.
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Bolt
A pro tip: if it s a Mopar, you are only allowed to use Champion spark plugs with Mopar crank sensors or you will lose fuel economy, power and have a shaky tach with a poor idle. Also, if Mopar, carry spare crank sensor lol. It s odd that it restarted that quick after the crank sensor got hot enough to stop working. Usually you have to wait 20+ minutes, sorta makes me think it was using the cam sensor to compensate? But then why d it shut off?
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A pro tip: if it s a Mopar, you are only allowed to use Champion spark plugs with Mopar crank sensors or you will lose fuel economy, power and have a shaky tach with a poor idle. Also, if Mopar, carry spare crank sensor lol. It s odd that it restarted that quick after the crank sensor got hot enough to stop working. Usually you have to wait 20+ minutes, sorta makes me think it was using the cam sensor to compensate? But then why d it shut off?
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Tyler
great video! ive seen this this same issue before because of an aftermarket sensor as well! i do have a few questions though. the napa guys will deliver you dealership parts? thats pretty awesome. and is there a reason you used the picoscope over the autel scope? i assume the pico is just easier for people to use? we have one in the shop and i do love to use it. always enjoy a video of yours when the scope comes out!
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great video! ive seen this this same issue before because of an aftermarket sensor as well! i do have a few questions though. the napa guys will deliver you dealership parts? thats pretty awesome. and is there a reason you used the picoscope over the autel scope? i assume the pico is just easier for people to use? we have one in the shop and i do love to use it. always enjoy a video of yours when the scope comes out!
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R.
My 04 WJ was doing this yesterday, decided to scope the CKP, found the body to engine ground laying on the valve cover bolt, evidently from replacing the now leaking valvecover gasket, I tightened, scoped the sensor, signal looked good, no more kicking and bucking. Also, a slight fishbite that she's had since I bought a year ago is gone. Powers and grounds.
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My 04 WJ was doing this yesterday, decided to scope the CKP, found the body to engine ground laying on the valve cover bolt, evidently from replacing the now leaking valvecover gasket, I tightened, scoped the sensor, signal looked good, no more kicking and bucking. Also, a slight fishbite that she's had since I bought a year ago is gone. Powers and grounds.
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Fred
I use to work at Mopar dealership and I can relate because a auto came in after being elsewhere finding an aftermarket parts put in oem and that seemed to repair the problem. At that time the early 80's there were no scan tools that had the capability that you have today basically just a enhanced code reader my 2 cents worth.
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I use to work at Mopar dealership and I can relate because a auto came in after being elsewhere finding an aftermarket parts put in oem and that seemed to repair the problem. At that time the early 80's there were no scan tools that had the capability that you have today basically just a enhanced code reader my 2 cents worth.
reply
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