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HappyCarGuy

Intermittent "dreaded P0021" code

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Posted (edited)

Hey there, folks!

 

I looked into some of the forums, and most people are talking about bad camshaft sensors - to no luck, apparently. So, here is the low-down on the vehicle:

- I just replaced the timing chain on my sister's 2004 (3.5l) Pathfinder. After replacement, the vehicle ran fine during the test run, until about halfway home, wherein it went into limp mode - no CEL. 

- I made it back home, let the car sit for about a half hour, and it was fine. Delivered the vehicle to her, where she drove to work the next day with no issues, until on her way home (about a 20-30 mile highway commute). The car went into limp mode again. She took the car to her main mechanic, where he was unable to replicate the issue, but he checked that all timing was correct (I was a bit afraid that it may have jumped a tooth while the tensioners were building pressure). Keep in mind, this vehicle idles perfectly, and will drive for a few miles now before the it goes into limp mode. No bad clicking, knocking, or 'baddie sounds." We just replaced BOTH VVT solenoids and replaced the oil (again) with a new filter. Still goes into limp mode, and still has the dreaded intermittent P0021 code. My sister, at this point, is ready to just trade the car in (and I would FULLY support getting this gremlin out of her possession). We were going to try a few things, and gather some recommendations before we do so, though. 

 

My next step will be to switch camshaft sensors. If the code now switches to P0011 (I think that is the correct code), I will know that the camshaft sensor is bad. If it doesn't, though, there will be no need to throw more money at it (though it could still be a wiring harness issue). Other than that, I don't exactly know where to begin diagnostics with this. I feel like we have done the majority of 'cheap' fixes to solve the issue. I told her that I am happy to tear back in, and replace the camshaft/and or phaser if need be. I would like to use that as an absolute last resort, though. Is there any way to test that a phaser is going bad? I have noticed tiny fluctuations of RPMS (almost as if the RPM gauge is 'vibrating' for lack of better words?), which makes me think that the sensor is on it's way out, or the sensor is picking up on incorrect magnetic rpms of the phaser. 

 

What do you all think? Any suggestions? 

Edited by HappyCarGuy

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Posted (edited)
3 hours ago, HappyCarGuy said:

Hey there, folks!

 

I looked into some of the forums, and most people are talking about bad camshaft sensors - to no luck, apparently. So, here is the low-down on the vehicle:

- I just replaced the timing chain on my sister's 2004 (3.5l) Pathfinder. After replacement, the vehicle ran fine during the test run, until about halfway home, wherein it went into limp mode - no CEL. 

- I made it back home, let the car sit for about a half hour, and it was fine. Delivered the vehicle to her, where she drove to work the next day with no issues, until on her way home (about a 20-30 mile highway commute). The car went into limp mode again. She took the car to her main mechanic, where he was unable to replicate the issue, but he checked that all timing was correct (I was a bit afraid that it may have jumped a tooth while the tensioners were building pressure). Keep in mind, this vehicle idles perfectly, and will drive for a few miles now before the it goes into limp mode. No bad clicking, knocking, or 'baddie sounds." We just replaced BOTH VVT solenoids and replaced the oil (again) with a new filter. Still goes into limp mode, and still has the dreaded intermittent P0021 code. My sister, at this point, is ready to just trade the car in (and I would FULLY support getting this gremlin out of her possession). We were going to try a few things, and gather some recommendations before we do so, though. 

 

My next step will be to switch camshaft sensors. If the code now switches to P0011 (I think that is the correct code), I will know that the camshaft sensor is bad. If it doesn't, though, there will be no need to throw more money at it (though it could still be a wiring harness issue). Other than that, I don't exactly know where to begin diagnostics with this. I feel like we have done the majority of 'cheap' fixes to solve the issue. I told her that I am happy to tear back in, and replace the camshaft/and or phaser if need be. I would like to use that as an absolute last resort, though. Is there any way to test that a phaser is going bad? I have noticed tiny fluctuations of RPMS (almost as if the RPM gauge is 'vibrating' for lack of better words?), which makes me think that the sensor is on it's way out, or the sensor is picking up on incorrect magnetic rpms of the phaser. 

 

What do you all think? Any suggestions? 

This is a real shot in the dark, but my vehicle has gone into limp mode 3 times in the 9 months that I’ve had it. Each time that’s happened, it’s been on the same day that I do a sloppy change from Reverse to Drive (put it in drive while the car is still rolling back). But at the same time, without fail, if I properly shift the car, it doesn’t go into limp mode. This could have nothing or everything to do with your problem, but it’s my only frame of reference for dealing with this. 

Edited by PathyDude17

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1 hour ago, PathyDude17 said:

This is a real shot in the dark, but my vehicle has gone into limp mode 3 times in the 9 months that I’ve had it. Each time that’s happened, it’s been on the same day that I do a sloppy change from Reverse to Drive (put it in drive while the car is still rolling back). But at the same time, without fail, if I properly shift the car, it doesn’t go into limp mode. This could have nothing or everything to do with your problem, but it’s my only frame of reference for dealing with this. 

Have you had any codes pop up when this happens? Or does it just go into limp and then no other issues?

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Posted (edited)
6 hours ago, HappyCarGuy said:

Have you had any codes pop up when this happens? Or does it just go into limp and then no other issues?

Never checked codes, limp always goes away on its one with no other issues

Edited by PathyDude17

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