Honda Pilot - Honda Pilot Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 ·
Want to first thank all the members for posting about transmission sensor issues/fixes.... it has been a big help. I've found a lot of information about the P0847 and P0848 CEL codes (3rd gear sensor stuck open/closed) but I have an odd situation that's giving me fits. Thanks in advance for any help or tips.

We have a 2012 Pilot EX-L with about 97k miles. Been a solid vehicle overall. Last December (2019) it threw a CEL with code P0847. Driving fine, no issues, so I drained and filled transmission (it was about due for service anyway), cleared the code and it was good for a year. This last December (2020) it came back, P0847, so I bought the OEM 3rd gear sensor, replaced it, cleared the code and good to go. We live in Texas so it's not winter-weather related but occurring in December it would appear to be temperature related, or just coincidence.

Welp, that lasted about a month and another CEL last week, this time it's P0848 which I interpret to mean the same sensor. It seems like the possibilities are:

1) I got a bad sensor
2) Something is wrong with the connector or harness
3) Something is wrong with the transmission (not the sensor)

It's driving like a champ. I tend to think it's #2 as it's a single wire with no strain relief going into a large connector. When I replaced the sensor I cleaned it with contact cleaner and applied a little dielectric grease but there were no signs of corrosion. Also no obvious signs of damage or being loose. I hate the idea of taking it to the dealer but I've about exhausted my DIY skills on this. Does anyone know what the voltage should be at the connector? Any way to test (ohm?) the sensor to tell if that's the issue? The connector/wire is obviously part of a harness so replacing that is an option but I can only imagine the cost, with no guarantee that's the culprit. Thanks in advance!!
 

·
Registered
Joined
·
9,383 Posts
Are you dealing with the wire connector being oily? I use CRC Electronic Cleaner to spray these if needed. Let dry thoroughly.
But from there, ya, it's a short in the wire or bad switch.
Will not talk about the type of ATF. 😜
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
2,254 Posts
General comment: Dielectric grease is an insulator, not a conductor. Using it on the connectors makes negative sense, except maybe on an o-ring or silicone sealing boot and only then if you don't believe that the seal will work dry. Clean the connections again as Nail Grease recommends, reassemble clean and dry.
 

·
Registered
Joined
·
139 Posts
Does anyone know what the voltage should be at the connector? Any way to test (ohm?) the sensor to tell if that's the issue? The connector/wire is obviously part of a harness so replacing that is an option but I can only imagine the cost, with no guarantee that's the culprit. Thanks in advance!!
In 09-10 Pilot FSM

P0847 - short in 3rd clutch trans fluid pressure switch or circuit
P0848 - open in 3rd clutch trans fluid pressure switch or circuit

At the switch connector, one pin, let say x, connects to PCM via C connector. The other pin, say y, connects to ground. When key is on II, without 3rd clutch fluid pressure, pin x should read 5 volt. With 3rd clutch fluid pressure, pin x should read 0 volt (ground). No mention of ohm test. Switch turns on when pressure reaches 140 psi.
 

·
Registered
Joined
·
866 Posts
Dielectric grease can be (is recommended to be) used directly on electrical contacts to seal around the contact patch of mating contacts. It reduces contact fretting by wear, oxidation and of course arc over. While Auto OEM's still use it on certain connectors, manufacturing a connector or socket contained grease is messy, messy for assemblers, and in automotive and industrial applications the grease may get contaminated during periodic service routines, so OEM's appear to use o-ring or booted connectors, where possible. In years past many plug wire boots were plump with dialectic grease. The aftermarket wire kits came with dielctric grease, and instructed you to squirt it in the boots, as I recall.

Dieletric grease used to be very common on PCM connections, as they needed to be ultra-reliable and the connectors were rarely disturbed for the life of the vehicle. Common in marine applications as well.

Very common to see dielectric grease on the contacts of rotating or sliding controls; audio mixing consoles, vernier knobs, etc.

As for conductivity; contact pressure mitigates the film resistance of the dielectric grease, and it reduces the insertion and contact pressure required to make a low resistance, reliable connection.


And something to ponder, if oil/grease would prevent electrical contact, how do non-sealed connectors inside many transmissions make electrical contact while submerged in trans fluid.... :)
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
9,383 Posts
Dielectric grease can be (is recommended to be) used directly on electrical contacts to seal around the contact patch of mating contacts. It reduces contact fretting by wear, oxidation and of course arc over. While Auto OEM's still use it on certain connectors, manufacturing a connector or socket contained grease is messy, messy for assemblers, and in automotive and industrial applications the grease may get contaminated during periodic service routines, so OEM's appear to use o-ring or booted connectors, where possible. In years past many plug wire boots were plump with dialectic grease. The aftermarket wire kits came with dielctric grease, and instructed you to squirt it in the boots, as I recall.

Dieletric grease used to be very common on PCM connections, as they needed to be ultra-reliable and the connectors were rarely disturbed for the life of the vehicle. Common in marine applications as well.

Very common to see dielectric grease on the contacts of rotating or sliding controls; audio mixing consoles, vernier knobs, etc.

As for conductivity; contact pressure mitigates the film resistance of the dielectric grease, and it reduces the insertion and contact pressure required to make a low resistance, reliable connection.


And something to ponder, if oil/grease would prevent electrical contact, how do non-sealed connectors inside many transmissions make electrical contact while submerged in trans fluid.... :)
So it is established that dielectric grease is an insulator. These conections were not filled with this insulator, from the factory. Is there a chance the dielectric grease is preventing the conection? I'd clean them dry with CRC Electronic Cleaner and see.
 
  • Like
Reactions: aloogatr

·
Registered
Joined
·
9,383 Posts
I would say it's fluid and temperature related. What ATF do you use?
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
139 Posts
We have a 2012 Pilot EX-L with about 97k miles. Been a solid vehicle overall. Last December (2019) it threw a CEL with code P0847. Driving fine, no issues, so I drained and filled transmission (it was about due for service anyway), cleared the code and it was good for a year. This last December (2020) it came back, P0847, so I bought the OEM 3rd gear sensor, replaced it, cleared the code and good to go. We live in Texas so it's not winter-weather related but occurring in December it would appear to be temperature related, or just coincidence.
We have a 2012 Pilot EX-L with about 97k miles. Been a solid vehicle overall. Last December (2019) it threw a CEL with code P0847. Driving fine, no issues, so I drained and filled transmission (it was about due for service anyway), cleared the code and it was good for a year. This last December (2020) it came back, P0847, so I bought the OEM 3rd gear sensor, replaced it, cleared the code and good to go. We live in Texas so it's not winter-weather related but occurring in December it would appear to be temperature related, or just coincidence.
?
 

·
Registered
Joined
·
866 Posts
The OP disappeared? Wondering if cleaning the "insulating" grease from the connector fixed his problem? Pin fitment? Green crusties? Rat nibblings? Sold the truck?
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
3 Posts
Discussion Starter · #12 ·
Thanks everyone for the replies. Very much appreciated. Sorry for the delay in the Paul Harvey end-of-the-story...We were the (un)lucky recipients of a crazy winter storm here in Texas, the fallout from which put this project on the back burner for the past 5 weeks.

Points taken on the dielectric grease. True that it's not a conductor but I don't view it as an insulator, either. Regardless, I cleaned both the connector and the sensor socket with spray electrical terminal cleaner (CRC I think), wiped everything down, visual inspection for no corrosion, and put it back together. Cleared the code and it would be OK for a few miles then back to the CEL, flashing "Drive" light and P0848. Pretty frustrating.

As for the fluid, it's factory Honda purchased at the dealership, serviced about a year/8k miles ago. The fluid level and appearance was fine, and it drives and shifts perfect. I had reached the end of my DIY mechanic abilities so we took it to a local shop (non-dealer) who has worked on it before.

Verdict: The shop owner/main mechanic called me when it was on the lift and he picked my brain about what I had tried thus far. He said in his decades of experience working on Pilots he was convinced it was a faulty sensor and not an actual transmission problem. I could tell he didn't want to ruffle any feathers replacing the sensor that I just replaced myself but I trust him completely and told him if he thought that's what it was, go for it. So he did, factory Honda 3rd clutch sensor, and that fixed it. He also ohm'ed out the wire/connector and said it was good.

In retrospect, and at the risk of stating the obvious, the factory 3rd sensor failed. As for the sensor I installed, it could have been bad. Could have been a fake. Maybe user error. At any rate it's fixed and back to normal operation. I wish I had some magic fix to share with the forum but maybe this thread will help someone with a similar issue in the future.
 

·
Registered
Joined
·
866 Posts
Some parts (even OEM ones on the dealer shelf) are BOOB'ed - Bad Out of Box. Your mechanic was correct on following his troubleshooting and experience; in this case low risk as he didn't have to tear anything down to prove himself or you right or wrong.
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
9,383 Posts
Thanks everyone for the replies. Very much appreciated. Sorry for the delay in the Paul Harvey end-of-the-story...We were the (un)lucky recipients of a crazy winter storm here in Texas, the fallout from which put this project on the back burner for the past 5 weeks.

Points taken on the dielectric grease. True that it's not a conductor but I don't view it as an insulator, either. Regardless, I cleaned both the connector and the sensor socket with spray electrical terminal cleaner (CRC I think), wiped everything down, visual inspection for no corrosion, and put it back together. Cleared the code and it would be OK for a few miles then back to the CEL, flashing "Drive" light and P0848. Pretty frustrating.

As for the fluid, it's factory Honda purchased at the dealership, serviced about a year/8k miles ago. The fluid level and appearance was fine, and it drives and shifts perfect. I had reached the end of my DIY mechanic abilities so we took it to a local shop (non-dealer) who has worked on it before.

Verdict: The shop owner/main mechanic called me when it was on the lift and he picked my brain about what I had tried thus far. He said in his decades of experience working on Pilots he was convinced it was a faulty sensor and not an actual transmission problem. I could tell he didn't want to ruffle any feathers replacing the sensor that I just replaced myself but I trust him completely and told him if he thought that's what it was, go for it. So he did, factory Honda 3rd clutch sensor, and that fixed it. He also ohm'ed out the wire/connector and said it was good.

In retrospect, and at the risk of stating the obvious, the factory 3rd sensor failed. As for the sensor I installed, it could have been bad. Could have been a fake. Maybe user error. At any rate it's fixed and back to normal operation. I wish I had some magic fix to share with the forum but maybe this thread will help someone with a similar issue in the future.
Thanks for the update.
My recommendation would be to change the fluid to Full Synthetic Valvoline MaxLife ATF. It works better in the extreme cold you experienced and is better at withstanding the Texas heat. It does what it says on the back of the bottle. I believe that the transmission fluid had everything to do with your issue.
 
  • Like
Reactions: Matt_P

·
Registered
Joined
·
3 Posts
Discussion Starter · #15 · (Edited)
Thanks for the update.
My recommendation would be to change the fluid to Full Synthetic Valvoline MaxLife ATF. It works better in the extreme cold you experienced and is better at withstanding the Texas heat. It does what it says on the back of the bottle. I believe that the transmission fluid had everything to do with your issue.
I appreciate the recommendation. I'll sure try it out. 🙌
 
1 - 15 of 15 Posts
Top