This morning I started the car (2009 Acura TL SH-AWD TECH), let it run for a few minutes as it was F$#%$ cold this morning (-20 C). Started driving, 2 minutes in to the drive the check engine light came on saying "check emission system" and "check transmission"

Just scanned the code and it reads "P0848 Transmission fluid pressure sensor/switch B circuit high"





Any ideas what this means?

Also I noticed on the highway cruising it seemed like the engine was revving higher than usual, as if it never shifted into the last, 5th gear. Going around 110 kms/hr and the engine was at ~3,000 rpm...

 

Clear the codes and see if it happens again. It could be just intermittent. Warm it up before drive. A tranny oil change may help. To really debug this tho you need the Honda diagnostic tablet to see the behavior of the 3rd pressure switch. Alternatively drive in 3rd gear (in S) with up shifts to 4th and back to 3rd and see if it happens again, fully warmed up. If it does its either the 3rd pressure switch stuck in the off position or your tranny is pretty much toasted.

 

I cleared the code, went for a long drive and didn't happen again. Shifted fine in all gears... Weird, must of been the cold. Tranny toasted? lol I hope not, considering it only has 100,000 kms...

Also noticed a whinning noise at a certain, low speed (only when the car is cold) could be propellar shaft?

 

I guess its nothing, too cold as you say. It may be worth it to drain and re-fill the tranny, just in case. To be on the 100% safe side, it may be worth it to go to a dealer (hopefully some dealer with a good reputation) to take a look at the code memory and see if there is anything else logged. Tell them what happened and see if perhaps they can help. I am sure they'll recommend a tranny drain+refill.

For the prop shaft, as I recall it did whine at all kinds of speeds, especially when the hanging bearing got a bit hot. So doubt that is it. Again, it may be worth it to go to a dealer to look at it, I think you are still covered with the warranty at 100k kms.

 

If it states "B circuit" it's possible there is an "A circuit" which the ECU could be using to operate the trans. Someone has posted, in another thread, the service manual for the 09-10 models which has detailed procedures to follow to diagnose/correct the error.

I agree with Tonyware, a fluid drain/fill might help.

 

Called the dealer to book appointment, told them about the error code and they said they'll replace the 3rd gear pressure switch under warranty (which is the error code P0848) and they said they will take a look at the prop shaft and bearings underneath the car to see if something is making noise . They will do a fluid flush 3x3 as well.

I must say I'm really impressed by the quality of service. Will post back results. Thanks for the responses.