Hi - New to the site......2009 MDX showing single code - "P0842" via Chk Eng Lite, and occasional "flashing D".... Seems to drive fine

Code = Transmission Fluid Pressure Sensor/ Switch A Circuit………

Only noticeable driving symptom is Trans will occasionally get stuck in 3rd, won't grab 4th, high RPMs... Stop vehicle, key cycle, drives fine again

If I understand correctly, this vehicle has 3 separate AT pressure switches:
1 down low & 2 up high

I think I incorrectly diagnosed - I purchased new switch from dealer (Item 12 on Acura diagram, Part: 28610-RAY-003 but package stated Part: 28610-RKE-004... I'm sure its a valid x-ref, so I changed the lower switch only, drove great for a while but symptoms / lights reoccurred. So I will change the upper. Do I change both or only 1 up top? which ones? Access under battery tray?

Advice please - Thanks!

 

Anyone? Wife's car - She's threatening to take to the dealer.......

 

P0842 - 2nd clutch transmission fluid pressure switch (short or stuck ON)

The 2nd gear switch is the one on the top left of the trans:

 

Part No 11 here, make sure to get a new washer as well.
AT SENSOR - SOLENOID for 2009 Acura MDX

While you are changing switches, I'd highly advise you change out the 3rd gear switch too as it controls 3rd and 5th gear. That's the one you ordered Part no 12 (for 3rd gear). Acura updated the part so it's got a new number hence why you got something different. That switch is on the bottom and can be done without removing a bunch of stuff. I simply pulled back the driver fenderwell and was able to get a deep socket onto the sensor with a 12" extension on my torque wrench. Make sure you have deep sockets as the sensor + connector is too tall to sit in standard sockets.

Here's the guide for 3rd gear switch:

 

If replacing the switch doesn't solve the issue, you may have a bad wiring situation:

 

Thanks for the response and info..... Gonna dive back into shortly

 

Hello,

I am having a similar problem and hoping to piggy back off this.

About 8 months ago the problems began, trans getting stuck in gear, can't pull away from a stop, from Drive to Park, Park to Drive and I am good to go.

Difference with my case is the radio resets constantly, usually while downshifting.

Dealer replaced the 4th gear sensor. Okay for a month. So then I replaced the 3rd sensor. Problems never really went away again. Transmission doesn't show too many problems but the radio is forever restarting while I drive. About 2 or 3 times a day I will have the quickly throw it in Park and back to Drive.

Should I just replace the 2nd gear sensor? Where did you get the code? I am not seeing any codes like that.

Thanks

 

This sounds like a deeper electrical function short / issue - might be better addressed by some of the core experts on this forum.

Specific to your question, I initially received my single code (while driving) on the message center (Navi Info Screen), along with Orange Engine Symbol "in dash" aka CEL, and occasional flashing "D" - Gear position indicator. Additionally, I used an OBD Analyzer to confirm / clear the code.

No radio symptoms, only mechanical, in that vehicle would not shift out of 3rd... For short term remedy, I would stop vehicle completely, pull keys out of ignition, and restart,..... problems / code ceased temporarily until I could replace sensors.... All fine now.

Might be some value in resetting the ECM? / PCM - power control module equivalent for Acura... I can tackle the easy elec issues, but most are not in my wheelhouse...

 

As stated above it sounds like you have a larger electrical issue. The only way the car could get stuck in gear is if the solenoid or valve is sticking for a gear or if the computer is giving the incorrect signal to cause it.

Look for moisture damage near the ECU/PCM and also the radio. I would also look for any damaged wiring in the vicinity.