2006 e320 cdi. 150k. Was driving it around 2 years before i parked it in my back yard, covered. Yea i know, less than ideal.

When i was driving it around 2 years ago i was having sporatic issues with it not going into park. I replaced my batteries and the brake light switch. Seemed to go away.

Fastforward to a month ago. I started to get the car ready to go again. Unfortunately needed new batteries, and i think i popped a brake line, the SBC is going nuts). I evicted the mouse nest under the aux battery and under the engine cover. Hosed everything down, checked connectiins. Started in less than 3 seconds like it was never put to sleep 2 years ago.

Moved it foreward out of the ruts. Let it run for a bit, cleaned and rebuilt the trunk from links. I have a 2006 e350 parts car.

Would not go back into park again! Fuuuuuu.... disassembled console, pushed the button, put into park. Cleared out all codes from sitting. No errors but rear SAM and the SBC. No trans errors, no shifter errors. Sill wont go into park. Lil research said common issues, bad module. Fine. Ripped apart parts car as i drove it into the spot and i knew it all worked perfect.

Installed the shifter, now it wont leave park, but will shift back to park when you use the button to go from park to drive etc. All gears work, and returns to park, just wont leave park.

Ok maybe this shifter went bad. Ordered another used one. Same issue. Ok maybe the brake light switch is bad, cheap enough. Replaced with aftermarket and oem, still wont.

The only thing is i dont hear the familier click releasing the shifter when i put the brakes on.

Will a popped brake line, or sbc errors prevent the shifter from leaving park?

Im ripping out whats left of my hair. I have the factory service manual but i cant decifer where to start.

Help with some diag steps?

-- power up batteries with a charger or running engine

-- connect a compatible scanner to read all faults codes

-- Post the code description you need help with.

If you still have no relevant code go read live data to confirm the shifter activities are registered.

Your idea about the bad SBC disabling shifter is a good lead... try too locate relevant live data status.
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when you installed the new shifter, the exact position of the module/shifter is critical (ask how I know!!). Move it back/ford/left/right just a little will made big different on whether you will be able to shift in/out. When I bought my car, 2 of the bolts that hold the module in place were lose, so I removed the whole module to clean up. Upon reinstalled, I was not able to move out/in the park...etc. Had to play with the module position for hours before getting it right!!

If you have STAR/Xentry, you can monitor the status of the brake light switch. Two internal switches in that piece. One switch controls the rear brake lights via the rear Sam and the second switch is used to release the shifter lock.