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Discussion Starter · #1 · (Edited)
How to: Reverse Sensor replacement; M66 Transmission

Here's a thread with some terrible pictures (click to enlargen) on how to change the reverse sensor on an M66 transmission. It's pretty easy.

Symptoms: You put the car into reverse and the rear white bulbs don't come on. Make sure it's not just a blown bulb by testing or replacing one of them. For me it was intermittent, sometimes I'd have both bulbs, other times neither. You can back into a parking spot in front of a glass wall (like a storefront) and via the rear view mirror, tell if the lights come on or not.

Parts needed: (1) Reverse sensor, I got mine from FCP for $16.75

Tools needed: Hand tools to remove airbox/MAF, hammer and small metal punch to remove the retaining pin, small pry bar to get weighted plate off transmission, small crescent wrench to remove sensor, optional Zip ties, optional bolt if you lose the retaining pin

Time: 1 hour or less

out of 5, due to removal of retaining pin and maneuvering of shifter plate to remove it.


Preamble: With the car off, set the parking brake, open the hood, open beer #1

1. Using a small torx screwdriver, remove the 4 screws holding the air box top half in place. Save the screws and remove the cover.

2. Remove the hex head bolts holding the air box lower half in place, two on the box itself and two on the air guide, save the bolts. If you have an R*Kelly-style intake hose you may need to remove the air filter as well. I did but I have a retaining bolt on my intake hose, some folks don't.

3. With the air guide pulled aside you get remove the final air box bolt. Carefully unclip the MAF sensor wire and undo the worm clamp that attaches the airbox/MAF to the intake. With the clamp undone, tug on the airbox and remove it. Save the screw.

4. Stuff a clean rag into the intake to make sure nothing gets in there. Don't stuff it so far the rag is lost and don't forget to remove the rag before you start the engine next. The circled area indicates the area we'll be working in, the arrow is for the rag.

5. Using your hammer and metal dowel, carefully tap out the retaining pin that's holding the weighted shifter plate to the top of the transmission. Be smart, not like me, and hold onto the pin so once it's freed it doesn't disappear into the inky blackness of night. With the pin removed, use a small pry bar to raise the plate off the transmission along the red line in the photo, it will be tight. Carefully maneuver the weighted plate off the transmission and out of the way. You now have full access to the sensor.

6. On the sensor, remove the wiring clip. Mine just pulled right off. Some SSers use a special socket wrench to remove the sensor as there isn't much room. I just used a small crescent wrench and was able to get a grip on the sensor and remove it. Once out, screw the new one in and pop the wiring clip back on, orientation either doesn't matter or I got lucky. I used the optional zip ties to secure the clip to the sensor. It might just be my 04 but there was nothing for the clip to clip onto, it was only held in place by tension. I used zip ties to go all the way around the top of the transmission, then looped one around the clip itself and tensioned it down. That clip is going nowhere. My sensor had no trace of thread lock. Open beer #2

7. Reassembly is easy unless you lost the retaining pin like I did. I searched through my parts bins until I found a bolt the perfect length and width to fit with no play. It also isn't too big to rub or hit other parts. Reattach the weighted plate and lightly tap it onto the shaft with your hammer, being careful to match up the pin holes. Tap the retaining pin back into place. Remove the rag in the intake and reattach the MAF. Re-bolt the airbox into place, reinstall your air filter if you removed it, re-screw in the airbox top cover and air guides, then reconnect the MAF clip. You did remove the rag, right? You see it on the floor and not still in your intake? Double check. I'll wait.

Testing is easy, just put it into reverse (really just hard to the far right, that'll engage the light) and have a helper check for the light. Make sure you don't disconnect either of the shift cables themselves, or else you'll enjoy the "adjust your shifter cables because now you can't get into 6th" game that I did. Time for beer #3.

Finally, a milestone reached:

3,510 Posts
I know you did this 5 years ago, but what happens when I get to the sensor and nothing is plugged into it? Where would the wires have gone?
They must be there somewhere under the turbo inlet pipe check everywhere.
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