For those of you who have been here a long time, I apologize for posting yet another XYZ thread but I've got some questions relating to these seemingly common errors. My truck is a 2004 HSE with 136k on the clock. The M+S Lights that I specifically am receiving dont seem to be related to the XYZ switch but maybe voltage as some others have suggested. I've tried to diagnose things as best I can but could use some additional guidance if anyone feels up for doing so.

1. New Battery (AGM Odyssey Extreme) Group 34.
2. Not so new Alternator.
3. While the truck is off, and the battery is attached, the battery is putting off about 12.6v I assume just because there are things drawing on the battery even though the truck is off.
4. When the truck is on and idling in park, I am pulling 14.5v from the Battery, and also 14.5 from the alternator so I think we are good on those two things.

Visually speaking, from the contacts I can see that aren't buried further back into the engine bay, they seem good, not corroded, and clean. The contacts themselves that are attached to the battery are also pretty clean. Lets move on to shifting.

1. If I move "FAST" and change from Park all the way down to 1, no lights occur. I can climb the tree every step, 1,2,3,D,N,P and things are displaying correctly on the dash. No lights. Reverse however.........................
2. If I move from P to R "slowly" or really just allow the truck to idle too long on Reverse while the brake is on, then the lights come on.
3. If I run the truck around town, without lights, park... whatever... and then put it into reverse but don't take my time and simply hit the gas when I hit reverse, then the lights do not come on. But if I repeat the process, drive back into a parking spot, park, change to reverse and take a moment to check mirrors or really just anything for that additional second or so, the lights come on.

My only assumption on this is that when the truck is set into reverse, and those revs drop ever so slightly, which drops voltage for that split-second, that its enough to trip these lights. I don't know it there is a threshold that someone has verified as having these things kick on but I seem to be good on voltage all around as people have suggested things be 13.5 and up (I'm at 14.5). I have not checked the transmission ECU under the seat but will do so next. In the meantime, any additional thoughts on what I might be missing? At this point I do not think it is the XYZ switch, but I'm new here.

 

Not voltage with those numbers, most likely a bad contact in the XYZ switch it just takes a bit of corrosion

 

Is there any preventative maintenance to keep XYZ switch from failing ??