Grab some coffee...

Over the past year, I've had flashing M and S lamps or Three Amigos. Mostly this happened when it was cold and wet and after I shifted gears. These problems went away over the Spring and most of the summer. I never had both at the same time.

A few weeks ago the M and S lamp came back along with a SRS light. It also put the tranny into limp home mode. The fault code was for the neutral safety switch. Again, it happened after I shifted from Park to Drive or vise versa.

I posted on the board and the consenus was to change the battery. Alternator voltage was around 14V under all conditions, so it seems fine.

After sitting in my garage for two weeks, today I installed the biggest honking battery I could get at Autozone. Voltage around 12.6 off the shelf.

So, I clear any codes and fire it up for the first time in a few weeks.

I immediately get the 3 amigos!!!!! And when I shift the tranny the M and S lamps come back along with the SRS. Clearing the codes and restarting yields the same result.

For what it's worth, I also noticed that when I shift gears, not all lights are illuminated on the shifter. Neither the R nor any of the D1-D3 lamps come on. I also see the P light illuminating while going through the other gears some times.

The problem sounds like it really is the neutral safety switch, but what about it could also cause my 3 amigos?

 

The only way they could be related is if the SLABS unit were going south, it controls most things on the truck.
I have no idea where to check or what you would do from here.
The neutral safety switch would only not let you shift out of park, the XYZ switch is a separate switch.

 

Thought they were one and the same...good to know.

I'll try to take it off this weekend and look for lose wires and corrosion. Hopefully there will be something obvious.

 

Unplug it and clean the connections with electrical contact cleaner, then plug it back in.
People have had problems with the transmission temp warning light coming on from a loose/dirty connection, this may be a similar problem.

 

Mike, Spike, or anyone else...

I removed the two bolts that mounted the XYZ switch to the tranny and then removed the nut that mounts the shifter cable to the "cog" coming through the XYZ switch. I pried a bit trying to get the bracket out, but was unable to.

Anyway, on a hunch, I started the truck and shifted gears. Viola!! No problems. No flashing lamps and the illuminating lamps on the selector all worked.

Thinking that I "adjusted" what was broke, I put everything back together.

I restarted the truck and the flashing "m" and "s" came back.

What gives? Think maybe the cable is just out of adjustment? Was something bound up inside the switch and ungalled when it wasn't mounted?

Sorry for the idiot questions, but I'm not the mechanical sort.