A/T P light?

All,

My 2002 Tacoma 4WD has one warning light that does not temporarily illuminate when the key is switched on but before it’s started. Normally on any car, all the dash lights will light up with the ignition, and extinguish when it starts.

Given that this single light was the exception, I assumed the bulb was bad, and while having other work done I had the shop open the cluster up to ‘fix’ it.

Turns out the bulb is fine. Swapping it with an adjacent bulb had no effect. The A/T P just doesn’t ever light up. It’s located to the left of the water temp gauge.

So this is the question I should have asked before paying to have the cluster opened: is it SUPPOSED to light up, as I assumed? Or does it just sit there, dark at all times, until a problem with the system arises that then turns it on?

If your light illuminates when the key is turned on, then I have a circuit problem that needs investigating. And if not, then I’m an idiot for not asking here first before paying to have it torn apart.

Please let me know. Thanks!

 

@MatthewMay1 do you know the answer to this?

 

The manual says it's an unengaged "park" indicator. Something about having the transmission in park while the 4x4 selector is in neutral.

Light Should illuminate when shifting between neutral and four low when you're shifting 4x4.

 

Okay, good to know, thanks.

But, the most basic question remains: does it illuminate when you first switch on the key without starting? If the answer is ‘no’ I can have the shop put the cluster back together now.

 

No illumination with power on

 

Interesting. In my truck when I first turn on the key, the battery and oil temp warning lights temporarily illuminate. Why aren’t yours on?

 

No clue. Model difference?

 

I should emphasize that all the other warning lights momentarily illuminate when the key is first turned on, then some go out after a second or so. Battery and oil pressure remain on until it’s started and then all lights are extinguished.

 

Best I can decipher looking at the wiring diagram there is no "bulb check" circuit for it, it should only illuminate if the transmission is in park and the transfer case is in neutral.

 

Allow me to share what I have learned, just in case anybody else is tempted to be incredibly stupid as I was.

First of all, the light works.

But as mentioned above, Toyota engineers inexplicably forgot to include it in the ‘bulb test’ circuit which illuminates all the other dash bulbs when the key is first switched on.

I had never seen this light work, so I didn’t know what it did, and the owners manual is completely opaque about it.

So. IF you have a 4WD and IF you have an automatic transmission, the transfer case cannot be switched between 4H and 4L unless the transmission is placed in neutral. There is also a neutral position in the transfer case.

If you try to move the transfer case from 4H and 4L while the transmission is in anything other than neutral, a lockout switch keeps it from moving. If, however, you put the transmission in neutral, and then place the 4WD transfer case into its own neutral (between 4H and 4L), and then if you subsequently put the transmission into Park, then and only then the warning light will illuminate. I suppose with the transfer case in neutral, the transmission is fully isolated from the downstream drivetrain, so if you put the transmission into park, the truck would still be able to roll freely.

This lesson cost me $150 to learn.

The most important, global lesson is to come here FIRST and ask the questions before throwing money away!

 

What did you spend the $150 on?

 

This is my first automatic transmission (lest my Prius, but that’s not really a car).

I just assumed that was a warning light for “automatic transmission pressure.”

 

Because the light didn’t illuminate briefly with all the other lights when the key was first switched on, I assumed it was a burned-out bulb. I didn’t have time nor desire to tear the dashboard apart myself so I took it to my mechanic. He tore into the dash, swapped bulbs to test and determined the bulb worked fine.

Only then did I think to come here and ask the question. Having received great responses above, I then instructed him to button it all back up. He only charged me for an hour of labor although he said it actually took a bit longer than that.

 

Me too, and because the owners manual fails to properly explain it, I was uncomfortable with the idea that the bulb was burned out and I could suffer an annunciated transmission failure with no annunciation. Hence my unnecessary exploratory dash surgery.