99 4Runner, 3.4 Auto Trans, 4x4. I have Factory EWD's.

No changes, work or electrical additions to the truck. Just started happening.

Trans shifts normally, dash indicator lights work and show correct gear. OD button works as does the Norm/Power button.

Headlight switch works normally as does Hi/Low beams and turn signals.

With the key on, trans in park, the park light indicator on dash is lit. As it should be.

When you shift to other positions, the other corresponding indicators on the dash change and follow the gear shifter. All positions work normally. Key on or driving.

Here's the weird part. With low beams turned on, the indicator light on the dash dims. With the high beams it dims almost completely.

Here's the REAL WEIRD PART. The trans will be in drive and the drive indicator light is lit. Driving along fine, flash the Hi beams and the trans will down shift, the drive indicator will go out and the reverse indicator will light. The high beam indicator bulb lights but seems dim.

It still does it when lights are off and flashing the high beams. So the low beams affect it as far as dimming dash bulbs but, the high beam flash REALLY screws it up.

I'm lost! Both circuits by themselves do what they are supposed to do. They SHOULD NOT be connected. But together they cause a major problem.

Only common thing I found is the ground. I think it was IE on the schematic. It looked good but I cleaned it and all other ground points and reconnected them.

The truck is torn apart right now so I can check wiring. I have checked a lot of connections and headlight/taillight sockets, verified grounds.......

Any ideas?

 

Fixed it!!!! Checked every ground and connection in the dang truck. Inside and out.

Found an open in the printed circuit on the back of the combination meter. All the indicator bulbs had a common ground.

The socket for the bulb for the Drive indicator light had no continuity on the ground side. Yet the bulb worked? It did have continuity to a connector so it MUST have found ground somewhere down the line. The high beam bulb had the same ultimate ground so this maybe where the two circuits got crossed up?

Just for the heck of it I put a jumper wire to the ground side of the bulb to the ground side of the bulb next to it. All other bulbs had a common ground so why not.

Stuck the combination meter (instrument cluster) back in and everything works as it should.

Now I have to put the interior back together.

We found several dead end posts on different forums with this exact problem. VERY frustrating! Hope this helps someone else.

 

Thanks for posting the solution

 

As a 99Ltd owner I'm curious if your truck fell under the gas gauge TSB which included the replacement of the computer board behind the combination meter, mine was burnt up pretty bad upon replacement of it and the sending unit as per TSB for my early 99 MFG Date 10/98 was your issue caused by this board or was it a connection near it or not related. If you have a pic of the problem area that may help others in the future.