2006 Toyota Sienna turn signal & shift interlock

[weebl]

My van has just started a strange behaviour this week. Looking for someone familiar with Toyota electrical systems from this era who might be able to help.

Intermittently, the 4-way flashers will stop functioning. Also, turn signals will intermittently stop functioning, left more so than right.

Now, I also have the completely electric shift interlock refusing to disengage when the vehicle has started and brake pedal pushed in. I can manually override it with the (mechanical) override switch.

These two issues may or may not be related.

I should also note I observed the 4 way flasher behaviour on occasion when the trailer was attached to the vehicle: if the engine was not running, the flashers would work briefly then stop while the trailer was attached. No issues could be found with the wiring at the time, and the vehicle pigtail has since been replaced.

I thought this was possibly a weak battery or alternator problem: the summer I saw the issue when the trailer was attached, I believe my battery was weak and it did have to be replaced that winter. I plugged the smart charger while the vehicle was idling, but it read "full" and refused to charge things further.

Any ideas where I should start?

 

[weebl]

I should add that if the signals are not functioning, I can make the non functioning side(s) do a half flash, but cannot repeat the half flash until at least 2 seconds have passed.

 

[Rolla07]

Probably a bad relay/flasher. Situated under dash.

 

[weebl]

Is there an easy way to test it? If this is the cause, then I'm sure I will also need to track down the shift interlock problem as I can't see a bad relay/flasher causing the shift interlock problem.

 

[Quest]

for intermittent left-side turn signal issue, you'll probably need a new headlight combination switch replacement?

Q.