I have 2006 scion xb and when driving the rpm stays around3500-4000 when running 65 mph can it be modified to run lower rpm

That is a mess and points to nothing in particular, perhaps a communication issue with the BCM?

You need an auto electrician with a professional grade $5,000 scan tool computer with access to wiring data and the ability to read wiring diagrams.

https://www.google.com/search?q=auto+electrician+near+me

https://fuse-box.info/scion/scion-xb-2004-2006-fuses-and-relay

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scan it , it will tell you why.
if TBW fails throttle by wire fails speed is like 20mph max or less. on purpose., so scan it.
also if RPM is low foot ******* the throttle.?
then engine power lacks, scan it.
if RPM goes way high but MPH not same increase,the transmission is dead or slipping.

Here's a link. Check the Belts 2004 2006 Scion xB 2005 Scion xB 1 5L 4 Cyl Here's a picture layout William. 2005 Scion XB Drive belt replacement

I know you are looking to have the remote starter run a third time but I would say you need to look at your Fuel Pressure Regulator on the Scion. Sounds like it is not holding fuel pressure at the fuel rail and that is why it requires a third Crank

I would say you have a problem with the steering part of car, have a mechanic look at it

Fyi....I know this post is several years old but if my answer can help someone it's worth it. I took my car to the dealership today for literally this EXACT problem on my 2010 Scion xB with 125k miles. I read this post and was shocked to read that someone else's xB was behaving the same way under the same conditions. In 4th gear at around 38 MPH and 1500 RPMs I get a vibration and a noise that, like the OP said, sounds like you're going over a rumble strip. That's the perfect wat to describe it. The dealership told me that it needs a torque converter. They want to charge me a thousand for the part and another thousand for labor because they've got to take the whole transmission out of the car and it's going to take 2 days (really 9 hours, they said, but they'd be keeping the car 2 days). I'm currently calling around to see if ANYONE can do it cheaper, but just in case anyone else comes here looking for an answer to this question, I hope this helps. Torque converter might be your problem.

yes and no most warenties cover the engine and drive train, but with it being this new i still would take it back to the dealer to see if it is covered

SOUND LIKE WATER GOT IN THE LOWER FRONT ELECTRICAL SYSTEM WHERE BATTERY IS LOCATED.

No....the rpms differ from engine to engine and from manufacturer to manufacturer. RPM's are always higher at higher speeds.

Hi,If your car have more than 50 k miles ,try oxigen sensor...