Strange dealer diagnosis

[ASUMTNEER]

My in-laws have a 2004 V8, 4WD SR5 with roughly 170k miles on it. The truck recently started throwing the abs, brake, vsc and trac control lights as well as beeping at them. It would go away after they shut the car down for a while. I figured it may be a bad wheel speed sensor, but wasn't sure.
They took it to the toyota dealer today and their diagnosis was a bad belt tensioner. This doesn't make any sense to me. They did say they got a bit of a squeel on cold starts, so maybe the tensioner is bad, but I wouldn't think it would be related to those lights coming on.

Any thoughts? The dealer has ordered the part and they will get that replaced next week.

 

[BlackWorksInc]

That sounds weird to me, not sure why the belt tensioner would affect the ABS system...

 

[ASUMTNEER]

They claim since there isn't enough tension, the belt is slipping and not turning the water pump at times. Therefore causing a sensor to misread and throwing the lights. I would think if this were the case it would throw a cel and not abs, etc.

 

[lightfreak]

I found a thread with the same problem regarding belt tensioner triggering the Xmas tree lights on the dash.

http://www.toyota-4runner.org/4th-g...sc-trac-check-engine-light-after-offroad.html

 

[Cruiserfanatic]

They claim since there isn't enough tension, the belt is slipping and not turning the water pump at times. Therefore causing a sensor to misread and throwing the lights. I would think if this were the case it would throw a cel and not abs, etc.

Whoever this dealer is, it sounds like they don't have a clue. The V8 water pumps are timing belt driven, and if that belt was losing tension at all, it would jump time. The water pump is very low resistance compared to the cams. It sounds to me like they found the belt tensioner while trying to diagnose the ABS issue, but the service writer is getting his info mixed up, or is trying to bullshit his way through a sale. As far as the ABS and VSC, if the light is on, there should be a code. Did they tell you what the code was? I have a 2003, and the zero point calibration needs to be performed from time to time, especially if the vehicle is started with a low battery (sounds strange I know). Also, the other day, my VSC kicked on while I was on a freeway entrance roundabout and my left front tire was a little low on air. Obviously was enough to kick the system on while the left front tire was taking a lot of the vehicle weight while I was on the roundabout, but no lights stayed on. These systems are incredibly smart, so whatever issue you are having, should have some kind of code or direction for diagnosis. Not just throwing weird parts at it.

 

[Cruiserfanatic]

I found a thread with the same problem regarding belt tensioner triggering the Xmas tree lights on the dash.

http://www.toyota-4runner.org/4th-g...sc-trac-check-engine-light-after-offroad.html

I think these are 2 different issues. In your link, whatever they did, it set a check engine light, which also kicks the ABS and VSC lights on. In this complaint, only the ABS and VSC lights are on and the vehicle keeps beeping at them, which is the VSC system kicking on. I personally have never seen a serpentine belt tensioner cause a check engine light, but that doesn't mean it can't happen.