Yaris Low Coolant Temp Problem!

buckaye
Thu, 25 Aug 2011 14:07:28 +0000
Maintenance/Repairs

Hi there all. Before someone says “normal” I know the low temp light is supposed to come on until the car reaches normal operating temp

My problem is really strange and my mechanic and I are both perplexed. I have a 2008 Yaris automatic sedan with 98K miles on it.

The symptoms:

After driving for quite a while (30 minutes or more at times) the low temp light will come on… and sometimes goes right out… and sometimes goes on for a while.

If the check engine light isn’t already on - it will eventually go on.

Sometimes with the low temp light is on - it will race the engine (just straight high rev) OR it will pulse the engine (like I am pumping the gas peddle) OR it will not let the car shift into high gear (rare). Remember… all of this happens after the car has been running for while so it warmed up.

What we’ve tried (over a 4 week period now):

The error code indicates to replace the thermostat - so we’ve replaced it… twice
We’ve replaced the actual low temp sensor
We’ve checked the wiring between the sensors and the computer - wiring does not appear to have a short
Last week we replaced the computer (thank GOD with a used one (200.00)…because the same problem still exists with a replaced computer… a new one would have cost 800 - 900 dollars).

What the mechanic says now:
Might be an air conditioning thing running the fan too long?

Can you really run a fan so long it will drop the car temp back to below the low range operating temperature while driving on a highway? That seems pretty unlikely to me…

Has anyone seen this? Does anyone have any ideas what we should try next? If it were just a flickering light, I wouldn’t be so concerned… but because it revs the engine (even when I am at a stop light and I have to push the brake harder so it won’t start moving) and it sometimes wont shift into high gear… it’s concerning from a safety perspective.

Please Help!

11 posts - 6 participants