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CEL frenzy, after driving through standing water

8047 Views 11 Replies 5 Participants Last post by  subiesailor
New to I have 2010 Outback 3.6 and 2017 Legacy 3.6. Outback is my swiss army knife and has weathered blizzards, hurricanes and nor-easters without a single issue till now.

Reading forum about Engine, Cruise, Brake Christmas Tree effect on forum. I had to run through a 4-5" of standing LI Sound water with Outback today after NorEaster and started getting the Christmas tree light effect. AGM Battery 1 mo old and gas cap tight so those are not issues. Car was running rough after passing through water and the idiot lights came on. Checked air box and battery cables and everything is fine. Car has since "dried out" and engine seems to be running fine.

Has anyone had similar issues after running through standing water? Unfortunately, passing thru standing water from storms is getting to be a regular fact of life where I live on Long Island and won't be able to avoid it. That is reason why I have Outback and leave wife's Legacy in driveway under such conditions. Just as precaution I will go to Autozone for computer check. I hope its not O2 sensors...
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You get the lightshow because Subaru made a design decision to make a big lightshow as an attention-getter, starting with the 2010 models. Too many people were simply ignoring the lone check-engine light.

The car is illuminating the check-engine light (and thus all the others) because there are a lot of sensors below your self-imposed waterline. Not all of them are waterproof, and in some cases they simply can't work underwater. Example- a catalytic converter simply cannot maintain normal operating temperature when submerged. There isn't enough waste heat to sustain the reaction when it is cooled by water from the outside. So even without water intrusion into the electrical system, the car is being pushed outside its normal operating parameters and it's completely fair to expect a diagnostic reaction. It's just annoying because the display behavior has been cranked up.

It's theoretically possible that they could put yet another sensor under there to determine if the car was in deep water, then use its data to suppress the other warnings. But that isn't something available off-the-shelf in modern automotive management systems, and Subaru's price targets demand high usage of off-the-shelf technology.
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