Sensor Failure

[TruckerTim]

Took the day off yesterday to spend on the boat and wound up spending the day, (temp 96) on the dock.

Idled out of the marina and 300 yards out in to the channel alarm beeping starts. Check the Volvo head and see "sensor failure" and nothing else. Shut her down and dropped anchor. turned the key back on and beeping starts again but now water temp is showing 210. Still only showing "Sensor failure".

Raise the engine cover and nothing disconnected and yes, the Quick Drain is in the closed position. Jumped in the water and checked the water intake. Nothing clogged. Called the marina, (they're a Cobalt dealer as well) and explain. Tells me manifold sensors go bad all the time and that's probably the only issue but to bring it is and have them check it. So I wait till engine temp drops to 175, (20 mins) and start idling back to the dock. Temp gets to 200 and shut down, drop anchor... repeat.

Finally make it to the dock, (55 mins later) and tech meets me there. He determines one sensor is bad but also tells me Volvo put out a service bulletin in late 2018 about a batch of sensors for these that were bad and should have been replaced. Apparently mine never were. Four hrs later and four new sensors later I head back out in the channel. At the exact same spot as earlier, beeping starts, sensor failure showing and engine temp jumps from 160 to 205 in one second. Call tech back and idle back on. (30 mins this time to get in.)

He starts it up and temp is back to 160 but still beeping and sensor failure showing. He hooks up his laptop to it and all shows ok. He and I idle back out... All good. Get it up to 3500 rpm's.... All good. I ask him why if all the sensors were replaced and everything on the computer looks good why was it showing sensor failure and engine temp high... His response- " it just works that way sometimes..."

Run the boat for the rest of the afternoon, (2hrs) and all good. No beeping, engine temp at 160 and no sensor failure codes.

A few questions- Any others seeing these sensor failures? Others having multiple sensors go out at the same time??

Understand these guys were GREAT! They dropped everything and jumped on my boat. And it's not the dealer I bought from, just where I store in the late summer and early fall. So I don't fault them for the "It just works that way" comment, but just find it odd that after changing all four sensors I get the same failure code, then after hooking it up the the computer all is fixed.

[AsLan7]

He starts it up and temp is back to 160 but still beeping and sensor failure showing. He hooks up his laptop to it and all shows ok. He and I idle back out... All good. Get it up to 3500 rpm's.... All good.

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So the second time you brought the boat back as indicated above, what did the tech do to solve the problem so it won't come back? ( You only indicated "it and all shows ok")

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[TruckerTim]

He didn't do anything other than hook his laptop up to it and restarted the motor. (I have that backwards above. Hooked up the laptop, then started the motor.) That's part of my issue. Just because we swapped out four sensors, is that rally the problem, given I had the same issues after the swap out?

I'm loosing count of days lost and the number of warranty issues I've had in the 14 months of ownership! This is the fist Volvo issue, but still....