Wet sensor can’t send signal to engine

DEAR TOM AND RAY: In January, the water pump went out on my 2001 Dakota (V-6 engine). Everything under the hood got soaked with coolant. I had the water pump and all the hoses replaced, as well as the drive belt. Now when there is very foggy or damp weather and the truck has been sitting for a day or more, it won’t start. After a few hours, when the temperature rises a bit and the air moisture is reduced, it will start and run fine. Is there a sensor that will cut the engine off if it gets damp? Does the “catalyst system efficiency” have anything to do with this problem? – Bob

RAY: You need to move to where there’s a drought, Bob. Have you considered Death Valley?

TOM: I don’t think your problem has anything to do with your water pump failure or the eruption of Old Faithful under the hood. I think it is a faulty sensor problem.

RAY: My guess would be the crank angle sensor. It’s located on or around the transmission bell housing, which makes it vulnerable to moisture and splashing water.

TOM: As the name implies, the crank angle sensor measures the position and speed of the crankshaft, and sends that information to the car’s computer so that all the elements of combustion in each piston can be timed to happen at the right moment.

RAY: When the crank angle sensor does not send a signal, the car definitely won’t start. Or run.

TOM: You also ask about the catalyst system efficiency, Bob. That tells me that your check-engine light came on, you looked up the trouble code, found out it meant “catalyst system efficiency” and you had no idea what that meant, so you ignored it.

RAY: It means your catalytic converter is failing, Bob. When the converter eventually plugs up completely, it will prevent the car from running at all.

TOM: And it’ll certainly prevent you from passing your state emissions inspection soon, if it hasn’t already.

RAY: So you probably need a crank angle sensor and a catalytic converter, Bob. I’d do the sensor first. That way, you know you’ll be able to start the truck on the day you have an appointment to get the converter replaced.

Got a question about cars? Email Click and Clack by visiting the Car Talk website at cartalk.com.