Switching sensor signals

I'm looking for suggestions. I have a 0-5v sensor on my car. Most of the time, this signal is fine and I just want to pass the signal through without disruption. I'd like to use the arduino to monitor other conditions on the car and occasionally substitute my own analogWrite signal for the original sensor signal. I'm looking for a chip/approach that let's me switch between the original signal and the one I generate with analogWrite.

I've rather keep the original signal in place and not go through an adc-dac round trip in order to occasionally modify it, so hoping someone can point me in the right direction for a fast digital throw switch. Thanks!

I'm looking for a chip/approach that let's me switch between the original signal and the one I generate with analogWrite.

Such a chip is an analog multiplexer, if you're googleing for it you'll find lots of types and configurations.

occasionally substitute my own analogWrite signal for the original sensor signal.

analogWrite() doesn't produce an analog signal (despite the name) but a PWM signal. You need a circuit (like an R-C circuit) to produce a real analog signal out of it.

Multiplexer -- thanks. The ones I've seen before switch 8 or more lines at a time -- do they come as single line switchers?

Understood about pwm and RC filter -- no problem.

4053 - triple one into two switch

Thanks. Was just looking at 4051B which seems to do all I need... Thanks all.