Modern Vespa

I am replacing the cracked exhaust manifold on my GTS250. I unplugged the Lambda sensor and as carefully as possible removed it from the broken pipe.

Some of the soot on the cylindrical portion, just above the threads was disturbed from handling.

If the sensor was functioning properly before removal, do I just install it into the new manifold and hook everything back up, or is now the time to replace as a best practice?

Ive also read they sometimes do not appreciate being removed.

The bike has about 15K on the clock and I believe a sensor went bad around 6K and this is the replacement.

Photo of said sensor.

Thanks in advance!

Just reinstall it, and you will be just fine.. We only replace them when they fail, (not that often to be honest)

Remember the golden rule: If ain't broken don't fix it! 8)

It's also not too difficult to replace - so why not wait until it fails.

How do you know when it fails? Can it be bad and not cause a check engine light?

IMHO, if it's not triggering the Check Engine light, it doesn't need to be replaced.

(Okay, I once melted the connector on one when I forgot to plug it back in after reinstalling the exhaust -- but I zip-tied the connectors together and it continued to work for years afterwards).

Lambda sensors last a very long time. Typically by mileage on the GTS you can be looking at an average 50-60k miles or more. Although I've known them to continue functioning for 70-80.000 miles on bikes that we looked after. Manufacturers will tell you 40k is the typical lifetime limit. This is due to the erosion of the lambda tip, and or the failure of the heating elements on 4 wire systems. If you ride WOT they wear out more quickly.

Ultimately, it's a variable thing but yours should be fine for many more miles yet!

Bypass it and break the warning light, also reprogram the ECU to not notice the operation of the probe ..?

My check engine light is on and I suspect the lambda sensor. Is there a way to test it to be sure?

2006 GTS with 40k miles on it.

You'd need a diagnostic tool to read the code. Shade-tree technique is just to swap it with a known-good one and see if the problem goes away, then you know.

You can test the lambda with a multimeter. Full test specs for impedance listed in the free workshop manual in this site's Wiki.

Yes, you can do that but you need tech & know how to do it. It's also not the best idea & will affect the fuel economy, emissions & the performance. Trust me I've done it on numerous engines for experimental purposes (when developing engines) to problem solve.

Here in Italy it is done on some diesel cars (not all) with the particulate filter, they exclude the probe and bypass the filter.
The aim is less maintenance and an increase in power. Obviously it is illegal and if you are discovered there are high fines and even the seizure of the car, moreover in the event of a road accident the car is considered unsuitable for circulation on the road.