Snapper s200xt. mower nearly dies and eventually does when pulling pto switch. engine backfires, sputters out, etc. Runs fine w/o pto engaged.

It sounds like you have covered most of the possible issues with the electrical system. A ground issue could be a possibility, but there are other potential causes as well. Here are a few more things to check:

1. Check the wiring, connections, and terminals for the PTO. Verify that there are no loose or corroded connections and no damaged wiring.

2. Inspect the PTO clutch for wear, damage, or signs of shorting. A failing clutch can cause an increased electrical load, which can drain the battery and cause the engine to stall.

3. Check the belt tension and condition for the mower deck. A loose or worn belt can cause excessive load on the PTO and engine, leading to stalling.

Float may need adjusting .

bad need of a tuneup? like new spark plugs, ?
172 , is 02 rich/ lean warning. this one is low oxy for rich.
this code can just be a victim. for sure , with misfire.
means 02 sensor stuck at rich,
what is water temp in engine coolant, at failure? less than 150F?
could be lots of things.
leaking injectors, bad fuel.
injector sticking> causing misfire.
id use a scan tool and watch all sensor when it fails.
too high fuel pressure.
misfires cold, but only luke warm cold starts not fully cold.

just one DTC, no P0300 or 30x misfire codes, not even P0300 pendings?

DIRTY INJECTORS OR SPARK PLUGS FOULED OUT.

Sounds like your culprit is the fuel pump my friend

You want to check your timing for accuracy and then check all plug wires for burned or cracked ends. Also check the single coil tower where the coilwire connects for very small cracks. Then check the inside of the disrtibutor cap for the same small cracks. Throughout this process I'm certain you'll find the culprit. Thanks, Dana

Have you thought about it possibly being the engine that has something wrong with it? Have you checked the cylinders?

Have the catalitic converter check sounds like it may be clogged. This will cause it to choke off exhaust when it gets hot

Sabre riding mower. Runs, back fires, almost dies,still runs. Back fires again, then dies and can not restart Please HELP!!!!!! Mower model #1438 14.5/38. Engine Briggs and Stratton, Model #287707, 14.5hp, OHV.