2017 Isuzu MU-X Pricing and Specs

This needs to be sorted out quickly as a car that you can't be sure is in Park is always a potential to roll away on its own causing who knows what grief and damage. It sounds like there's something amiss with the way the gear selector is talking to the actual transmission, and any resistance in the action of the shifter really shouldn't be there. That said, you do need to have your foot on the brake to select a gear from Park, so maybe you're taking your foot off the brake pedal prematurely.

You're possibly correct that the two issues are related as a car that thinks it's not in Park, will probably not want to allow you to use the walk-away locking mode. But here's the good news: This is absolutely a warranty issue and Isuzu needs to fix it at its cost.

Book the car in to be inspected as soon as possible and, in the meantime, make sure it's parked somewhere from which it can't roll away. Physically chocking a wheel (with a house-brick, a rock or whatever) isn't a bad idea till it's fixed, either.

This sounds like a case of low transmission fluid. Check the transmission dipstick according to the instructions in the owner's manual to see if the level is where it should be. Low fluid level can cause all sort of problems from slipping to a lack of drive to uneven shifts and shifts occurring when they shouldn't. Also, try to find out what fluid was put in the transmission when it was last serviced. The wrong type or grade of fluid can cause the same types of problems as not enough fluid.

If the fluid checks out, then you need to start looking at other causes such as glitches in the on-board computer that controls the driveline. An electronic scan of the vehicle would be the next step.

It sounds very much like the transmission is confused electronically or has a problem with its valve body which is supposed – in conjunction with the computer – to make decisions about what gear the transmission should be in. Perhaps it's as simple as a dodgy electrical connection somewhere and the impact of potholes or buffeting from passing trucks is causing a short-circuit somewhere.

The first piece of advice, however, is to not drive the vehicle any farther. You not only risk damaging the transmission, but it's also dangerous to drive a vehicle that might suddenly select the wrong gear at random. The second piece of advice would be to take the vehicle to a dealership and have its computer scanned to see if any fault codes have been recorded. If your local dealer doesn't want to know, take it straight to head office and contact Isuzu's customer service division.

The good news is that your vehicle is still under the factory warranty, so make it Isuzu's problem, not yours. Just make sure that the behaviour has been logged as a problem, at which point it's classed as a pre-existing condition and Isuzu is still obliged to fix it even if the warranty runs out.