DEAR CAR TALK: I had my 2000 Cadillac Escalade towed to the mechanic, and he determined that my battery needed to be replaced. After the new battery was installed, I was informed that the “4-wheel” light on the dash was constantly on, and that the mechanic could not determine the cause.

He referred me to a dealership that specializes in Cadillacs. When I mentioned to the mechanic there that my vehicle had been hitched from the rear and towed approximately 15 miles riding on the front wheels, he suggested that that could be the cause of the light not turning off, because the vehicle should have been transported riding on top of the tow truck bed rather than being towed with the front wheels on the ground.

Could this actually be the cause of the light constantly being on, or could it be a module that needs replacing? – Henry

RAY: The dealer is right that all-wheel-drive cars are never supposed to be towed from one end on a hook – they always should be flat-bedded. Any non-knuckleheaded tow truck driver would know that.

So it’s possible that the towing did do some serious damage. But before you conclude that, there are a lot of other – and much cheaper – things to check.

The first thing I’d check is the switch. There’s a push-button switch on your dashboard that selects between 2WD and 4WD modes. You can try replacing that yourself for about $50. If the light goes off, go out and buy a lottery ticket, because it’s your lucky day, Henry.

If it’s not the switch, you really need to have the car’s computer scanned for stored faults. For instance, a scan could reveal that it’s a faulty solenoid, a failed transfer case actuator motor or a bad computer.

Or, as I said earlier, you could have lunched the center differential when you got towed. That’s thousands of dollars. In that case, you probably could just apply the “black tape solution” to the light and drive the car until it drops. A car that’s old enough to vote is hardly worth putting a new all-wheel-drive transmission in.

If the differential is cooked, the towing took place recently and you know who towed you, you can try making a claim against them in small claims court – if they haven’t closed up shop and fled to Saskatchewan.

That’s assuming you didn’t tow it yourself, Henry, or give the driver permission to tow it on the front wheels because there was no flat bed available and you really wanted to get home in time to watch “60 Minutes.” I’ll cross my fingers for a bad switch for you.

Got a question about cars? Email Car Talk’s Ray Magliozzi by visiting the Car Talk website, www.cartalk.com.