Engine Light Never Stays Off

I have a 2003 Hyundia Elantra with 70,000 miles on it. The enigine light came on and it was "determined" by Pep Boys that 2 sensors needed to be replaced-- oxygen sensor bank 1 and ambient temp sensor. A day later the light came back on. It was then determined that they needed to use a different type of sensor that was "intergrated". That was done but the light came back on once again. I took it some where else and it was "determined" a new cat converter was needed. I was assured the light would not come back on after this was replaced. It was replaced and 10 minutes after leaving and paying $700, the engine light is back on again. Anyone know why the engine light keeps coming back on? I'd be willing to bet I never needed the sensors or the cat coverter and it's some malfunction of the engine light and that I'm being scammed.

You need a True Diagnostic Trouble code (DTC)!
Don't leave it to the 3-stooges to analyze your problem, find a retired Mechanic working at AutoZone 1st.

It could be as simple as an old battery, causing bad codes.

If the Catalytic converter was bad, see www.catalyticconverterwarehouse.com (http://www.catalyticconverterwarehouse.com)

Thanks. The cat converter was replaced and the engine light came on 10 minutes after leaving the shop. I'll be taking it to autozone tomorrow to get a diagnostic code then back to the shop.

I'd like to know what the codes were... as well did they replace the Bank 1 O2 sensor?