I had my trans replaced 2 weeks ago and they said the bank 1 and bank2 O2 sensors were bad. I have a 99 3.8L how many and whereare they i saw one on the front exhaust manifold.

Hi
You should find 4. Two upstream - one in each exhaust manifold just downstream of the head, and two downstream - visible from underneath just after the catalytic converters. As I recall, bank 1 is the rear 1 - 3 -5 and bank two is the front.

thanks i will change them and see how it runs after.

Hi wrenchturner

If you do not have an OBDII scanner, get autozone or someone similar to read the "check engine" code for you so you change the right ones. Also, I have had one of my O2 sensors register a "slow response" code before. I cleared it with my reader and it did not return. Point being - you might want to get an independent verification before you pony up for new sensors.

Good luck