My car is giving me a code 13 AND code 15. The o2 sensor failure is weird because i just replaced mine a few months ago. I noticed that my idle is a little high and when i try WOT my car hesitates for a second or 2 then starts speeding up. I also noticed when i'm in neutral and i try WOT my RPMs drop to a little less than 500 (sounds like its about to die) for a second then it revs like normal. Any ideas or what i should do to fix it? My car was running somewhat like this earlier this week. I checked out the big tube on the other side of the engine that goes from the intake to the valve cover and it was out. I put it back in and it was running perfect...until i tried to leave work yesterday and it started acting like this. I really wanna get this fixed before the races on saturday so any help would be great. Thanks guys!

Code 13
Oxygen Sensor Failure
When the ECM detects there's no variation in the voltage sent by the Oxygen Sensor during normal operation of the car, it wil set Code 13. Usually this means the sensor is disconnected or it needs to be replaced. Also check for a sticking or misadjusted Throttle Position Sensor.

Code 15
Coolant Sensor (high voltage)
Because the Coolant Sensor never has an infinitely high resistance, the measured voltage should always be lower than the reference voltage. If the measured voltage is the same as the reference voltage, a problem exists with the Coolant Sensor. The ECM will set this code when it detects a problem with the Coolant Sensor (or when the coolant temperature actually drops below -30°C/-22°F).

What brand o2 did you get? I've had a couple new ones crap out. Get the delco or denso

Easiest way to find out whats wrong bro. If you have a laptop/can borrow one, make yourself an aldl cable and check the readouts on all your sensors. It's simpllllle

http://couleefiero.tripod.com/ALDL.htm

i'm pretty sure its a bosch. I've tried the ALDL thing and it didnt workout so well. Maybe i just need a little more instruction. I'll check out the link-Thanks a lot.

ok so i figured it out. I just realized how "honest" our cars are. When the code 15 came up i should have looked at the coolant sensor in the first place...it came out. Put it back in and the car is running normal. The ALDL still won't be a bad idea.