420A Car shutting off. P0134 and P1294

[princesstori0417]

I have a 1997 Mitsubishi Eclipse GS. I just recently had a problem of my car not starting, figured out it was the anti theft feature. It now starts and runs for about 5-10 minutes before it shuts off again. I have 2 codes, P0134 and P1294. Any recommendations for what I should try? I have already replaced the battery, spark plugs, wires, and coil pack.

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[luv2rallye]

P0134 says your upstream O2 sensor is not working properly. This tells what the air/fuel mix is to which the ECU then adjusts fuel mixture. It's critical to be working properly.

 

[BLACK'98DSM]

Yep I would start with the front O2. Sounds like it dies during the open loop/closed loop transition.