I own a 1999 Mazda Protege with a 1.6L DOHC engine. The check engine light is illuminated, and the diagnostic tool reads trouble code P114-1. This code indicates a fault in the heater circuit of the downstream oxygen (O2) sensor on bank 1. I'm looking for clear guidance on how to diagnose and resolve this issue effectively without unnecessary repairs.
Thanks for the input, Jeff. I replaced the downstream O2 sensor, and the check engine light cleared. However, I now experience a sudden surge when accelerating—like the car 'lunges' forward. This suggests fuel delivery issues. Could this be related to the Throttle Position Sensor (TPS)? I haven't seen any new error codes from the ECU. Any advice would be greatly appreciated.
When you describe 'lunging' forward, does it feel like idle surging or fluctuating? Cleaning the Mass Air Flow (MAF) sensor is a good starting point—clogged or dirty MAFs can cause incorrect air intake readings. Also, some older Mazda Proteges have exposed ECU units under the cup holder that may get moisture ingress over time. Check for water damage and ensure proper sealing. Please update if you find any issues.
The car runs smoothly when first started, but after a few minutes, it begins to surge during acceleration and idle becomes rough. I'm experiencing power loss and erratic behavior. I'll follow your suggestion and clean the MAF sensor as soon as possible. Thanks for the tip, Chuck.
Jeff—after investigating further, I found a crack in the air intake hose while checking the throttle body. The leak allowed excess air into the engine, causing incorrect air-fuel ratios and resulting in surging and poor acceleration. Replacing the hose resolved both the surge and the P1141 issue. Thanks for your help, Chuck.
Hey Chuck, I'm having the same symptoms—after spending $500 on EGR valve and O2 sensor replacements, my check engine light came back with P1141. The mechanic mentioned a broken air intake hose, but I haven't noticed any performance issues yet. Could this be the root cause? Any advice would be much appreciated. Also, where can I find an affordable replacement for the air intake hose?
P1141 is a diagnostic trouble code (DTC) indicating a heater circuit fault in the downstream O2 sensor on bank 1. The most common fix is replacing the downstream oxygen sensor, as this component often fails over time and can cause misfires or poor fuel efficiency.