I have a really clean 99 coupe with 131k on the odometer that I picked up for $500. It obvioulsy had a few issues when I bought it lol I had to replace the Cam Position Sensor(CPS) plug and for good measure I put the target magnet and CPS form my parts car 98 stratus 2.4 DOHC on the neon. Then it thru bad upstream O2 sensor code 134 sensor staying centered. I trouble shot the system with my DVOM and could never get a straight voltage reading so I replaced the sensor. I tore apart the wiring harness from the ECU plug one and had to replace the O2 return wire. I also replaced the downstream O2 sensor and it is still throwing code 140 after about 10 minutes of cruising. How bad are the wiring harnesses on these cars, this one has had oil on it. Is it possable that I have a wiring issue for the downstream O2 sensor is there another likely culprit. Thanks for any information.

 

So you have looked at the wiring for both sensors correct? No broken or exposed wires? Also, check the fuel pump wire.

 

THanks for the reply but I sold the car as is for about 900 profit last week the guy who bought it said his last neon had the light on for 2 years lol.