Volkswagen Forum - VW Forums for Volkwagen enthusiasts

Okay there are a few possible problems. I too was getting a code which threw the engine light on. I had it read at autozone and it came up as (bad Cat). I replaced the Cat and the codes were cleared since i had the battery disconnect so that i could do the required welding ( so i did not short anything out ) . All was okay for a day and the light came on again. I then referred to the SMALL leak i had from the intake manifold to the cat connection. Before i fixed that i changed the thermostat as well as temp sensor ( sometimes if the thermostat is not letting the car heat up or the sensor is bad it will assume the car should be warm already when its really not throwing the code for the O2 sensor up) so after those two fixes i repaired the exhaust leak and I have not had a code come on since ( 2 weeks ). I am running the same motor and car only a 2001. Also check your battery strength with a tester. Sometimes in a newer cars ( sounds absolutely crazy ) if the battery is not at optimal strength it will send false readings. The CAT or temp sensor/ thermostat is more than likely the culprit. It only took me a few hours to change the cat and sensor/thermo. Also what temp are you running at ? After warming up the car should rise to 189-190 and stay there without moving. If it moves or runs cooler and the needle fluctuates indicating the temp is going up and down..... replace that thermostat and temp sensor immediately. If the car is not running 189-190 after running for a bit and staying there you can damage the motor over a shortened period of time. GOOD LUCK hope all goes well and you can resolve your issue. Any questions ask for sure !