Ok so my A3 that i bought on a limb has 4 error codes. It is a 1.6 1998. I looked in the section for help but it was not coming up. So the codes are 00537 Oxygen Sensor Control 00557 (no code found in the manual) 00525 02 Sensor - Voltage Low - G39 00668 Battery Power Voltage Supply (terminal 3) So does this mean i must replace the Lambda Sensor (i am guessing there is only one in the front downpipe) It is idling a bit rough and is stalling VERY easily. Any help or advice or help would be greatly appreciated. Remember i am a relative noob so idiot speak would be preferred!