08-05-09, 02:28 AM
i have a 97 deville. two separate codes come up through the diagnostic center P0135 and P0300. One is the oxygen sensor and the other is a cylinder misfire. I need help with fixing it myself. what do i do? If it reads oxygen sensor heater circuit malfunction what do i replace or do to fix it? For the random/multiple cylinder misfire, any feedback on what it could possibly be. :banghead:
08-05-09, 09:37 AM
Stop shouting !!! We all can read this text as-is.
P0300, for your 97, may well be caused by spark plug wires, plugs, or coil(s). Remove the engine beauty cover and, at night, mist the plug wires with water from a spray bottle. Any arcs and sparks ?? New plug wire and coil cleaning time. When was the last time you can positively identify a plug and wire change ??? Over about 80,000 miles/6 years and you're on borrowed time. Look at your car in www.rockauto.com. You'll want an ACDelco wire set (~$105) and 8 ACDelco #41-950 Platinum plugs. While you're in there, remove the ICM/coil pack and clean everything, connectors and all. Use the diagrams to replace the plug wires - the wire connections to the coils is very important.
The O2 sensor code says "circuit", so you're in the wiring and connector troubleshoot business. (You need to identify which (of your 3 or 4) O2 sensor is setting the code.) The sensor diagrams may not be exactly the same as your engine, but they give you a place to start.