PO135 Diagnostic and Fix for 2004 Jeep Wrangler - Code Won't Clear
I own a 2004 Jeep with a persistent PO135 diagnostic code that won't clear, even after replacing three front manifold oxygen sensors, the thermostat, and still failing inspection. I'm now at a loss as to what might be causing this issue. While I've ruled out a blown fuse, I suspect there may be an underlying wiring or sensor circuit problem. The vehicle appears to function normally, but the code remains active—this is preventing it from passing emissions testing. Any insights into potential root causes would be greatly appreciated.
Check for a wiring short in either the oxygen sensor circuit or the heater circuit of the O2 sensor. A short can trigger the PO135 code and prevent it from clearing even after replacing sensors.