oxygen heater circut malfunction

P0135 indicates a fault in the cylinder bank #1, O2 sensor #1 heater circuit. Check for 12 volts and ground when the engine's running cold. the heater won't be on all the time so you need to see it on sometimes. If not, look for a fault in the wiring or the connector at Bank 1 Senosr 1 circuiut.