The code P0135 means O2 sensor heater circuit malfunction bank 1 sensor 1. This means you most likely have a bad O2 sensor. The possible causes are:
- Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit open shorted to ground
- Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit poor electrical connection
- Faulty Engine Control Module (ECM)
Usually the code indicates a bad Oxygen sensor, but an intake vacuum leak or a failing fuel pump can cause the code, so check your intake vacuum hose for a leak or hole. But most likely, you have a faulty Oxygen sensor. Now Bank 1 Sensor 1 means the bad O2 sensor is the one on the number one cylinder side (which is the cylinder closest to the timing belt or where all your belts and pulleys are),which is bank one. If you look really closely, you will see that the number 1 cylinder is just a little bit closer to the belts than the number 2 cylinder. Now that you know which side you are dealing with, the next step is which sensor. There are two O2 sensors on each side (upstream or downstream), four total. Sensor 1 is the upstream sensor, which is before the catalytic converter closest to the exhaust manifold. Number 2 sensor is on or after the catalytic converter. So in short, you are replacing the O2 sensor on the Number 1 cylinder side before the catalytic converter. They are a pain to remove. Get some Pb Blaster lubricating oil and spray on the threads and let sit for 10 minutes and spray it again. You will need a 7/8 Oxygen sensor removal socket to remove it. Don't forget to disconnect negative battery terminal and O2 wire harness first.. Any questions please feel free to email me. Good luck.