P0135
P0135 has nothing to do with lean condition. What you measured is the return signal that goes back to the PCM. The PCM is telling you that there is something wrong with the heater circuit.
Reference: OBD-II Trouble Code: P0135 Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor1)
Oxygen O2 Sensor Heater Circuit Malfunction 1, Sensor 1)
What does that mean?
This code refers to the front oxygen sensor on Bank 1. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0135.
Symptoms
You will likely notice poor fuel economy and the illumination of the MIL.
Causes
A code P0135 may mean that one or more of the following has happened:
- O2 Heater element resistance is high
- Internal short or open in the heater element
- O2 heater circuit wiring high resistance
- open or short to ground in the wiring harness
Possible Solutions
- short or open or high resistance in wiring harness or harness
- Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)
P0131
P0131 has nothing to do with a lean condition as well. The PCM is telling you that the something is wrong with the signal circuit back to the PCM. This would explain why the signal that you measured is wrong.
Reference: OBD-II Trouble Code: P0131 Oxygen O2 Sensor Low Voltage (Bank1, Sensor1)
Oxygen O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)
What does that mean?
Essentially the same as P0136 and P0137, a P0131 code refers to the first oxygen sensor on Bank 1. P0131 means the O2 oxygen sensor's remained low for longer than 2 minutes. This, is interpreted by the ECM as a low voltage condition and sets the MIL. Bank 1 Sensor 1 is located in front of the catalytic converter.
Symptoms
There may be no visible symptoms to the driver, other than the MIL (Check Engine / Service Engine Soon) illumination.
Causes
A code P0131 may mean that one or more of the following has happened:
- Faulty o2 oxygen sensor
- Short to voltage on O2 signal circuit
- High resistance or open on O2 signal circuit
Possible Solutions
- Replace faulty sensor
- short, open, or high resistance on o2 signal circuit
