*P0036 – O2 Sensor Control Circuit (Bank 1 Sensor 2).*

✅ P0036-Meaning

Bank 1 Sensor 2 = Downstream oxygen sensor (after catalytic converter)
The ECU is detecting a fault in the O2 sensor heater circuit — usually open, short to ground, or short to power.

The heater helps the sensor reach operating temperature quickly.
If it fails → poor fuel trim feedback, delayed closed loop, possible catalyst issues.

✅ Most common causes 

1. Failed downstream O2 sensor heater element

2. Open circuit in the heater wiring

3. Blown O2 sensor fuse (common)

4. Shorted wiring touching exhaust

5. Poor connector contact / corrosion

6. ECU driver fault (rare)

🔧 Fast diagnostic procedure (step-by-step)

Use a multimeter and wiring diagram.

1. Check the O2 Sensor Heater Fuse

Many vehicles have a dedicated A/F heater or O2 heater fuse in:

Engine bay fuse box

Under-dash fuse box

If blown → replace it and inspect wiring for short to exhaust.

2. Check the Sensor Connector

Remove Bank 1 Sensor 2 connector

Look for:

Burnt pins

Oil/water inside

Broken lock tabs

Repair if needed.

3. Measure Heater Resistance (Sensor Side)

At the sensor pins (usually the two same-color wires are heater):

Normal resistance:
▶️ 5–20 Ω (varies by car)

If resistance = OPEN (∞) → sensor heater is burnt → Replace sensor.

If resistance < 2 Ω → heater shorted → Replace sensor.

4. Check Power Supply to Heater (Car Side)

With key ON:

One heater wire should have battery voltage 12V

The other wire goes to ECU ground driver

If no power:

Check fuse

Check harness continuity

5.Check ECU Driver Ground

Back-probe the heater ground wire.

When engine is running, the ECU pulses the ground (PWM).
If the ECU is not grounding:

Check for open in ground wire to ECU

Rarely the ECU driver is faulty

🔧 Typical fixes

✔ Replace Bank 1 Sensor 2 O2 sensor
✔ Repair heater power wire
✔ Repair sensor ground wire to ECU
✔ Replace blown heater fuse
✔ Repair connector corrosion
✔ Fix melted wires touching exhaust

Welcome to madurai car service 💐🙏🏻.