Truck Fault Code P0136

 Understanding BS6 Vehicles' Fault Code P0136: Causes, Solutions, and Wiring Diagram

Introduction to BS6 Emission Norms:

The Bharat Stage VI (BS6) emission norms were implemented in India starting from April 1, 2020. These stringent regulations aim to significantly reduce the pollution levels caused by vehicles, especially those powered by diesel and petrol engines. BS6 vehicles are equipped with advanced sensors and emission control systems to monitor and manage the engine's performance and ensure compliance with these standards. One critical part of the emission control system is the Oxygen (O2) sensors, which help maintain the optimal air-fuel mixture in the engine. When issues arise, fault codes like P0136 are triggered.

What is Fault Code P0136?

OBD-II Trouble Code P0136: The fault code P0136 indicates that the powertrain control module (PCM) has detected a malfunction in the oxygen (O2) sensor circuit for Bank 1, Sensor 2. This sensor is located downstream of the catalytic converter and measures the oxygen content in the exhaust gases after they have passed through the converter.

What Does This Sensor Do?

The O2 sensor plays a vital role in ensuring that the engine is running at its most efficient state. It helps the engine maintain the correct air-fuel mixture, which is crucial for optimal combustion, fuel efficiency, and low emissions.

What Does “Bank 1, Sensor 2” Mean?

"Bank 1" refers to the side of the engine where cylinder 1 is located. In V-type engines, there are typically two banks (Bank 1 and Bank 2).

"Sensor 2" indicates that the sensor is positioned after the catalytic converter.

Symptoms of P0136:

1. Check Engine Light (CEL): The most common symptom of P0136 is the activation of the check engine light.

2. Increased Fuel Consumption: A faulty O2 sensor can cause incorrect air-fuel mixture, leading to higher fuel usage.

3. Poor Engine Performance: You may notice rough idling, hesitation during acceleration, or stalling.

4. Emission Test Failure: Since this sensor monitors emissions, a failure could cause the vehicle to emit more pollutants and fail emission tests.

Causes of Fault Code P0136:

There are several potential causes of the P0136 fault code in BS6 vehicles. These include:

1. Faulty Oxygen Sensor (Bank 1, Sensor 2): Over time, the O2 sensor can degrade due to contamination or wear and tear, leading to inaccurate readings.

2. Damaged Wiring or Connectors: Corroded or broken wires or connectors leading to the O2 sensor can interrupt the signal between the sensor and the PCM.

3. Exhaust Leaks: Any leaks in the exhaust system, particularly near the O2 sensor, can cause the sensor to give incorrect readings.

4. Catalytic Converter Issues: A failing catalytic converter can affect the performance of the downstream O2 sensor.

5. PCM Software Issues: In rare cases, a glitch in the powertrain control module's software can cause erroneous sensor readings.

6. Contamination: Fuel additives, engine oil, or coolant can contaminate the O2 sensor and impair its function.

How to Diagnose and Fix P0136:

1. Use an OBD-II Scanner:

The first step is to connect an OBD-II scanner to the vehicle’s diagnostic port and confirm the presence of the P0136 code. Check for any additional codes, which might provide more clues to the underlying issue.

2. Perform a Visual Inspection:

Inspect the O2 sensor’s wiring and connectors. Look for signs of corrosion, damage, or loose connections.

Check for any exhaust leaks that could be affecting the sensor’s performance.

3. Test the O2 Sensor:

Using a multimeter, test the voltage of the oxygen sensor’s output to ensure it’s within the correct range. If the readings are outside the expected parameters, the sensor may be faulty and require replacement.

4. Inspect the Catalytic Converter:

A failing catalytic converter can lead to incorrect readings from the downstream O2 sensor. If you suspect this, perform a backpressure test to assess the converter’s condition.

5. Check for PCM Updates:

In some cases, a software update may be required for the PCM. Check with the vehicle manufacturer for any technical service bulletins (TSBs) related to this issue.

Example of P0136 Fault Code Fix:

Vehicle: BS6 Ashok Leyland Dost+ Symptom: Check engine light on, with rough idling and increased fuel consumption. Diagnosis Process:

1. Scanned the vehicle’s OBD-II system and confirmed the presence of fault code P0136.

2. Performed a visual inspection and found that the O2 sensor’s wiring was damaged due to heat exposure.

3. Replaced the damaged wiring harness and inspected the O2 sensor, which showed signs of contamination.

4. Replaced the O2 sensor (Bank 1, Sensor 2) and cleared the fault codes using the OBD-II scanner.

5. Test drove the vehicle to ensure proper operation, and the check engine light did not return.

Wiring Diagram for P0136: Oxygen Sensor Circuit

Here’s a simplified wiring diagram to help understand the oxygen sensor circuit associated with fault code P0136.

+12V Battery Power

               |

               |-----------|

               |           |   

       +-------|           |----------+------(Ground)

       |       ECU/PCM     |          |

       |                   |          |

   O2 Sensor Heater    O2 Sensor Signal   O2 Sensor Ground

  (Bank 1, Sensor 2)   (Bank 1, Sensor 2)  (Bank 1, Sensor 2)

      +-------------------+----------------+

Explanation of Wiring:

1. Power Supply: The O2 sensor’s heater circuit receives 12V from the battery, controlled by the PCM.

2. O2 Sensor Signal: This wire transmits the sensor’s readings to the PCM, which monitors the voltage to determine the oxygen content in the exhaust gases.

3. Ground: The sensor is grounded through a dedicated wire to complete the circuit.

Conclusion:

Fault code P0136 in BS6 vehicles can lead to reduced engine performance and higher emissions if not addressed promptly. It is usually triggered by issues with the O2 sensor located downstream of the catalytic converter. A proper diagnosis, including a visual inspection and sensor testing, is crucial in fixing the issue. In many cases, replacing the O2 sensor or repairing damaged wiring will resolve the problem. Regular maintenance and monitoring of the vehicle's emission system can help prevent such issues from arising in the future.