A P0136 code relates to the oxygen sensor 2 which lies post the catalytic converter and monitors the catalytic converter for the bank 1 side of the engine.
It gathers voltage readings based on the oxygen level in the exhaust and relays it to the Engine Control Module (ECM), which uses it to regulate your engine’s fuel injection levels.
Whenever the P0136 code appears, the ECM has determined that Sensor 2 located behind your car’s catalytic converter is malfunctioning.
What Does Code p0136 Mean?
Diagnostic trouble code (DTC) P0136 stands for “O2 Sensor Circuit (Bank 1, Sensor 2).” It refers to the same malfunction as the engine code P0137, except it applies to the second O2 sensor on Bank 1.
The P0136 code triggers when the ECM believes that the Bank 1 O2 sensor is not correctly working.
More About p0136 and Lean/Rich Codes
Sensor 2 on the Bank 1 side means that it is located on the side of the engine that contains the #1 cylinder.
The sensor 1 is tasked with reading the amount of oxygen in the exhaust system and then emitting a voltage measurement between 0.1 and 0.9 volts.
It monitors these voltage readings and determines if the exhaust is lean–meaning there is more oxygen than expected–or rich–meaning that there is more fuel than air present.
The ECM then increases or decreases fuel injector pulse width according to the air-to-fuel ratio that is set on the vehicle from the factory.
It sets the P0136 code when the sensor 2 voltage is low for longer than two minutes. The wave form produced by the secondary O2 is much more gradual with a lower frequency bounce between 300 to 750 mv.
The ECM will set codes P0139 or P0140 if it detects a slow response or no response from the O2 sensor, respectively.
The P0138 code is set when the ECM detects a higher-than-average voltage reading (usually about 1.2 volts).
Potential Causes of a p0136 Code
Potential Causes as listed below
- Malfunctioning O2 (oxygen) sensors 2 in Bank 1.
- Exhaust leaks close to O2 sensor 2.
- Open circuit resistance resulting from corroded oxygen sensor connectors.
- Broken or frayed wiring.
- Intake air leakage.
- Shorting O2 sensor signal circuit.
- Faulty PCM.
- Faulty Rear Heated Oxygen Sensor Bank 1
- Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
- Inappropriate fuel pressure
- Faulty fuel injectors
p0136 Code Symptoms
Potential symptoms as listed below:
- Lit check engine light on the dashboard.
- Increased tailpipe emissions.
- Misfiring engine.
- Check Engine Light will illuminate.
- The vehicle may idle or run rough.
- Decrease in fuel economy.
- Engine dies.
- Black smoke out of the exhaust and/or bad-smelling exhaust.
How to Fix p0136 Code?
The following steps will assist you in diagnosing and repairing the root cause of your vehicle’s P0136 diagnostic trouble code.
As always, it is highly advised to consult factory-specific service literature for your particular make and model of vehicle, before attempting any repairs of this type.
Check For Presence of Additional DTCs
Before beginning the diagnostic process, you should carefully check your vehicle for the presence of additional trouble codes, with a quality scan tool. Any fault codes that are found, should be carefully diagnosed and remedied before proceeding.
Carefully Inspect O2 Sensor and Connected Circuit
Begin by Carefully inspecting the corresponding O2 sensor for obvious signs of damage. Likewise, check for any points of concern within the affected O2 sensor’s wiring pigtail/connector.
Analyze Value Fluctuations
With the use of an OBD-II scan tool, analyze feedback from the affected O2 sensor.
In doing so, check to see if these values fluctuate rapidly. If this condition is observed, the O2 sensor itself is likely at fault.
Perform Vacuum Test
With the use of an appropriate vacuum gauge, perform a vacuum leak-down test. Any vacuum leaks uncovered during such testing should be remedied immediately.
Test For Exhaust Leaks
Next, an automotive smoke machine can be plumbed into a vehicle’s exhaust, in a bid to locate any offending exhaust leaks. Any leaks that become evident during this step, should be repaired before proceeding.
Replace Oxygen Sensor
If all the above tests and inspections do not produce verifiable result of your vehicle’s P0136 diagnostic trouble code, the affected O2 sensor is likely at fault. Replace this sensor, clear all diagnostic trouble codes, and take your vehicle for a lengthy test drive to confirm the repair.
How Much Does It Cost to Fix a p0136 Code?
A P0136 code, which indicates an issue with the oxygen sensor circuit (Bank 1, Sensor 2), typically costs between $200 and $500 to fix, with the primary expense being the replacement of the faulty oxygen sensor itself, along with potential labor costs for wiring checks and sensor removal/installation.
- Diagnosis needed: Before replacing the sensor, a mechanic will likely need to diagnose the exact cause of the P0136 code, which could involve checking for damaged wiring or other issues within the sensor circuit.
- Part cost: The oxygen sensor itself can range in price depending on the vehicle make and model, but generally falls within the $200-$300 range.
- Labor cost: A mechanic might charge between $60-$100 for labor to remove and install the new sensor.