Error Code P0050 is referring to a problem in Heated Oxygen Sensor (HO2S) Heater Control Circuit Bank 2 Sensor 1. The PCM triggers this code when it detects open or shorted to ground condition on the HO2S (Heated Oxygen Sensor) heater circuit.

Definition

For the vehicle’s engine to run properly there should be an accurate ratio of fuel and air, which should be at 14.7:1 (fuel to air). To ensure this ratio, the engine’s PCM (Powertrain Control Module) depends on the HO2S which works to detect the oxygen level in the exhaust.

HO2S which is sometimes referred simply as O2S or Oxygen Sensors, need to reach a specified minimum operating temperature (750˚ F) to be able to product the right voltage signal. The faster the HO2S reaches that temperature, the faster it is for the sensor to start sending the right signal for the PCM (or ECM). The PCM also uses the information sent by the sensor to adjust the fuel deliver to the engine.

To achieve the accurate temperature, a heater element is incorporated within the HO2S. The PCM controls this heater element by allowing current flow to ground, based on the engine load and the signals from the engine coolant temperature. This also shortens the time needed for the engine to achieve closed loop, which ultimately decreases emissions.

On other vehicles, the oxygen sensor heater receives 12V fused supply voltage, as well as computer controlled ground. This supply voltage is sent to the heater as long as the key is in position. The PCM activates the heater under certain conditions by completing the ground to the O2 sensor heater.

For other vehicles, the oxygen sensor is supplied with a computer controlled 12V feed and continuous ground. And if the PCM detects trouble from the Bank 2, sensor 1 heater circuit, it will trigger the same error code.

Error Code P0050 refers to the Bank 2, the side bank of the cylinders without the cylinder #1. This code is identical to P0030, but on Bank 1.

Common Symptoms

Besides the activation of the Check Engine light, the most obvious symptom for this error code is the prolonged time needed for the engine to achieve closed loop. And as with most error codes that concerns the HO2S, this code decreases fuel mileage, while also causing the engine to run rough.

Possible Causes

There are many reasons for this error code to appear, but its most common trigger is when water gets inside the HO2S connector, causing its sensor to blow. Other possible causes include:

  • Damage or failure of Bank 2, sensor 1
  • Damaged or failed HO2S heater circuit element
  • Open or short in wiring
  • Open on oxygen sensor heater ground circuit
  • Open or short on oxygen sensor heater B+ battery feed (for control circuit for some vehicles)
  • Failed PCM (rare)

How to Check

Qualified mechanics diagnose this code by installing a scanner into the DTC port. After confirming the error code with clearing, road test and re-tests, mechanics perform a thorough visual inspection of the sensor’s wiring.

They will then observe the data from the sensor to check for proper operation.

Mechanics also inspect the PCM and perform the specific tests supplied by the vehicle’s manufacturer.

How to Fix

This error code is usually a wiring issue, thus, it is important to conduct a thorough visual inspection for the wiring and connectors that concerns the heated oxygen sensor and its heater element. Repair any damages on the wiring that connects with the exhaust. If the HO2S is damaged, then it should be replaced.

If visual inspection shows no obvious signs of the problem, and the scan datastream confirms the problem in the Bank 2, Sensor 1 heater element, as it pulls 0 amps, then there must be an open in the circuit. Check for any blown fuses and then disconnect the oxygen sensor connector.

With engine off, and key on, check for 12V fused battery feed in the heater element using the voltmeter. If you see no voltage, then repair open or short in the B+ feed circuit. Make sure you replace any blown fuse from the short. If the B+ battery feed is undamaged, then remove PCM wiring connector of the ground (control) circuit and check for resistance on the circuit. If you see infinite resistance, then you need to repair the open in the circuit. If control circuit checks out, then there’s a good chance there’s a problem on the oxygen sensor. Replace the O2 sensor and re-test.

You need to conduct thorough diagnostic testing before replacing the sensor, or it won’t solve the error code. Thus, if you’re not confident with your engine-repair skills, take your car to your dealer or have your vehicle checked by a qualified mechanic.