Technical Definition:

O2 Circuit (Bank 2, Sensor 2)

Technical Description:

The o2 (oxygen) sensors measure oxygen content in the exhaust. The PCM (powertrain control module) then uses this information to regulate fuel injector pulse. The o2 sensors are very important for the proper operation of the engine. Innacurate or faulty o2 sensors can cause the PCM to add or take away fuel based on the faulty o2 sensor voltage which can cause a host of problems.

Possible Causes:

• Bad O2 sensor
• Signal shorted to voltage
• Wiring problems due to contact with exhaust components
• Holes in exhaust near o2 sensor

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Decrease in MPG
• Increase in tailpipe emissions

O2 Sensor Circuit Malfunction Bank 2 Sensor 2

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit Low Voltage (Bank 2, Sensor 2)

Technical Description:

This code refers to a fault in the post-catalyst o2 sensor on Bank 2. First, a basic run-down of the catalyst: The Catalytic Converter is used to help control tailpipe emissions, to “clean up” the exhaust, if you will. The PCM (Powertrain Control Module) uses the signal from the heated oxygen sensor to the rear of the catalyst to monitor the catalyst’s efficiency by comparing it to the o2 sensors in front of the catalyst.

Possible Causes:

• Air leaks in exhaust in front of o2 sensor giving false reading
• Engine running excessively lean
• O2 sensor connector damaged/corroded
• O2 sensor signal circuit is shorted to ground
• O2 sensor ground circuit is open
• O2 sensor has failed (it may be contaminated with fuel or coolant)
• PCM has failed

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Engine performance issues
• Engine running rough
• Engine running rich (only if PCM is trying to add fuel to compensate for low o2 sensor voltage reading)
• Engine running lean (only if vacuum leak is large enough that PCM can’t compensate by adding fuel)
• Poor idle

O2 Sensor Circuit Low Voltage Bank 2 Sensor 2

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit High Voltage (Bank 2, Sensor 2)

Technical Description:

The catalytic converter is used to lower harmful emissions. To ensure proper operation, there is an O2 sensor located behind the catalyst that monitors the oxygen content of the exhaust after the cat. The PCM (Powertrain Control Module) then compares the post-cat reading to the pre-cat readings to determine if the catalyst is working properly.

Possible Causes:

• Bad o2 sensor (Bank 2 Sensor 2)
• Wiring in contact with exhaust components
• Engine running rich (If other codes are present)
• Holes in exhaust causing PCM to over-rich engine resulting in an abnormally high Bank 2, sensor 2 reading
• Short to voltage on signal circuit
• Bad PCM

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) on
• Engine loses power and misses intermittently
• May exhibit loss of fuel efficiency
• Engine running rich

O2 Sensor Circuit High Voltage Bank 2 Sensor 2

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks
– Exhaust gas leaks

Specific Makes:

– Possible higher than usual fuel consumption

Technical Definition:

O2 Circuit Slow Response (Bank 2, Sensor 2)

Technical Description:

Possible Causes:

• The oxygen sensor is faulty
• The wiring to the sensor is broken / frayed
• There is an exhaust leak

Possible Symptoms:

O2 Sensor Circuit Slow Response Bank 2 Sensor 2

Possible Solutions:

• Check and fix any exhaust leaks
• Check for wiring problems (shorted, frayed wires)
• Check the frequency and amplitude of the oxygen sensor (advanced)
• Check for a deteriorating / contaminated oxygen sensor, replace if necessary
• Check for inlet air leaks
• Check the MAF sensor for proper operation

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Rear Heated Oxygen Sensor Bank 2
– Rear Heated Oxygen Sensor Bank 2 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit High Voltage (Bank 2, Sensor 1)

Technical Description:

The o2 (oxygen) sensors basically measure oxygen content in the exhaust. The PCM (powertrain control module) then uses this information to regulate fuel injector pulse. The o2 sensors are very important to proper operation of the engine. Problems with them can cause the PCM to add or take away too much fuel based on the faulty o2 sensor voltage.

Possible Causes:

• Bad bank 2, 1 o2 sensor incorrectly reading rich condition
• Engine running rich and o2 sensor
• Correctly reading rich condition
• Signal shorted to voltage in harness
• Wiring harness damage/melted due to contact with exhaust components
• Vacuum leak (make have lean codes (P0171, P0174) present with it)
• Leaking injectors
• Bad fuel pressure regulator
• Bad PCM

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Engine may run very rough
• Engine may be running lean or rich depending on if the o2 sensor is reading correctly or incorrectly
• Lack of power
• Increased fuel consumption

O2 Sensor Circuit High Voltage Bank 2 Sensor 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Front Heated Oxygen Sensor Bank 2
– Intake air leaks may be faulty
– Exhaust gas leaks
– Front Heated Oxygen Sensor Bank 2 harness is open or shorted
– Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit Slow Response (Bank 2, Sensor 1)

Technical Description:

Possible Causes:

• The oxygen sensor is faulty
• The wiring to the sensor is broken / frayed
• There is an exhaust leak

Possible Symptoms:

O2 Sensor Circuit Slow Response Bank 2 Sensor 1

Possible Solutions:

• Check and fix any exhaust leaks
• Check for wiring problems (shorted, frayed wires)
• Check the frequency and amplitude of the oxygen sensor (advanced)
• Check for a deteriorating / contaminated oxygen sensor, replace if necessary
• Check for inlet air leaks
• Check the MAF sensor for proper operation
• Replace the Bank 2 oxygen sensor upstream of the catalytic converter

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Front Heated Oxygen Sensor Bank 2
– Front Heated Oxygen Sensor Bank 2 harness is open or shorted
– Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks
– Exhaust gas leaks

Specific Makes:

– Possible higher than usual fuel consumption

Technical Definition:

O2 Circuit No Activity Detected (Bank 2, Sensor 1)

Technical Description:

The oxygen sensors are critical to the engine running properly. It basically informs the PCM (Powertrain Control Module) of oxygen content of the exhaust. The PCM then uses this information to regulate fuel into the engine and maintain proper air:fuel ratio. It is a four wire sensor, with the PCM providing a reference/signal voltage of about half a volt (0.5v) to the sensor. It usually provides a ground also

Possible Causes:

• Faulty bank 2,1 Oxygen sensor
• Holes in exhaust near oxygen sensor
• Short to voltage or ground on signal circuit
• Open or high resistance in signal circuit
• Wiring harness chafing/rubbing on exhaust components
• Water/oil intrusion at O2 sensor connector
• Broken lock or loose terminals on O2 sensor connector
• Oil/coolant fouled oxygen sensor

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Other codes indicating rich or lean condition may be present
• Poor idle, won’t idle
• Misfire at idle or at highway speed
• Engine may blow black smoke at tailpipe
• Fuel economy may decrease
• May start and stall

O2 Sensor Circuit No Activity Detected Bank 2 Sensor 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Front Heated Oxygen Sensor Bank 2
– Front Heated Oxygen Sensor Bank 2 harness is open or shorted
– Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Heater Circuit (Bank 2, Sensor 1)

Technical Description:

The code refers to the front oxygen sensor on Bank 2. 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.

Possible Causes:

• 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 Symptoms:

O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1

Possible Solutions:

• Repair short or open or high resistance in wiring harness or harness connectors
• Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit fuse
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted to ground
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection
– Faulty Engine Control Module (ECM)

Specific Makes:

– Possible higher fuel consumption
– Possible more smoke from exhaust than usual

Technical Definition:

O2 Circuit Low Voltage (Bank 2, Sensor 1)

Technical Description:

Possible Causes:

• Faulty o2 oxygen sensor
• Short to voltage on O2 signal circuit
• High resistance or open on O2 signal circuit

Possible Symptoms:

O2 Sensor Circuit Low Voltage Bank 2 Sensor 1

Possible Solutions:

• Replace faulty sensor
• Repair short, open, or high resistance on o2 signal circuit

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Front Heated Oxygen Sensor Bank 2
– Front Heated Oxygen Sensor Bank 2 harness is open or shorted
– Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive smoke from Exhaust

Technical Definition:

O2 Circuit (Bank 2, Sensor 1)

Technical Description:

The O2 sensor produces a voltage based on oxygen content in the exhaust. The voltage varies between .1 and .9 Volts, .1 indicating lean and .9 indicating rich.

Possible Causes:

• Water or corrosion in the connector
• Loose terminals in the connector
• Wiring burnt on exhaust components
• Open or short in the wiring due to rubbing on engine components
• Holes in exhaust allowing unmetered oxygen into exhaust system
• Unmetered vacuum leak at the engine
• Bad o2 sensor
• Bad PCM

Possible Symptoms:

O2 Sensor Circuit Malfunction Bank 2 Sensor 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Front Heated Oxygen Sensor Bank 2
– Front Heated Oxygen Sensor Bank 2 harness is open or shorted
– Front Heated Oxygen Sensor Bank 2 circuit poor electrical connection
– Inappropriate fuel pressure
– Faulty fuel injectors
– Intake air leaks may be faulty
– Exhaust gas leaks

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Heater Circuit (Bank 1, Sensor 3)

Technical Description:

O2 (Oxygen) sensors contain a heating element that allows the sensor to reach operating temperature quickly. This lowers emissions since it allows the engine to reach closed loop faster and also allows the engine to stay in closed loop at idle.

Possible Causes:

• Bad o2 sensor heater circuit
• Bad o2 sensor
• Wiring harness problems

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) illumination
• Poor/ rough idle

O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 1 Sensor 3
– Heated Oxygen Sensor Bank 1 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 1 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

Fuel Delivery Error

Technical Description:

Possible Causes:

Possible Symptoms:

Fuel Delivery Error

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Severely restricted fuel filter.
– Severely restricted fuel supply line.

Specific Makes: