Technical Definition:

System Too Lean (Bank 1)

Technical Description:

Possible Causes:

Possible Symptoms:

System Too Lean Bank 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Intake air leaks
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Lack of fuel
– Faulty Mass Air Flow (MAF) sensor
– Incorrect Positive Crankcase Ventilation (PCV) hose connection

Specific Makes:

– Excessive Fuel Consumption

Technical Definition:

System Too Rich (Bank 1)

Technical Description:

Possible Causes:

Possible Symptoms:

System Too Rich Bank 1

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Faulty Mass Air Flow (MAF) sensor

Specific Makes:

– Excessive Fuel Consumption

Technical Definition:

Fuel Trim (Bank 2)

Technical Description:

Possible Causes:

Possible Symptoms:

Fuel Trim Malfunction Bank 2

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Intake air leaks
– Faulty front heated oxygen sensor
– Ignition misfiring
– Faulty fuel injectors
– Exhaust gas leaks
– Incorrect fuel pressure
– Lack of fuel
– Faulty Mass Air Flow (MAF) sensor
– Incorrect Positive Crankcase Ventilation (PCV) hose connection

Specific Makes:

– Excessive Fuel Consumption

Technical Definition:

O2 Circuit No Activity Detected (Bank 2, Sensor 3)

Technical Description:

Possible Causes:

• Bad Bank 2, position 3, o2 sensor
• Wiring problem, melted harness, broken connectors, etc.
• Bad PCM

Possible Symptoms:

• Malfunction Indicator Lamp on
• May idle or drive poorly
• Fuel economy may decrease

O2 Sensor Circuit No Activity Detected Bank 2 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Heater Circuit (Bank 2, Sensor 3)

Technical Description:

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 2 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

Fuel Temperature Too High

Technical Description:

Possible Causes:

Possible Symptoms:

Fuel Temperature Too High

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

Specific Makes:

Technical Definition:

Incorrect Fuel ComPosition

Technical Description:

Possible Causes:

Possible Symptoms:

Incorrect Fuel Composition

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty fuel condition detected
– Faulty Fuel Composition Sensor

Specific Makes:

Technical Definition:

O2 Circuit High Voltage (Bank 2, Sensor 3)

Technical Description:

Possible Causes:

• Bad O2 sensor (Bank 2 Sensor 3)
• Wiring in contact with exhaust components
• Engine running rich (If other codes are present)
• Holes in exhaust near Bank 2 Sensor 3
• 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

O2 Sensor Circuit High Voltage Bank 2 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit Slow Response (Bank 2, Sensor 3)

Technical Description:

Possible Causes:

Possible Symptoms:

O2 Sensor Circuit Slow Response Bank 2 Sensor 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

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

Technical Description:

This code is for a post-catalyst oxygen sensor that isn’t operating porperly or not at all. The catalyst, or catalytic converter is used to control emissions. This particular o2 sensor on Bank 2, position 2 is after the converter on bank 2 and monitors the catalyst efficiency of the catalytic converter on that bank.

Possible Causes:

• Holes in exhaust near post cat o2 sensor
• Bad Bank 2, position 2, o2 sensor
• Wiring problem, melted harness, broken connectors, etc.
• Bad PCM

Possible Symptoms:

• MIL (Malfunction Indicator Lamp) on
• May idle or drive poorly
• Fuel economy may decrease

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

Technical Description:

It basically means the PCM detected either an excessive current draw, or an open or short in the circuit powering the oxygen sensor’s heater circuit. This is in reference to the Heated Oxygen Sensor (2) located rear of catalytic converter (Bank 2).

Possible Causes:

• HO2S heater power circuit open
• HO2S heater ground circuit open
• HO2S signal tracking (due to oil or moisture in the connector)
• HO2S is damaged or has failed PCM has failed

Possible Symptoms:

HO2S Heater Performance Bank 2 Sensor 2

Possible Solutions:

• Replace HO2 Sensor
• Repair open or short in power circuit
• Repair open or short in ground circuit
• Repair damaged connector due to tracking

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 (Bank 2, Sensor 3)

Technical Description:

The O2 (oxygen) sensors measure oxygen content in the exhaust, whether rich or lean. The PCM (powertrain control module) then uses this information to regulate fuel injector pulse in order to keep the proper air:fuel ratio. The O2 sensors are very important for the proper operation of the engine.

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 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust

Technical Definition:

O2 Circuit Low Voltage (Bank 2, Sensor 3)

Technical Description:

The code refers to a fault in one of the post-catalyst O2 sensors on Bank 2. This oxygen sensor is used for a specific purpose. This is it in a nutshell: The Catalytic Converter is used to help control emissions, to “clean up” the exhaust gasses. The PCM (Powertrain Control Module) uses the signal from post catalyst heated oxygen sensors to monitor the catalyst’s efficiency by comparing it to the O2 sensors in front of the catalyst. If the PCM sees little or no difference between the exhaust quality in post- and pre- catalyst sensors then it knows that the catalyst is not working properly.

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 3

Possible Solutions:

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Faulty Heated Oxygen Sensor Bank 2 Sensor 3
– Heated Oxygen Sensor Bank 2 Sensor 3 harness is open or shorted
– Heated Oxygen Sensor Bank 2 Sensor 3 circuit poor electrical connection

Specific Makes:

– High Fuel Consumption
– Excessive Smoke from Exhaust