P1131 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
- Faulty Upstream Oxygen Sensor Bank 1
- Fuel pressure high or low
- MAF sensor dirty/defective
- Vacuum leak on engine
- Leaking fuel injector or fuel pressure regulator
- Faulty Powertrain Control Module (PCM)
- Engine Light ON (or Service Engine Soon Warning Light)
• The HO2S sensor senses the oxygen content in the exhaust flow and outputs a voltage between zero and 1.0 volt. Lean of stoichiometric (air/fuel ratio of approximately 14.7:1 for gasoline engines), the HO2S will generate a voltage between zero and 0.45 volt. Rich of stoichiometric, the HO2S will generate a voltage between 0.45 and 1.0 volt.
• The HO2S Monitor evaluates both the upstream (Fuel Control) and downstream (Catalyst Monitor) HO2S for proper function.
• Once the HO2S Monitor is enabled, the upstream HO2S signal voltage amplitude and response frequency are checked. Excessive voltage is determined by comparing the HO2S signal voltage to a maximum calibratable threshold voltage.
• A fixed frequency closed loop fuel control routine is executed and the upstream HO2S voltage amplitude and output response frequency are observed. A sample of the upstream HO2S signal is evaluated to determine if the sensor is capable of switching or has a slow response rate.
• An HO2S heater circuit fault is determined by turning the heater on and off and looking for a corresponding change in the OSM and by
measuring the current going through the heater circuit.
• The MIL is activated after a fault is detected on two consecutive OBD II drive cycles.
P1131 Information for specific makes
P1131 BMW Oxygen Sensor Behind Catalytic Converter 2 Ageing
P1131 BUICK HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 CADILLAC HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 CHEVROLET HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 CHRYSLER Glow Plug Control Module Internal Fault-Voltage Supply Concern
P1131 FORD Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 GMC HO2S Circuit Low Variance Bank 1 Sensor 2
P1131 HYUNDAI Injection Quantity Adjust
P1131 INFINITI Swirl Control Valve Control Solenoid Valve
P1131 LINCOLN Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 MAZDA Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1
P1131 MERCURY Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
P1131 MINI Oxygen Sensor Behind Catalytic Converter 2 Ageing
P1131 NISSAN Swirl Control Valve Control Solenoid Valve
P1131 SUBARU Front Oxygen Sensor Circuit Malfunction Short Circuit
P1131 SUZUKI HO2S11 Circuit Low Voltage Shift/High Voltage
P1131 VOLKSWAGEN HO2S21 Inner Resistance Too Large
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