Engine-Codes - Generic - P1166

P1166 Code - Air/Fuel Ratio Sensor 1 Heater Circuit Malfunction

- Code Popularity: 11,551 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 2/3
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What are the Possible Causes of the DTC P1166?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty Air/Fuel Ratio Sensor 1
  • Air/Fuel Ratio Sensor 1 harness is open or shorted
  • Air/Fuel Ratio Sensor 1 circuit poor electrical connection
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How to Fix the DTC P1166?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P1166 code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

When is the Code Detected?

If the element is not activated or the Engine Control Module (ECM) terminal voltage is a set value or less for at least a set time period when the power is drawn to the A/F sensor (sensor 1) heater, a malfunction is detected and the code is stored.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P1166 Code Mean?

The Air/Fuel Ratio (A/F) sensor 1 is installed in the exhaust system and detects oxygen content in the exhaust gas. The A/F sensor transmits output voltage to the Engine Control Module (ECM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It is activated and heats the sensor to stabilize and speed the detection of oxygen content by controlling current flowing through the heater. An increase in the current levels off as the applied voltage to the element electrode reaches a certain range because the amount of oxygen which is led through the diffusion layer is limited. The current amperage is proportional to oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measurement of the current amperage. The ECM compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection timing.
If the A/F sensor (sensor 1) voltage is low, the air/fuel ratio is lean, and the ECM uses A/F feedback control to issue a Rich command. If the A/F sensor (sensor 1) voltage is high, the air/fuel ratio is rich, and the ECM uses A/F feedback control to issue a Lean command.

P1166 Code - Air/Fuel Ratio Sensor 1 Heater Circuit Malfunction

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Code P1166 Information for Specific Makes

  • P1166 Acura Air/Fuel Ratio Sensor 1 Heater Circuit Malfunction
  • P1166 Audi Bank 1 Long Term Fuel Trim Range 2 Rich Upper Limits Exceeded
  • P1166 Honda Air/Fuel Ratio Sensor 1 Heater Circuit Malfunction  
  • P1166 Hyundai O2 Sensor System Lambda Controller at the Limit Bank 1
  • P1166 Infiniti Heated Oxygen Sensor 2 Minimum Voltage Monitoring Bank 2
  • P1166 KIA O2 Sensor System Lambda Controller at the Limit Bank 1
  • P1166 Nissan Heated Oxygen Sensor 2 Minimum Voltage Monitoring Bank 2
  • P1166 Suzuki HO2S Circuit Low Voltage During Power Enrichment Sensor 1
  • P1166 Volkswagen Bank 1 Long Term Fuel Trim Range 2 Rich Upper Limits Exceeded

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