Engine-Codes - Cadillac - P0151 Cadillac

P0151 Cadillac Code - HO2S Circuit Low Voltage Bank 2 Sensor 1

- Code Popularity: 13,975 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 2/3
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What are the Possible Causes of the DTC P0151 Cadillac?

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 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
  • Low or high fuel system pressure
  • Fuel contamination
  • Faulty fuel injectors
  • Exhaust gas leaks
  • Engine vacuum leaks

Code Tech Notes

Replacing the Front Heated Oxygen Sensor (HO2S) Bank 2 usually takes care of the problem.

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How to Fix the DTC P0151 Cadillac?

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 P0151 Cadillac 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.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • High Fuel Consumption
  • Excessive smoke from Exhaust

What Does the P0151 Cadillac Code Mean?

The Heated Oxygen Sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the Engine Control Module (ECM) operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0 - 1, 000 mV. Once sufficient HO2S voltage fluctuation is observed by the ECM, Closed Loop is entered. The ECM uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases toward 1, 000 mV indicates a rich fuel mixture. An HO2S voltage that decreases toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the ECM to calculate the air-to-fuel ratio sooner.
The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the heated oxygen sensor is shorted to ground if the HO2S voltage is less than 50 mV.
P0151 Cadillac Code - HO2S Circuit Low Voltage Bank 2 Sensor 1

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