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P1151 1997 FORD F150

P1151 1997 FORD F150 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2

Repair Importance Level: 3/3
Repair Difficulty Level: 2/3  What does this mean?

P1151 1997 FORD F150 Possible Causes

  • Faulty Upstream Oxygen Sensor Bank 2
  • 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)

First diagnose P1151 1997 FORD F150 code

    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 terminals.

P1151 1997 FORD F150 Tech Notes

The code means that the Powertrain Control Module (PCM) has detected a lean system, which means that there is either not enough fuel or and excessive amount of air in the system. Start by checking for vacuum leaks.

Cost of diagnosing the P1151 1997 FORD F150 code

    Labor: 1.0

    The cost of diagnosing the P1151 1997 FORD F150 code is 1.0 hour of labor. The auto repair labor rates vary widely across the country, and even within the same city. Most auto repairs shops charge between $75 and $150 per hour.

When is the P1151 1997 FORD F150 code detected?

When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.

P1151 1997 FORD F150 Possible Symptoms

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

P1151 1997 FORD F150 Meaning

The Heated Oxygen Sensor (HO2S) Monitor is an on-board strategy designed to monitor the HO2S sensors for a malfunction or deterioration that can affect emissions. Under specific conditions, the fuel control or upstream HO2S sensors are checked for proper output voltage and response rate (the time it takes to switch from lean to rich or rich to lean). Downstream HO2S sensors used for Catalyst Monitor are also monitored for proper output voltage. Input is required from the Engine Coolant Temperature (ECT) or Cylinder Head Temperature (CHT), Inlet Air Temperature (IAT), Mass Air Flow (MAF), Throttle Position (TP) and Crankshaft Position (CKP) sensors to activate the HO2S Monitor. The Fuel System Monitor and Misfire Detection Monitor must also have completed successfully before the HO2S Monitor is enabled.

• 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.

OBDII Code P1151 1997 FORD F150 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2 - Engine-Codes.com

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