Heated Oxygen Sensor Insufficient Switching Bank 2 Sensor 2 (Ford)
What does P1138 mean?
The P1138 code means the vehicle's onboard diagnostic system has detected: Heated Oxygen Sensor Insufficient Switching Bank 2 Sensor 2 (Ford). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Poor fuel economy
- Failed emissions inspection
- Slight exhaust odor
- Minimal drivability symptoms
Probable Causes (Ranked by Likelihood)
- Failing downstream oxygen sensor (Bank 2 Sensor 2) Very High
- Exhaust leak near the downstream sensor High
- Catalytic converter degradation on Bank 2 Moderate
- Damaged O2 sensor wiring harness Moderate
- Rich running condition affecting Bank 2 Low
Step-by-Step Diagnostic Procedure
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Use a scan tool to monitor Bank 2 Sensor 2 voltage and switching rate
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Check for exhaust leaks around the Bank 2 catalytic converter and piping
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Compare Bank 2 upstream and downstream O2 sensor waveforms
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Inspect the sensor connector and wiring for corrosion or heat damage
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Replace the Bank 2 downstream O2 sensor if it shows sluggish response
Frequently Asked Questions
What is Bank 2 on a Ford V8?
On Ford V8 engines, Bank 2 is the side of the engine that does not contain cylinder 1. On most Ford V8s, Bank 1 is the passenger side and Bank 2 is the driver side, though this varies by model.
Can P1137 and P1138 appear together?
Yes. If both downstream O2 sensors are failing simultaneously, both codes can set. This is common on high-mileage vehicles where both sensors have similar wear. Replacing both sensors at the same time is recommended.
How long do O2 sensors last?
Heated oxygen sensors typically last 60,000 to 100,000 miles. Factors like fuel quality, oil consumption, and coolant leaks can shorten their lifespan. Downstream sensors often last longer than upstream sensors.