P0138 Oxygen Sensor Circuit High Voltage
P0138 is a generic OBD-II powertrain code...
It indicates that Bank 1 Sensor 2 oxygen sensor voltage is higher than expected.
Symptoms:
• Check Engine Light
• Poor fuel economy
• Rich fuel mixture
Common Causes:
• Faulty O2 sensor
• Wiring damage
• Fuel mixture problems
• Exhaust leaks
Diagnosis:
1. Scan live O2 sensor data
2. Inspect wiring
3. Check fuel trims
4. Test sensor response
Repair Cost:
$100–$400 depending on vehicle.
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