Applicable Systems
OBD-II
Symptoms
Oxygen sensor signal out of range; ECM cannot maintain closed-loop fuel control; emissions may exceed limits.
Possible Causes
- O2 sensor heater element failure
- O2 sensor signal wire open/short
- Sensor contaminated by coolant or silicone
Troubleshooting Steps
- Step 1: Check O2 sensor heater resistance (6-20 ohm)
Resistance within range - Step 2: Check sensor signal wire for open/short
Wiring intact - Step 3: Inspect sensor for contamination (white=coolant, black=rich)
Sensor clean - Step 4: Replace O2 sensor if faulty
New sensor signal switches normally - Step 5: Clear code and verify closed-loop operation
O2 sensor switches rich/lean
How to Reset
Clear with OBD-II scanner; verify fuel trim returns to normal.
Common Replacement Parts
- O2 Sensor Bank 1 Sensor 1 (OEM spec)
Frequently Asked Questions
- Q: What is Bank 1 Sensor 1?
Bank 1 = cylinder bank with cylinder #1. Sensor 1 = upstream (before catalytic converter). This is the primary fuel control sensor.
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Source: SAE J2012 standard DTC list + OBD-II portal
Category: OBD-II
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