Applicable Systems
OBD-II
Symptoms
The downstream oxygen sensor for bank 1 is not switching as expected. Catalyst may be degraded.
Possible Causes
- Catalyst efficiency below threshold
- O2 sensor contaminated or slow
- Exhaust leak between catalyst and sensor
- Sensor calibration drift
- ECM catalyst monitor fault
Troubleshooting Steps
- Step 1: Connect an OBD-II scan tool and read all stored DTCs and freeze frame data
All DTCs and freeze frame data are retrieved - Step 2: Inspect the related sensor or actuator wiring for damage, corrosion, or loose connections
Wiring and connectors are in good condition - Step 3: Use a digital multimeter to check sensor voltage, resistance, and reference signals per manufacturer specifications
Values are within specified range - Step 4: Perform component-level testing of the suspected sensor or actuator
Component passes or fails definitively - Step 5: Clear codes and road test to verify repair
Code does not return and system operates normally
How to Reset
To reset code P1420: 1) Repair the underlying fault. 2) Use an OBD-II scan tool to clear the DTC. 3) Perform a drive cycle.
Frequently Asked Questions
- Q: What does OBD-II code P1420 mean?
Code P1420 indicates: Oxygen Sensor Bank 1 Sensor 2 Range/Performance. This is a Toyota manufacturer-specific diagnostic trouble code.
- Q: Is code P1420 serious?
Severity: Major. Service as needed.
- Q: How do I fix code P1420?
Diagnose the O2 Sensor system and replace faulty components.
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Source: OBD-II Manufacturer Extended Codes / SAE J2012 / OBD-Codes.com
Category: OBD-II
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