Catalyst Temperature Sensor Circuit Bank 2 Low (Generic)
The P4021 code means the vehicle's onboard diagnostic system has detected: Catalyst Temperature Sensor Circuit Bank 2 Low (Generic). This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $120 - $450 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Low bank 2 catalyst temperature reading
- Bank 2 catalyst efficiency not verified
- Possible false catalyst codes
Probable Causes (Ranked by Likelihood)
- Short to ground in bank 2 sensor wiring Very High
- Failing bank 2 sensor High
- Corroded connector at bank 2 Moderate
- Ground circuit fault Low
Step-by-Step Diagnostic Procedure
-
Test sensor resistance and compare to specification
-
Check for shorts to ground in bank 2 wiring
-
Inspect connector for corrosion
-
Compare bank 1 and bank 2 readings
Frequently Asked Questions
Can P4021 cause a false P0430?
Yes, inaccurate catalyst temperature data can cause the PCM to incorrectly evaluate catalyst efficiency on bank 2, potentially setting a false P0430.
Can I drive with P4021?
You can drive short distances. The catalyst is likely working but the monitoring cannot verify it.
How do I know if it is the sensor or wiring?
Measure sensor resistance at the connector. If resistance is normal, the fault is in the wiring. If resistance is out of spec, the sensor has failed.
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