Can this b a o2 sensor or a cats bad
Nov 12, 2014 at 6:46 PM
2007 Cadillac CTS code 420
2007 CADILLAC CTS
CODY805KALI
- MEMBER
- 1 POST
Advertisement
CARADIODOC
- ✓ASE Certified Mechanic
- 34,321 POSTS
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The rear oxygen sensor is switching between "lean" and "rich" too fast which indicates no change is taking place in the makeup of the exhaust gas. What's going in and being detected by the front sensor is the same as what's going out and being detected by the rear sensor. To determine that, both sensors have to be working. When they detect the same thing, it's because the catalytic converter isn't doing its job. That sets code 420.
The rear oxygen sensor is switching between "lean" and "rich" too fast which indicates no change is taking place in the makeup of the exhaust gas. What's going in and being detected by the front sensor is the same as what's going out and being detected by the rear sensor. To determine that, both sensors have to be working. When they detect the same thing, it's because the catalytic converter isn't doing its job. That sets code 420.
Nov 12, 2014 at 11:50 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.