Engine Performance (A8)第 99 / 120 题
A P0420 code (catalyst efficiency below threshold) most often indicates:
a.A degraded catalytic converter or an O2 sensor issue
b.A slipping transmission
c.A worn wheel bearing
d.A faulty ABS sensor
解析
P0420 sets when the downstream O2 sensor signal mirrors the upstream too closely, suggesting the converter is no longer storing oxygen effectively. Causes include a worn converter, exhaust leaks, or faulty sensors. Underlying misfires or rich running can damage the converter and must be addressed first.
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