I took my astro to get inspected and it failed because the engine light says on on 1998 Chevrolet Astro

But the light is not on. How do I replace the bulb?
A friend took off the battery and replaced an oxygen sensor and I thought the issue was resolved, but when I took it back to get it inspected after driving 300 miles, now they say the engine light is on but it is not. It also is giving a P0420 code. Any suggestions would be appreciated. Thanks rkl

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2 answers
420 code is an efficiency code for cat converter. it is not doing its job anymore. it most likely needs to be replaced and a drive cycle performed. then you need to get the light to work.

Roy
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