Code P0300, service engine light, several issues with emission system?

Tiny
RWALBROEHL
  • MEMBER
  • 2003 CHEVROLET S-10
  • 2.2L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 71,000 MILES
Had several issues with the emission system. Previous was code P0440 and P0442 Change purge solenoid coil valve. The light cleared and ran fine. After, still getting light and checked gas a was running rough. Change gas filter and put on Lucas complete engine conditioner. Reset light ran fine last couple of 5 mile runs. Yesterday service engine light again with code P0300 Catalyst System low efficiency. Catalyst system efficiency below threshold bank 1. Truck runs fine but I'm worried if I would cause any damage driving it.
Tuesday, January 21st, 2025 AT 2:52 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,264 POSTS
Code P0300 is for a random engine misfire? Is the engine idling rough? This will cause this code.

Here is a guide to help us go over the problem that can cause this issue:

https://www.2carpros.com/articles/repairing-engine-rough-idle-issues

Please go over this guide and get back to us.
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Wednesday, January 22nd, 2025 AT 9:07 AM
Tiny
RWALBROEHL
  • MEMBER
  • 107 POSTS
Sorry Kevin,
Code was PO420. My phone auto corrected to wrong code #. Looking on code reader said catalytic converter low efficiency bank 1. Is it possible that oxygen sensor in the front or back of the converter can cause this problem before I change the expensive converter out. Thank you for your help, Bob
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Wednesday, January 22nd, 2025 AT 1:17 PM
Tiny
RWALBROEHL
  • MEMBER
  • 107 POSTS
I had previous admission problems which told me to change out the purge solenoid coil which I did and also I changed out by your recommendation the fuel filter to a brand new one check the fuel for water and then also put in Lucas's complete engine conditioner and now I've got this other code about the catalytic converter low efficiency bank 1.
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Wednesday, January 22nd, 2025 AT 1:19 PM
Tiny
RWALBROEHL
  • MEMBER
  • 107 POSTS
These are scanner picture and video.
Image & Video (Click to make bigger)
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Thursday, January 23rd, 2025 AT 8:42 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,264 POSTS
No problem please start a new thread so I can help and reload these posts, sorry, we only handle one problem per thread, please post your new question here, you must be logged in.

https://www.2carpros.com/questions/new

Cheers, Ken
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Thursday, January 23rd, 2025 AT 11:16 AM

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