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2001 Chevy Malibu ENGINE LIGHT

Tiny
1262DOG
  • MEMBER
  • 2001 CHEVROLET MALIBU
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 103,000 MILES
FOR OVER A YEAR HAVE BEEN FIGHTING WITH ENGINE LIGHT COMING ON AFTER EVERY REPAIR THAT CODES SAY, REPLACE EGR VALVE, O2 SENSORS TWICE, CONVERTER. LIGHT STILL KEEPS COMING AFTER A COUPLE OF MONTHS AFTER REPAIR. LIGHT CAME ON AGAIN WITH CODE SAYING
CAT BAD READING, ANY ANSWERS FOR IT. PLEASE
ANY IDEAS.
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Tuesday, March 2nd, 2010 AT 3:52 PM

3 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
If you can post the actual codes, it could help, GM had a PCM reflash to correct certain EGR code.
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Tuesday, March 2nd, 2010 AT 3:58 PM
Tiny
1262DOG
  • MEMBER
  • 2 POSTS
THE CODE WAS PO420
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Wednesday, March 3rd, 2010 AT 1:52 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
OK P0420 is not and EGR code, it's for catalyst efficiency! And either the cat is bad, or the O2 sensor after the cat is switching too much, a scantool that reads live sensor data will show a bad downstream O2 as a graph with a lot of high and low peaks, a good one has an almost flat line after the cat and high peaks on the sensor before the cat.


https://www.2carpros.com/forum/automotive_pictures/62217_P0430a_3.jpg



https://www.2carpros.com/forum/automotive_pictures/62217_P0430b_High_3.jpg


Top picture shows a bad sensor, bottom picture shows a good sensor. Or bad cat!
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Friday, March 5th, 2010 AT 3:25 PM

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