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Service engine light

Tiny
MARK ANTHONY STEWART
  • MEMBER
  • 2000 BUICK LESABRE
  • 145,000 MILES
Recently my service engine light came on and started blinking. The car started idling and has been doing this every since I took it to auto zone and put it on the diagnostics. Machine and these codes came back p0300, p0440 and p0420. Any idea what these codes mean? My mechanic thinks it is the coils. What is your opinion?
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Sunday, February 19th, 2017 AT 8:59 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,752 POSTS
P0300 - Random/Multiple Cylinder Misfire Detected.
P0420 - Catalyst System Efficiency Below Threshold (Bank 1).
P0440 - Evaporative Emission Control System Malfunction.

The type of ignition system and specific parts depends on which engine you have. You did not list that.

The flashing Check Engine light indicates the most serious of conditions, and you are supposed to stop the engine right away. Too much unburned fuel is going into the exhaust system where it will burn in the catalytic converter and damage it. Code 420 indicates this may have happened already. The first thing to address is the code 300. That could indeed be caused by a weak ignition coil, but based on the mileage, an equally-good suspect is worn spark plugs and wires. You might want to start with a general tune-up, erase the fault codes, then see which ones set again. Code 300 with the flashing Check Engine light suggests the misfires are spark-related, not fuel-related.
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Sunday, February 19th, 2017 AT 6:48 PM

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