Having problems with your 2002 Mitsubishi Lancer ?

REplaced the cat and 02 sensors. Did the recalls. Also did a tune up, excluding the fuel filter. PO421 code is on again. Checked for exhaust leaks and vacuum leaks. Flushed the injectors. Next is checking the MAF sensor for dirt and replacing ignition coils. What else could we be missing?

Posted / edited by AnonymousUser on : 24-01-2022

Answers :

P0421....Warm Up Catalyst Efficiency Below Threshold (Bank 1)
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check the heater circuits on the O2 sensors ,the two wires the same colour are the heater wires check across these two for 12v with ignition on and engine running

Repair Help & Product Troubleshooting for 2002 Mitsubishi Lancer

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