Having problems with your 2000 Mitsubishi Montero Sport ?
Trying to find out what this code is PO421 - 2000 Mitsubishi Montero Sport
Warm-up catalyst efficiency below threshold [bank 1] means the o2 sensor after the cat converter is detecting that ur cat is not working up to specs [correctly] can be a fouled plug-faulty o2 sensor- or cat converter is starting to go bad
Repair Help & Product Troubleshooting for 2000 Mitsubishi Montero Sport
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