Ford Ranger OBD code

Old 03-11-05, 04:32 PM
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Question Ford Ranger OBD code

I have a P0420 check engine code showing on my 1996 Ford Ranger, 2.3L 4 cylinder. Any ideas on diagnosis?

Old 03-11-05, 05:21 PM
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Generic codes:
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

I don't know much about those O2 sensers mounted behind the cat.

Lets see, hmmm, Bank 1. This is to throw us off, because there is only 1 bank, not 2.

Im stumped. If bank 1 were running rich or lean, I would expect to see that code before the cat. Is that the only code you have? Were there others?
Maybe the cat has used up its 9 lives and needs to be replaced?
Old 03-11-05, 05:49 PM
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usually it is the catylitic convertor causing a code 420 if no other codes are stored, might check with the dealer to see if any tsb or updates have been issued for that specific problem. [check engine light code p0420]
the computer monitors the readings of the upstream and downstream o2 sensors and as the cat gets bad the readings from the rear o2 will be out of spec and set off the engine light.
Old 03-11-05, 08:58 PM
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A Ford Dealer can quickly hook up the scan tool & monitor the signal fron the CAT monitor. If the Tech compares it to the signal from the O2 sensor & they almost follow the same pattern, The CAT needs replaced as it's not working. If the signal from the CAT monitor is a steady voltage, it'll need more diagnosis to pinpoint the fault. Good Luck (R)

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