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P Codes (powertrain)
P0400 - P0499
Diagnostic shows P0420, how do I repair that.
1997 MERCURY MARQUIS
Catalyst system Efficiency Below Threshold Bank 1 is what shows up. Took it in auto zone did a diagnostic and showed cadalack coverter. But today showed the P0420
have the same problem?
Friday, June 8th, 2012 AT 4:36 PM
Best to have a pro look at it. It can be a converter bad, a coolant leak cooling off the converter, a bad O2 sensor, many things.
Please consider a
to help us answer more questions.
Friday, June 8th, 2012 AT 4:48 PM
to post a reply.
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