DanK
Dodge Dakota
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11/18/2005
23:09:42
|  RE: trouble code p0420?
IP: Logged
Message:
Catalyst 1/1 is the left, or driver side catalytic converter. Depending on what year and emissions system, you could have only one catalytic converter monitored by O2 sensors, in which case it’s that one.
From the FSM
P0420-CATALYST 1/1 EFFICIENCY
When Monitored: After engine warm up to 70°C (158°F), 180 seconds of open throttle
operation, at a speed greater than 18 mph and less than 55 mph, with the engine at
1200-1700 rpm and MAP vacuum between 15.0 and 21.0 inches of mercury (Hg).
Set Condition: As catalyst efficiency deteriorates, the switch rate of the downstream O2 sensor approaches that of the upstream O2 sensor. If at any point during the test the switch ratio reaches a predetermined value a counter is incremented by one.
This means the downstream O2 sensor is telling the computer that the catalytic converter isn’t working as efficiently as it should. The problem could be the cat, or the downstream O2 sensor
Here’s what the FSM gives as possible causes:
EXHAUST LEAK
ENGINE MECHANICAL CONDITION
AGING O2 SENSOR
CATALYTIC CONVERTER
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