Chrysler PT Cruiser 2001 Service Manual Supplement page 2582

DRIVEABILITY - GAS
P0420-1/1 CATALYTIC CONVERTER EFFICIENCY —
TEST
4 Start Engine and let idle.
Check for exhaust leaks between the engine and the appropriate downstream O2
Sensor.
Is there any exhaust leaks?
Yes → Repair or replace leaking exhaust parts as necessary.
No
5 Note: A new Downstream O2 Sensor along with an aging Upstream O2
Sensor may cause this trouble code to set.
Review vehicle repair history.
Has the Downstream O2 Sensor been replaced without replacing the Upstream O2
Sensor?
Yes → Replace the appropriate Upstream Oxygen Sensor.
No
6 If there are no possible causes remaining, view repair.
Repair
ACTION
→ Go To 5
Perform POWERTRAIN VERIFICATION TEST VER - 5.
→ Go To 6
Replace the Catalytic Converter.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
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Continued
APPLICABILITY
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