Chrysler PT Cruiser 2001 Service Manual Supplement page 2581

Symptom:
P0420-1/1 CATALYTIC CONVERTER EFFICIENCY
When Monitored and Set Condition:
P0420-1/1 CATALYTIC CONVERTER EFFICIENCY
When Monitored: After engine warm up to 76°C (170°F), 180 seconds of open throttle
operation, at a speed greater than 32 KMH (20 MHP), with the engine at 1200-1600 rpm
and MAP vacuum between 15.0 and 18.0 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.
CATALYST EFFICIENCY DTC DOES NOT REOCCUR
ENGINE MECHANICAL PROBLEM
EXHAUST LEAK
CATALYTIC CONVERTER
UPSTREAM O2 SENSOR OLDER THAN DOWNSTREAM O2 SENSOR
TEST
1 Turn the ignition on.
With the DRB, read the DTCs.
Is the Good Trip counter displayed and equal to zero?
Yes → Go To 3
No
2 At this time the Catalyst Efficiency Failure does not exist or is an intermittent
problem.
With the DRB, read the FREEZE FRAME data.
With this screen, attempt to duplicate the condition that has set this fault.
While using FREEZE FRAME pay particular attention to the fault setting condi-
tions, such as speed, temp, load, and map vacuum.
Does the Catalyst Efficiency Failure Reoccur?
Yes → Go To 3
No
3 Check the exhaust for excessive smoke from internal oil or coolant leaks.
Is there an oil or coolant consumption condition present?
Yes → Repair engine mechanical condition as necessary and replace
No
POSSIBLE CAUSES
ACTION
→ Go To 2
→ The Catalytic Conveter Efficiency Failure no longer exists.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
Catalytic Converter.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
→ Go To 4
DRIVEABILITY - GAS
121
APPLICABILITY
All
All
All