P0420 Catalyst System Efficiency below Threshold (Bank 1)

/ Engine DTCs / By
COMPONENT LOCATION

img

GENERAL DESCRIPTION
The ECM uses dual oxygen sensors to monitor the efficiency of the manifold catalytic converter (warm-up catalytic converter). By monitoring the oxygen storage capacity of a catalyst, its efficiency can be indirectly calculated. The upstream HO2S is used to detect the amount of oxygen in the exhaust gas before it enters the catalytic converter. A low voltage indicates high oxygen contents (lean air mixture). A high voltage indicates low oxygen contents (rich air mixture). When the catalyst is working properly, it used oxygen in the exhaust. The oxygen levels coming out of the catalyst should be lower and a more stable level. This would produce a somewhat level HO2S reading around 700 to 800 mv. When the catalyst efficiency drops, no chemical reaction takes place. This means the concentration of oxygen will be the same at the rear as it is at the front of the catalyst. This will give a HO2S reading simular to the upstream sensor.
DTC DESCRIPTION
If the oxygen storage time for Bank 1 is lower than threshold, the ECM determines that a fault exists and a DTC is stored .
DTC DETECTING CONDITION
 
ItemDetecting ConditionPossible cause
DTC Strategy
Manipulates Airfuel and stores the times it takes for the pre and post converter oxygen sensors to switch.
1.
Catalyst Converter
EnableConditions
Engine Runtime ≥ 580 sec.
Purge Concentration Learned
3 g/s ≤ Airflow ≤ 10 g/s
Throttle closed ≤ 1.5%
70°C(158 °F) ≤ Coolant Temp. ≤ 120°C(248 °F)
-7°C(19.4 °F) ≤ Ambient Temp. ≤ 105°C(221 °F)
Barometer ≥ 72 kPa
Max number of test attempts ≤ 12
Closed Loop
250°C( 482 °F) ≤ Catalyst Temp. ≤ 950°C(1742 °F)
Fuel learning completed
Vehicle speed ≤ 3 kph(1.8 mph)
Not airfuel ramping
Max idle time( about 60 sec.) not exceeded
No disabling faults present
No instrumentation slews active
Threshold value
Oxygen Storage Time < 1.2 sec.
Diagnosis Time
15 sec.
MIL On Condition
1 Driving cycle

 

MONITOR GDS DATA
1.
Connect GDS to Data Link Connector(DLC).
2.
IG “ON”.
3.
Select “DTC” button, and then Press “DTC Status” to check DTC’s information from the DTCs menu.
4.
Read “DTC Status” parameter.

img

5.
Is parameter displayed “Present fault”?
 

img

â–¶ Substitute with a known – good Catalyst Converter and check for proper operation.If the problem is corrected, Go to “Verification of Vehicle Repair” procedure.

img

â–¶ Go to “Component Inspection” procedure.
COMPONENT INSPECTION
â–  Monitor the Catalyst Converter
1.
Clear DTC.
2.
Start the engine and warm it up until the radiator fan comes on( more than at least 10 minutes).
3.
Drive at a steady speed between 45-55 mph(72-88 km/h) for 30 seconds.
4.
Stop and then maintain idle state for 120 seconds in D-position.
5.
Repeat step 3 once again.
6.
Stop and then keep it in idle state( D-positon) for 120 seconds.
7.
Repeat step 3 once again.
8.
Stop and then maintain idle state for 120 seconds in D-position.
9.
IG “OFF”
10.
Repeat steps 3 through 9 three times.
11.
Check if catalyst monitoring readiness is complete. so, if the readiness is incomplete, repeat steps 2 through 10.
12.
Does the scan tool show DTC P0420??
 

img

â–¶ Substitute with a known – good Catalyst Converter and check the signal waveform of HO2S for proper operation. If the problem is corrected, Go to “Verification of Vehicle Repair” procedure.

img

â–¶ It was intermittent failure.

New Videos on our YouTube Channel Every Week, Subscribe Now!

Related Posts

Shopping Cart
Scroll to Top