P0420
DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1)MONITOR DESCRIPTION
DTC Detection Condition:
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
The ECM uses 2 sensors mounted before and after the three-way catalytic converter (TWC) to monitor its efficiency. The air-fuel ratio (A/F) sensor (sensor 1) sends pre-catalyst information to the ECM. The heated oxygen (O2) sensor (sensor 2) sends post-catalyst information to the ECM.
In order to detect deterioration in the catalyst, the ECM calculates Oxygen Storage Capacity (OSC) in the catalyst based on voltage output of sensor 2 while performing "active air-fuel ratio control" instead of the conventional detecting method which uses the locus ratio.
The OSC is an indication value of the catalyst oxygen storage capacity and is used for representing how much the catalyst can store oxygen. When the vehicle is being driven with a warm engine, the active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the air-fuel ratio is forcibly regulated to be LEAN or RICH by the ECM, and if a RICH and LEAN cycle of sensor 2 is long, the OSC will become greater. The greater OSC and capability of the catalyst are mutually related. The ECM judges if the catalyst has deteriorated based on the calculated OSC value. The ECM will illuminate the MIL and a DTC will be set.
HINT:
- Sensor 1 refers to the sensor mounted before the TWC and is located near the engine assembly.
- Sensor 2 refers to the sensor mounted after the TWC and is located far from the engine assembly.
MONITOR RESULT
Refer to detailed information. Checking Monitor Status
CONFIRMATION DRIVING PATTERN
HINT: Performing this confirmation pattern will activate the catalyst monitoring by the ECM. This is very useful for verifying the completion of repairs.
a. Clear the DTCs.
b. Connect the intelligent tester to the DLC3.
c. Enter the following menus: DIAGNOSIS / CARB OBD II / READINESS TESTS. Check that CAT EVAL is INCMPL (incomplete).
d. Drive the vehicle according to the confirmation driving pattern. Note the state of the Readiness Tests.
They will change to COMPL (complete) as the CAT evaluation monitors operate.
e. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
Check if any DTC (any pending code) is set.
If the READINESS CODE of CAT EVAL was INCMPL and any DTC (includes pending codes) was not set, extend the driving time.
NOTE: If you do not have the intelligent tester, perform again the same confirmation driving pattern after turning OFF the power switch upon finishing the first confirmation driving pattern.
CONDITIONING FOR SENSOR TESTING
a. Connect the intelligent tester to the DLC3.
b. Put the engine in inspection mode.
c. Start the engine and warm it up with all the accessories switched OFF until the engine coolant temperature becomes stable.
d. Run the engine at 2,500 rpm for approximately 3 minutes.
e. Run the engine at 2,500 rpm for 2 seconds and then 1,500 rpm for 2 seconds.
f. Check the waveform of the oxygen sensor (sensor 2).
HINT: If output of the A/F sensor or the heated oxygen sensor does not fluctuate or has noise, the sensor may be malfunctioning.
If voltage output of both sensors remain at LEAN or RICH, the air-fuel ratio may be extremely LEAN or RICH. In such a case, perform the following A/F CONTROL operation in ACTIVE TEST using the intelligent tester. If the catalyst has deteriorated, the voltage output of the heated oxygen sensor fluctuates up and down widely even under normal driving ("active air-fuel ratio control" is not performed).
INSPECTION PROCEDURE
HINT:
- Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
- Malfunctioning areas can be found by performing the ACTIVE TEST / A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble area are malfunctioning or not.
a. Perform the ACTIVE TEST A/F CONTROL operation.
- The A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.
1. Connect the intelligent tester to the DLC3.
2. Turn the power switch ON (IG).
3. Put the engine in inspection mode.
4. Warm up the engine by running the engine at 2,500 rpm, depressing the accelerator pedal more than 60% for approximately 90 seconds.
5. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
6. Perform the A/F CONTROL operation with the engine in an idle condition (press the right or left button).
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25% --> rich output: Less than 3.0 V
-12.5% --> lean output: More than 3.35 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25% --> rich output: More than 0.55 V
-12.5% --> lean output: Less than 0.4 V
NOTE: The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.
The following A/F CONTROL procedure enables the technician to check and graph the voltage output of both A/F sensor and heated oxygen sensor.
To display the graph, enter ACTIVE TEST / A/F CONTROL / USER DATA, select "AFS B1S1 and O2S B1S2" by pressing the "YES" button followed by the "ENTER" button and then press the "F4" button.
Step 1:
