PZEV Engine
DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)CIRCUIT DESCRIPTION
DTC Detection Condition:
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
Monitor Result (Mode 06):
The ECM uses the air-fuel ratio (A/F) sensor and the heated oxygen sensor 2 to detect deterioration in the front catalyst.
In order to detect deterioration in the front catalyst, the ECM calculates Oxygen Storage Capacity (OSC) in the catalyst based on voltage output of the heated oxygen sensor 2 while performing the "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 driving 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 go LEAN or RICH by the ECM, and if a RICH and LEAN cycle of the heated oxygen sensor 2 is long, the OSC will become greater, and greater OSC basically capability of the catalyst are mutually related, the ECM judges if the catalyst has deteriorated based on the calculated OSC value.
CONFIRMATION DRIVING PATTERN FOR READINESS MONITOR
PURPOSE
HINT: Performing this confirmation pattern will activate the front catalyst monitoring by the ECM. This is very useful for verifying the completion of a repair.
a. Clear the DTCs.
1. Disconnect the battery terminal or remove the EFI and ETCS fuses for 60 seconds or more.
b. Connect the hand-held tester to the DLC3.
c. Enter the following menus: DIAGNOSIS / CARB OBD II / READINESS TESTS and 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 and check if any DTC (any pending code) is set.
If the READINESS CODE of "CAT EVAL" was "INCMPL" and any DTC (include pending codes) was not set, extend the driving time.
NOTE: If you do not have the hand-held tester, perform again the same confirmation driving pattern after turning off the ignition switch upon finishing the first confirmation driving pattern.
CONDITIONING THE A/F SENSOR AND HEATED OXYGEN SENSOR 2 FOR TESTING
HINT: Follow this engine rpm and timing pattern to properly activate and condition these sensors prior to the observation of their output waveforms.
a. Connect the hand-held tester or the OBD II scan tool to the DLC3.
b. Start the engine and warm it up with all the accessories switched OFF until the coolant temperature is stable.
c. Run the engine at 2,500 to 3,000 rpm for about 3 minutes.
d. When running the engine at 3,000 rpm for 2 seconds and 2,000 rpm for 2 seconds, check the waveforms of the A/F sensor and heated oxygen sensor 2.
HINT: If either output of the A/F sensor and the heated oxygen sensor 2 does not fluctuate or has noise, the sensor may be malfunctioning.
If voltage outputs of both the sensors remain at LEAN or RICH, the air-fuel ratio may be extremely LEAN or RICH. In such case, perform the following A/F CONTROL in ACTIVE TEST with the hand-held tester. If the catalyst has deteriorated, the voltage output of the heated oxygen sensor 2 (located after the front catalyst) fluctuates up and down extensively even under normal driving ("active air-fuel ratio control" is not performed).
PERFORM A/F CONTROL
HINT:
Hand-held tester only:
Narrowing down the trouble area is possible by performing the "A/F CONTROL" ACTIVE TEST (A/F sensor, heated oxygen sensor 2 or other trouble areas can be distinguished).
a. Perform ACTIVE TEST using the hand-held tester (A/F CONTROL).
HINT: "A/F CONTROL" is an ACTIVE TEST which changes the injection volume -12.5 % or +25 %.
1. Connect the hand-held tester to the DLC3 on the vehicle.
2. Turn the ignition switch ON.
3. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
4. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. Perform "A/F CONTROL" 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 2 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: There is a few seconds delay in the A/F sensor output and there is about 20 seconds delay in the heated oxygen sensor 2 output.
The following A/F CONTROL procedure enables to technician to check and graph the voltage outputs of both the A/F Sensor and Heated Oxygen Sensor 2.
For displaying the graph indication, enter "DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA", then select "AFS B1S1 and O2S B1S2" by pressing "YES" button and push "ENTER" button before pressing "F4" button.
Step 1 - 4:
INSPECTION PROCEDURE
HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.