2UZ-FE ENGINE CONTROL: SFI SYSTEM: MONITOR DESCRIPTION (2008 Sequoia)

Last Modified: 11-29-2007		1.6 C
Service Category: Engine/Hybrid System	Section: Engine Control
Model Year: 2008	Model: Sequoia	Doc ID: RM000000TMD03PX
Title: 2UZ-FE ENGINE CONTROL: SFI SYSTEM: MONITOR DESCRIPTION (2008 Sequoia)

DTC

P0420

Catalyst System Efficiency Below Threshold (Bank 1)

DTC

P0430

Catalyst System Efficiency Below Threshold (Bank 2)

MONITOR DESCRIPTION

The ECM uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency.

The first sensor, the Air-Fuel Ratio (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air-fuel ratio control.

The OSC value is an indication of the oxygen storage capacity of the TWC. When the vehicle is being driven with a warm engine, active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the ECM deliberately sets the air-fuel ratio to lean or rich levels. If the rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.

The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and stores the DTC.

DTC No.

DTC Detection Condition

Trouble Area

P0420

OSC value smaller than standard value under active air-fuel ratio control

(2 trip detection logic)

Exhaust front pipe assembly No. 2 (with TWC)
Gas leak from exhaust system
Air-Fuel Ratio (A/F) sensor (for bank 1 sensor 1)
Heated Oxygen (HO2) sensor (for bank 1 sensor 2)

P0430

OSC value smaller than standard value under active air-fuel ratio control

(2 trip detection logic)

Exhaust pipe assembly front (with TWC)
Gas leak from exhaust system
Air-Fuel Ratio (A/F) sensor (for bank 2 sensor 1)
Heated Oxygen (HO2) sensor (for bank 2 sensor 2)

HINT:

Bank 1 refers to the bank that includes No. 1 cylinder.
Bank 2 refers to the bank that does not include No. 1 cylinder.
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR STRATEGY

Related DTCs	P0420: Catalyst Deterioration (bank 1) P0430: Catalyst Deterioration (bank 2)
Required Sensors/Components (Main)	A/F sensor and HO2 sensor
Required Sensors/Components (Related)	Intake air temperature sensor, mass air flow meter, crankshaft position sensor and engine coolant temperature sensor
Frequency of Operation	Once per driving cycle
Duration	About 30 seconds
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever following DTCs not present	P0011 (VVT System 1 - Advance) P0012 (VVT System 1 - Retard) P0021 (VVT System 2 - Advance) P0022 (VVT System 2 - Retard) P0031, P0032, P0051, P0052 (A/F Sensor Heater - Sensor 1) P0037, P0038, P0057, P0058 (O2 Sensor Heater - Sensor 2) P0102 - P0103 (MAF meter) P0115 - P0118 (ECT sensor) P0120 - P0223, P2135 (TP sensor) P0125 (Insufficient ECT for Closed Loop) P0136, P0156 (O2 Sensor - Sensor 2) P0171, P0172 (Fuel system) P0300 - P0308 (Misfire) P0335 (CKP sensor) P0351 - P0358 (Igniter) P0500 (VSS) P2196, P2198 (A/F sensor - rationality) P2237, P2240 (A/F sensor - open) P2440 (AIR control valve stuck open) P2441 (AIR control valve stuck close) P2444 (AIP stuck On) P2445 (AIP stuck Off) P2A00, P2A03 (A/F sensor - slow response)
Battery voltage	11 V or more
Intake air temperature	-10°C (14°F) or more
Engine coolant temperature	75°C (167°F) or more
Atmospheric pressure	76 kPa (570 mmHg) or more
Idling	OFF
Engine RPM	Less than 3200 rpm
A/F sensor status	Activated
Fuel system status	Closed loop
Engine load	10 to 70%
All of following conditions (a), (b) and (c) met	-
(a) Mass air flow rate	6 to 75 g/sec.
(b) Estimated front catalyst temperature	620 to 830°C (1148 to 1526°F)
(c) Estimated rear catalyst temperature	410 to 830°C (770 to 1526°F)
Rear HO2 sensor heater monitor	Completed
Shift position	4th or higher

TYPICAL MALFUNCTION THRESHOLDS

Oxygen Storage Capacity (OSC) of Three-Way Catalytic Converter (TWC)

Less than 0.12 g

MONITOR RESULT

Refer to Checking Monitor Status .

CONFIRMATION DRIVING PATTERN

HINT:

Performing this confirmation pattern will activate the catalyst monitor. This is very useful for verifying the completion of a repair.

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Clear DTCs (if set) .

(e) Enter the following menus: Powertrain / Engine / Data List / All / Catalyst Monitor CMPL.

(f) Check that Catalyst Monitor CMPL is Incomplete.

(g) Start the engine and warm it up.

(h) Drive the vehicle at between 64 km/h and 113 km/h (40 mph and 70 mph) for at least 10 minutes.

(i) Note the state of the Readiness Tests items. Those items will change to Complete as Catalyst Monitor CMPL monitor operates.

(j) Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.

(k) Check if any DTCs (any pending DTCs) are output.

HINT:

If CAT Catalyst Monitor CMPL does not change to Complete, and any pending DTCs fail to set, extend the driving time.

CONDITIONING FOR SENSOR TESTING

HINT:

Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

(a) Connect the Techstream to the DLC3.

(b) Start the engine and warm it up with all the accessories switched OFF until the engine coolant temperature stabilizes.

(d) While running the engine at 3000 rpm and 2000 rpm at 2 second intervals, check the waveforms of the A/F and HO2 sensors using the Techstream.

HINT:

If either voltage output of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) sensor does not fluctuate, or there is a noise in the waveform of either sensor, the sensor may be malfunctioning.
If the voltage outputs of both the sensors remain lean or rich, the air-fuel ratio may be extremely lean or rich. In such cases, perform the following Control the Injection Volume for A/F Sensor using the Techstream.
If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).

INSPECTION PROCEDURE

HINT:

Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 OR P0430)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read DTCs.

Result

Result	Proceed to
P0420 or P0430 is output	A
P0420 or P0430 and other DTCs are output	B

HINT:

If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

2.	PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL)

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

(d) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

(e) On the Techstream, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

(f) Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

(g) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the Techstream.

Standard:

A/F sensor reacts in accordance with increases and decreases in fuel injection volume:

+25% = Rich output:

Less than 3.0 V

-12.5% = Lean output:

More than 3.35 V

NOTICE:

The A/F sensor has an output delay of a few seconds and the HO2 sensor has a maximum output delay of approximately 20 seconds.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1			-
2			A/F sensor A/F sensor heater A/F sensor circuit
3			HO2 sensor HO2 sensor heater HO2 sensor circuit
4			Injector Fuel pressure Gas leak from exhaust system (Air-fuel ratio extremely rich or lean)

Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

To display the graph on the Techstream, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/ F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2, then press the graph button on the Data List view.

Result

Result	Proceed to
Case 1	A
Case 2	B
Case 3	C
Case 4	D

3.	INSPECT FOR EXHAUST GAS LEAK

OK:

No gas leak.

4.	CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)

(a) According to the DTCs output in step 1 (Check any other DTCS output), proceed to the next step, referring to the table below.

Result

Result	Proceed to
P0420	A
P0430	B
P0420 and P0430	A and B

5.	REPLACE EXHAUST FRONT PIPE ASSEMBLY NO.2

(a) Replace the exhaust front pipe assembly No. 2 .

6.	REPLACE EXHAUST PIPE ASSEMBLY FRONT

(a) Replace the exhaust pipe assembly front .

7.	CHECK FOR EXHAUST GAS LEAK

OK:

No gas leak.