- Open in A/F sensor heater circuit
- A/F sensor heater (for sensor 1)
- Integration relay
- ECM
| Last Modified: 11-29-2007 | 1.6 C | |
| Service Category: Engine/Hybrid System | Section: Engine Control | |
| Model Year: 2008 | Model: Sequoia | Doc ID: RM000000WC1067X |
| Title: 2UZ-FE ENGINE CONTROL: SFI SYSTEM: CAUTION / NOTICE / HINT (2008 Sequoia) | ||
|
DTC |
P0031 |
Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1) |
|
DTC |
P0032 |
Oxygen (A/F) Sensor Heater Control Circuit High (Bank 1 Sensor 1) |
|
DTC |
P0051 |
Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 2 Sensor 1) |
|
DTC |
P0052 |
Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1) |
CAUTION / NOTICE / HINT
DESCRIPTION
Refer to DTC P2195
.
HINT:
- Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
- When one of these DTCs is stored, the ECM enters fail-safe mode. The ECM turns off the A/F sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned off.
-
The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The A/F sensor heater circuit uses a relay on the +B side of the circuit.
|
DTC No. |
DTC Detection Condition |
Trouble Area |
|---|---|---|
|
P0031 P0051 |
Air-Fuel Ratio (A/F) sensor heater current less than 0.8 A (1 trip detection logic) |
|
|
P0032 P0052 |
Air-Fuel Ratio (A/F) sensor heater current fail (1 trip detection logic) |
|
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 DESCRIPTION
The ECM uses information from the Air-Fuel Ratio (A/F) sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the Three-Way Catalytic Converter (TWC) to purify the exhaust gases.
The A/F sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum coated zirconia and includes an integrated heating element.
The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.
The A/F sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates the supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the A/F sensor becomes inaccurate. As a result, the ECM is unable to regulate air-fuel ratio properly.
When the current in the A/F sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.
MONITOR STRATEGY
|
Related DTCs |
P0031: A/F sensor heater (bank 1) open/short (Low electrical current) P0032: A/F sensor heater (bank 1) open/short (High electrical current) P0051: A/F sensor heater (bank 2) open/short (Low electrical current) P0052: A/F sensor heater (bank 2) open/short (High electrical current) |
|
Required Sensors/Components (Main) |
A/F sensor heater |
|
Required Sensors/Components (Related) |
- |
|
Frequency of Operation |
Continuous |
|
Duration |
10 seconds |
|
MIL Operation |
Immediate |
|
Sequence of Operation |
None |
TYPICAL ENABLING CONDITIONS
All
|
Monitor runs whenever following DTCs not present |
P0300-P0308 (Misfire) |
P0031 and P0051
|
Battery voltage |
10.5 V or more |
|
A/F sensor heater duty-cycle ratio |
50% or more |
|
Time after engine start |
10 seconds or more |
P0032 and P0052
|
Engine |
Running |
TYPICAL MALFUNCTION THRESHOLDS
P0031 and P0051
|
A/F sensor heater current |
Less than 0.8 A |
P0032 and P0052
|
Hybrid IC high current limiter port |
Fail |
COMPONENT OPERATING RANGE
|
A/F sensor heater resistance |
1.8 to 3.4 Ω at 20 °C (68 °F) |
WIRING DIAGRAM
Refer to DTC P2195
.
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. |
INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) |
(a) Disconnect the A/F sensor connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
1 (HA1A) - 2 (+B) |
20°C (68°F) |
1.8 to 3.4 Ω |
|
1 (HA1A) - 4 (A1A-) |
Always |
10 kΩ or higher |
|
1 (HA2A) - 2 (+B) |
20°C (68°F) |
1.8 to 3.4 Ω |
|
1 (HA2A) - 4 (A2A-) |
Always |
10 kΩ or higher |
|
|
2. |
CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR) |
(a) Disconnect the A/F sensor connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
|
Tester Connection |
Switch Condition |
Specified Condition |
|---|---|---|
|
D19-2 (+B) - Body ground |
Ignition switch ON |
11 to 14 V |
|
D20-2 (+B) - Body ground |
Ignition switch ON |
11 to 14 V |
Result
|
Result |
Proceed to |
|---|---|
|
Outside standard range |
A |
|
Within standard range |
B |
|
|
3. |
INSPECT INTEGRATION RELAY (A/F) |
(a) Remove the integration relay from the engine room relay block.
(b) Inspect the A/F fuse.
(1) Remove the A/F fuse from the integration relay.
(2) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
A/F fuse |
Always |
Below 1 Ω |
(3) Reinstall the A/F fuse.
(c) Inspect the integration relay (A/F).
(1) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
1C-1 - 1A-4 |
When battery voltage not applied |
10 kΩ or higher |
|
When battery voltage applied to terminals 1A-2 and 1A-3 |
Below 1 Ω |
|
|
4. |
CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - A/F SENSOR AND BODY GROUND) |
(a) Disconnect the A/F sensor connector.
(b) Remove the integration relay from the engine room relay block.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
D19-2 (+B) - 1A-4 |
Always |
Below 1 Ω |
|
D20-2 (+B) - 1A-4 |
Always |
Below 1 Ω |
|
1A-2 - 1B-5 |
Always |
Below 1 Ω |
|
1A-3 - Body ground |
Always |
Below 1 Ω |
|
D19-2 (+B) or 1A-4 - Body ground |
Always |
10 kΩ or higher |
|
D20-2 (+B) or 1A-4 - Body ground |
Always |
10 kΩ or higher |
|
1A-2 or 1B-5 - Body ground |
Always |
10 kΩ or higher |
|
|
9. |
CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) |
(a) Disconnect the A/F sensor connector.
(b) Disconnect the ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
|
Tester Connection |
Condition |
Specified Condition |
|---|---|---|
|
D19-1 (HA1A) - D56-22 (HA1A) |
Always |
Below 1 Ω |
|
D20-1 (HA2A) - D56-20 (HA2A) |
Always |
Below 1 Ω |
|
D19-1 (HA1A) or D56-22 (HA1A) - Body ground |
Always |
10 kΩ or higher |
|
D20-1 (HA2A) or D56-20 (HA2A) - Body ground |
Always |
10 kΩ or higher |
|
|
10. |
CHECK WHETHER DTC OUTPUT RECURS |
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream ON.
(d) Clear DTCs
.
(e) Start the engine.
(f) Allow the engine to idle for 1 minute or more.
(g) Enter the following menus: Powertrain / Engine / Trouble Codes.
(h) Read DTCs.
Result
|
Result |
Proceed to |
|---|---|
|
No DTC is output |
A |
|
P0031, P0032, P0051 or P0052 is output |
B |
|
|
|