Brand:
Toyota
Model Name:
4Runner GRN210 215 UZN210 215
Manual:
Repair Manual
Section:
2Uz-Fe Engine Control System
Title:
Sfi System
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)
DESCRIPTION
Refer to DTC P2195 (Click here).- HINT:
- Although the DTC titles refer to the "oxygen sensor", these DTCs relate to the Air Fuel Ratio (A/F) sensor.
- 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 more than 19.7 A (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 will be inaccurate. As a result, the ECM will be 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 sets a DTC.
MONITOR STRATEGY
| Related DTCs | P0031: A/F sensor heater (bank 1) range check (low current) P0032: A/F sensor heater (bank 1) range check (high current) P0051: A/F sensor heater (bank 2) range check (low current) P0052: A/F sensor heater (bank 2) range check (high 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
| Monitor runs whenever following DTCs not present | None |
| Battery voltage | 10.5 V or more |
| A/F sensor heater duty ratio | 50 % or more |
| Time after engine start | 10 seconds or more |
| Time after engine start | 10 seconds or more |
TYPICAL MALFUNCTION THRESHOLDS
| A/F sensor heater current | Less than 0.8 A |
| A/F sensor heater current | More than 10 A |
COMPONENT OPERATING RANGE
| A/F sensor heater current | 1.8 to 3.4 A at 20°C (68°F) |
MONITOR RESULT
Refer to CHECKING MONITOR STATUS (Click here) for detailed information.The test value and test limit information are described as shown in the following table. Check the monitor result and test values after performing the monitor drive pattern (Click here).
- TID (Test Identification Data) is assigned to each emissions-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit. - CID (Component Identification Data) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD II scan tools.
WIRING DIAGRAM
Refer to DTC P2195 (Click here).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.
1.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
Disconnect the A12 and A13 Air Fuel Ratio (A/F) sensor connectors.
Measure the resistance of the A/F sensor connectors.
- Standard resistance:
Tester Connection Specified Condition HT (1) - +B (2) 1.8 Ω to 3.4 Ω at 20°C (68°F) HT (1) - AF- (4) 10 kΩ or higher
Reconnect the A/F sensor connectors.
| REPLACE AIR FUEL RATIO SENSOR | |||
| OK | |
 |
2.INSPECT A/F RELAY
Remove the A/F relay from the engine room R/B.
Measure the resistance of the A/F relay.
- Standard resistance:
Tester Connection Specified Condition 3 - 5 10 kΩ or higher 3 - 5 Below 1 Ω
(when battery voltage applied to terminals 1 and 2)
Reinstall the A/F relay.
| REPLACE A/F RELAY | |||
| OK | |
|
3.INSPECT ECM (HA1A OR HA2A VOLTAGE)
Turn the ignition switch ON.
Measure the voltage of the E5 ECM connector.
- Standard voltage:
Tester Connection Specified Condition HA1A (E5-2) - Body ground 9 to 14 V HA2A (E5-1) - Body ground
- HINT:
- The HA1A means the A/F sensor bank 1 sensor 1.
- The HA2A means the A/F sensor bank 2 sensor 1.
| REPLACE ECM | |||
| NG | |
|
4.CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM, A/F SENSOR - A/F RELAY)
Turn the ignition switch OFF.
Disconnect the A12 or A13 A/F sensor connector.
Disconnect the E5 ECM connector.
Measure the resistance.
- Standard resistance (Check for open):
Tester Connection Specified Condition HT (A12-1) - HA1A (E5-2) Below 1 Ω HT (A13-1) - HA2A (E5-1)
- Standard resistance (Check for short):
Tester Connection Specified Condition HT (A12-1) or HA1A (E5-2) - Body ground 10 kΩ or higher HT (A13-1) or HA2A (E5-1) - Body ground
Remove A/F relay from engine room R/B.
Measure the resistance.
- Standard resistance (Check for open):
Tester Connection Specified Condition +B (A12-2) - A/F relay (3) Below 1 Ω +B (A13-2) - A/F relay (3)
- Standard resistance (Check for short):
Tester Connection Specified Condition +B (A12-2) or A/F relay (3) - Body ground 10 kΩ or higher +B (A13-2) or A/F relay (3) - Body ground
Reinstall the A/F relay from engine room R/B.
Reconnect the ECM connector.
Reconnect the A/F sensor connectors.
| REPAIR OR REPLACE HARNESS OR CONNECTOR | |||
| OK | |
 | |
| CHECK FOR INTERMITTENT PROBLEMS | |