INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
CHECK TERMINAL VOLTAGE (POWER SOURCE)
CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032 OR P101D)
INSPECT AIR FUEL RATIO SENSOR HEATER RELAY (A/F)
CHECK HARNESS AND CONNECTOR (A/F SENSOR - A/F RELAY, A/F RELAY - INTEGRATION RELAY)
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 P101D A/F Sensor Heater Circuit Performance Bank 1 Sensor 1 Stuck ON |
DESCRIPTION
Refer to DTC P2195 (HILUX_TGN26 RM000000WC40R3X_01.html).- HINT:
- When any of these DTCs is stored, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe mode. The ECM continues operating in fail-safe mode until the ignition switch is turned off.
- Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
- The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.
| DTC No. | DTC Detection Condition | Trouble Area |
| P0031 | The heater current is below the specified value while the heater is operating (1 trip detection logic). |
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| P0032 | An air fuel ratio sensor heater current failure (1 trip detection logic). |
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| P101D | The heater current is higher than the specified value while the heater is not operating (1 trip detection logic). | ECM |
- HINT:
- 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 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 air fuel ratio 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 air fuel ratio 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 air fuel ratio sensor becomes inaccurate. As a result, the ECM is unable to regulate the air-fuel ratio properly.
When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.
WIRING DIAGRAM
Refer to DTC P2195 (HILUX_TGN26 RM000000WC40R3X_07.html).INSPECTION PROCEDURE
- NOTICE:
- Inspect the fuses of circuits related to this system before performing the following inspection procedure.
- HINT:
- Read freeze frame data using the intelligent tester. 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.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
| 1.INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) |
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Disconnect the air fuel ratio sensor connector.
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) 1.6 to 3.2 Ω 1 (HA1A) - 4 (A1A-) Always 10 kΩ or higher
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| OK | |
| 2.CHECK TERMINAL VOLTAGE (POWER SOURCE) |
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Disconnect the air fuel ratio sensor connector.
Turn the ignition switch to ON.
Measure the voltage according to the value(s) in the table below.
- Standard Voltage:
Tester Connection Switch Condition Specified Condition C85-2 (+B) - Body ground Ignition switch ON 11 to 14 V
Text in Illustration *a Front view of wire harness connector
(to Air Fuel Ratio Sensor)
Reconnect the air fuel ratio sensor connector.
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| OK | |
| 3.CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM) |
Disconnect the air fuel ratio sensor connector.
Disconnect the ECM connector.
Measure the resistance according to the value(s) in the table below.
- Standard Resistance (Check for Open):
Tester Connection Condition Specified Condition C85-1 (HA1A) - C97-6 (HA1A) Always Below 1 Ω
- Standard Resistance (Check for Short):
Tester Connection Condition Specified Condition C85-1 (HA1A) or C97-6 (HA1A) - Body ground Always 10 kΩ or higher
Reconnect the air fuel ratio sensor connector.
Reconnect the ECM connector.
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| OK | |
| 4.CHECK WHETHER DTC OUTPUT RECURS (DTC P0031, P0032 OR P101D) |
Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the intelligent tester on.
Clear DTCs (HILUX_TGN26 RM000000PDK12LX.html).
Start the engine.
Allow the engine to idle for 1 minute or more.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
Read DTCs.
Result Result Proceed to DTC is not output A DTC P0031, P0032 or P101D is output B
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| A | ||
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| 5.INSPECT AIR FUEL RATIO SENSOR HEATER RELAY (A/F) |
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Inspect the A/F relay.
Remove the A/F relay from the engine room relay block.
Measure the resistance according to the value(s) in the table below.
- Standard Resistance:
Tester Connection Condition Specified Condition 3 - 5 Always 10 kΩ or higher 3 - 5 Always Below 1 Ω
(when battery voltage is applied to terminals 1 and 2)
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| OK | |
| 6.CHECK HARNESS AND CONNECTOR (A/F SENSOR - A/F RELAY, A/F RELAY - INTEGRATION RELAY) |
Disconnect the air fuel ratio sensor connector.
Remove the A/F relay from the engine room relay block.
Remove the integration relay from the engine room relay block.
Measure the resistance according to the value(s) in the table below.
- Standard Resistance (Check for Open):
Tester Connection Condition Specified Condition C85-2 (+B) - A/F relay terminal (3) Always Below 1 Ω A/F relay terminal (5) - 1H-1 Always Below 1 Ω
- Standard Resistance (Check for Short):
Tester Connection Condition Specified Condition C85-2 (+B) or A/F relay terminal (3) - Body ground Always 10 kΩ or higher A/F relay terminal (5) or 1H-1 - Body ground Always 10 kΩ or higher
Reconnect the air fuel ratio sensor connector.
Reinstall the integration relay.
Reinstall the A/F relay.
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| OK | ||
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