INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)
INSPECT INTEGRATION RELAY (EFI MAIN RELAY)
CHECK HARNESS AND CONNECTOR (HO2 SENSOR - INTEGRATION RELAY)
CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
CHECK WHETHER DTC OUTPUT RECURS
DTC P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2) |
DTC P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2) |
DESCRIPTION
- Refer to DTC P0136 (RAV4_ACA30 RM000000WBY0CCX_01.html).
- HINT:
- Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
- When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the Heated Oxygen (HO2) 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 HO2 sensor heater circuit uses a relay on the +B side of the circuit.
| DTC No. | DTC Detection Condition | Trouble Area |
| P0037 | Heated Oxygen (HO2) sensor heater current less than 0.3 A (1 trip detection logic) |
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| P0038 | Heated Oxygen (HO2) sensor heater current more than 2 A (1 trip detection logic) |
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MONITOR DESCRIPTION
The sensing portion of the Heated Oxygen (HO2) sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.- Heated oxygen sensor heater range check (P0037 and P0038):
The ECM monitors the current applied to the O2 sensor heater to check the heater for malfunctions. If the current is below the threshold value, the ECM determines that there is an open circuit in the heater. If the current is above the threshold value, the ECM determines that there is a short circuit in the heater.
The ECM constantly monitors the current applied to the heater. If the ECM detects an open or short circuit, the ECM turns the MIL on and sets a DTC.
If a malfunction is detected, the ECM cuts off the current applied to the heater.
Example:
The ECM sets DTC P0038 when the current in the HO2 sensor heater is more than 2 A. Conversely, when the heater current is less than 0.3 A, DTC P0037 is set.
WIRING DIAGRAM
Refer to DTC P2195 (RAV4_ACA30 RM000000WC40H1X_07.html).CONFIRMATION DRIVING PATTERN
These DTCs are detected when the engine idles for 110 seconds or more.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.
| 1.INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE) |
Inspect the heated oxygen sensor (RAV4_ACA30 RM000001Z1X00TX_01_0001.html).
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| OK | |
| 2.CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR) |
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Disconnect the HO2 sensor connector.
Turn the ignition switch on (IG).
Measure the voltage according to the value(s) in the table below.
- Standard voltage:
Tester Connection Switch Condition Specified Condition B19-2 (+B) - Body ground Ignition switch on 11 to 14 V
Text in Illustration *a Front view of wire harness connector
(to Heated Oxygen Sensor)
Reconnect the HO2 sensor connector.
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| NG | |
| 3.INSPECT INTEGRATION RELAY (EFI MAIN RELAY) |
Remove the integration relay from the engine room relay block.
Inspect the EFI MAIN fuse.
Remove the EFI MAIN fuse from the integration relay.
Measure the EFI MAIN fuse resistance.
- Standard resistance:
- Below 1 Ω
Reinstall the EFI MAIN fuse.
Inspect the EFI MAIN relay.
Measure the EFI MAIN relay resistance.
- Standard resistance:
Tester Connection Specified Condition 1C-1 - 1A-4 10 kΩ or higher Below 1 Ω
(Apply battery voltage between terminals 1A-2 and 1A-3)
Reinstall the integration relay.
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| OK | |
| 4.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - INTEGRATION RELAY) |
Disconnect the HO2 sensor connector.
Remove the integration relay from the engine room No. 1 relay block.
Measure the resistance according to the value(s) in the table below.
- Standard resistance (Check for open):
Tester Connection Condition Specified Condition B19-2 (+B) - 1A-4 Always Below 1 Ω
- Standard resistance (Check for short):
Tester Connection Condition Specified Condition B19-2 (+B) or 1A-4 - Body ground Always 10 kΩ or higher
Reconnect the HO2 sensor connector.
Reinstall the integration relay.
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| OK | ||
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| 5.CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM) |
Disconnect the HO2 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 B19-1 (HT1B) - B32-47 (HT1B) Always Below 1 Ω
- Standard resistance (Check for short):
Tester Connection Condition Specified Condition B19-1 (HT1B) or B32-47 (HT1B) - Body ground Always 10 kΩ or higher
Reconnect the HO2 sensor connector.
Reconnect the ECM connector.
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| OK | |
| 6.CHECK WHETHER DTC OUTPUT RECURS |
Connect the intelligent tester to the DLC3.
Turn the ignition switch on (IG).
Turn the tester ON.
Clear DTCs (RAV4_ACA30 RM000000PDK0AJX.html).
Start the engine.
Allow the engine to idle for 2 minutes or more.
Select the following menu items: Powertrain / Engine and ECT / DTC.
Read DTCs.
Result Result Proceed to DTC is not output A DTC P0037 or P0038 is output B
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| A | ||
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