P0141
2TR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0037,P0038,P0141: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
CAUTION / NOTICE / HINT
DESCRIPTION
Refer to DTC P0136 P0136.
HINT
- Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
- When either of these DTCs is 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 to 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.
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 concentration 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.
Heated oxygen sensor heater performance (P0141):
- After the accumulated heater ON time exceeds 100 seconds, the ECM calculates the heater resistance using the battery voltage and the current applied to the heater.
- If the resistance is above the threshold value, the ECM determines that there is a malfunction in the HO2 sensor heater and sets DTC P0141.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
P0037:
P0038 Case 1:
P0038 Case 2:
P0141
TYPICAL MALFUNCTION THRESHOLDS
P0037:
P0038:
P0141:
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data
WIRING DIAGRAM
Refer to DTC P0136 P0136.
INSPECTION PROCEDURE
HINT
- If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
- 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 HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Disconnect the H3 Heated Oxygen (HO2) sensor connector.
(b) Measure the resistance between the terminals of the HO2 sensor connector.
Standard Resistance:
(c) Reconnect the HO2 sensor connector.
NG -- REPLACE HEATED OXYGEN SENSOR Removal
OK -- Continue to next step.
2. INSPECT EFI RELAY
(a) Remove the EFI relay from the engine room R/B.
(b) Check the EFI relay resistance.
Standard Resistance:
(c) Reinstall the EFI relay.
NG -- REPLACE EFI RELAY
OK -- Continue to next step.
3. INSPECT ECM (HT1B VOLTAGE)
(a) Turn the ignition switch to ON.
(b) Measure the voltage between the terminals of the ECM connectors.
Standard Voltage:
OK -- REPLACE ECM Removal
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM, HEATED OXYGEN SENSOR - EFI RELAY)
(a) Check the harness and connectors between the ECM and HO2 sensor.
(1) Disconnect the H3 HO2 sensor connector.
(2) Disconnect the E4 ECM connector.
(3) Check the resistance.
Standard Resistance (Check for open)::
Standard Resistance (Check for short):
(4) Reconnect the HO2 sensor connector.
(5) Reconnect the ECM connector.
(b) Check the harness and connector between the HO2 sensor and EFI relay.
(1) Inspect the EFI No. 2 fuse.
### ptxt ### Remove the EFI No. 2 fuse from the engine room R/B.
### ptxt ### Check the EFI No. 2 fuse resistance.
Standard Resistance:
Below 1 Ohms
### ptxt ### Reinstall the EFI No. 2 fuse.
(2) Disconnect the H3 HO2 sensor connector.
(3) Remove the EFI relay from the engine room R/B.
(4) Check the resistance.
Standard Resistance (Check for open):
Standard Resistance (Check for short):
(5) Reconnect the HO2 sensor connector.
(6) Reinstall the EFI relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM Removal