P0161
2GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0037: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC P0037 - Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC P0038 - Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)
DTC P0057 - Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 2)
DTC P0058 - Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 2)
DTC P0141 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
DTC P0161 - Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
CAUTION / NOTICE / HINT
HINT: Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located furthest from the engine assembly.
DESCRIPTION
A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydro carbon (HC), and nitrogen oxides (NOx) into less harmful substances. To allow the TWC to function effectively, it is necessary to keep the air-fuel ratio of the engine near the stoichiometric air-fuel ratio. For helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen (HO2) sensor becomes used.
The HO2 sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).
When the air-fuel ratio becomes lean, the oxygen concentration in the exhaust gas becomes rich. The HO2 sensor informs the ECM that the post-TWC air-fuel ratio is lean (low voltage, i.e. less than 0.45 V).
Conversely, when the air-fuel ratio is richer than the stoichiometric air-fuel level, the oxygen concentration in the exhaust gas becomes lean. The HO2 sensor informs the ECM that the post-TWC air-fuel ratio is rich (high voltage, i.e. more than 0.45 V). The HO2 sensor has the property of changing its output voltage drastically when the air-fuel ratio is close to the stoichiometric level.
The ECM uses the supplementary information from the HO2 sensor to determine whether the air-fuel ratio after the TWC is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the HO2 sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air-fuel ratio control.
HINT: 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.
HINT:
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor furthest away from the engine assembly.
MONITOR DESCRIPTION
The sensing position 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, P0038, P0057 and P0058):
- 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 will determine that there is an open circuit in the heater. If the current is above the threshold value, the ECM will determine that there is a short circuit in the heater.
Example:
The ECM sets DTC P0038 or P0058 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 or P0057 is set.
Heated oxygen sensor heater performance (P0141 and P0161):
- 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 will determine that there is a malfunction in the HO2S heater and set DTC P0141 and P0161.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All:
P0037 and P0057:
P0038 and P0058 Case 1:
P0038 and P0058 Case 2:
P0141 and P0161:
TYPICAL MALFUNCTION THRESHOLDS
P0037 and P0057:
P0038 and P0058:
P0141 and P0161 (Heater performance monitor check):
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data.
WIRING DIAGRAM
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 Techstream. 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.
PROCEDURE
1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Disconnect the H14 heated oxygen (HO2) sensor connector (Bank 1 Sensor 2) or H9 heated oxygen sensor connector (Bank 2 Sensor 2).
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
Bank 1
Bank 2
(c) Reconnect the HO2 sensor connectors.
NG -- REPLACE HEATED OXYGEN SENSOR
OK -- Continue to next step.
2. CHECK TERMINAL VOLTAGE (+B OF SENSOR)
(a) Disconnect the H14 or H9 HO2 sensor connector.
(b) Turn the ignition switch to the ON position.
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:
(d) Reconnect the HO2 sensor connector.
OK -- CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
NG -- Continue to next step.
3. INSPECT FUSE (EFI NO. 2 FUSE)
(a) Remove the EFI No. 2 fuse from the engine room junction block.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
Below 1 Ohms
(c) Reinstall the EFI No. 2 fuse.
NG -- REPLACE EFI NO. 2 FUSE
OK -- Continue to next step.
4. INSPECT RELAY (EFI RELAY)
(a) Remove the EFI relay from the engine room junction block.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
(c) Reinstall the EFI relay.
NG -- REPLACE RELAY (EFI RELAY)
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (HO2 SENSOR - EFI RELAY)
5. CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
(a) Disconnect the H14 or H9 HO2 sensor connector.
(b) Disconnect the E9 and E10 ECM connectors.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance:
Check for open
Check for short
(d) Reconnect the ECM connectors.
(e) Reconnect the HO2 sensor connectors.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (HO2 SENSOR - ECM)
OK -- Continue to next step.
6. CHECK WHETHER DTC OUTPUT RECURS
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch to the ON position.
(c) Turn Techstream ON.
(d) Clear the DTCs DTC Check / Clear.
(e) Start the engine.
(f) Allow the engine to idle for 1 minute or more.
(g) Select the following menu items: Powertrain / Engine and ECT / Trouble Code.
(h) Read the DTCs.
Result:
B -- REPLACE ECM
A -- CHECK FOR INTERMITTENT PROBLEMS