P0038
2GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0037,P0038,P0057,P0058,P0141,P0161: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
P0161 - Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
DESCRIPTION
A three-way catalytic converter (TWC) is used in order to convert the carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (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 the purpose of helping the ECM to deliver accurate air-fuel ratio control, a Heated Oxygen (HO2) sensor is 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
- 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 engine 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.
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 farthest 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 HO2 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 fail. 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:
All::
P0037 and P0057:
P0037 and P0057::
P0038 and P0058 (Case 1):
P0038 and P0058 (Case 1)::
P0038 and P0058 (Case 2):
P0038 and P0058 (Case 2)::
P0141 and P0161:
P0141 and P0161::
TYPICAL MALFUNCTION THRESHOLDS
P0037 and P0057:
P0037 and P0057::
P0038 and P0058:
P0038 and P0058::
P0141 and P0161 (Heater performance monitor check):
P0141 and P0161 (Heater performance monitor check)::
COMPONENT OPERATING RANGE
MONITOR RESULT
- Refer to CHECKING MONITOR STATUS Checking Monitor Status.
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the engine switch on (IG) and turn the Techstream on.
- Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) DTC Check / Clear.
- Turn the engine switch off and wait for 30 seconds.
- Turn the engine switch on (IG) and turn the Techstream on [A].
- Start the engine and idle it for 5 minutes or more [B].
- With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].
- Idle the engine for 5 minutes or more [D].
- Enter the following menus: Powertrain / Engine / Trouble Codes / Pending.
- Read the pending DTC [E].
- If a pending DTC is output, the system is malfunctioning.
HINT
If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.
- Input the DTC: P0037, P0038, P0057, P0058, P0141 or P0161.
- Check the DTC judgment result.
HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows NORMAL, the system is normal.
- If the judgment result shows INCOMPLETE or UNKNOWN, perform step [B] through [D] again.
- Enter the following menus: Powertrain / Engine / Utility / All Readiness.
- Check the judgment result.
HINT
- If the judgment result shows ABNORMAL, the system has a malfunction.
- If the judgment result shows NORMAL, the system is normal.
- If the test result is INCOMPLETE or UNKNOWN and no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.
HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.
WIRING DIAGRAM
Refer to DTC P0136 P0136.
INSPECTION PROCEDURE
HINT
Read freeze frame data using the 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 Freeze Frame Data.
PROCEDURE
1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Disconnect the B24 heated oxygen sensor connector (Bank 1 Sensor 2) or B25 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 sensor 2):
Standard resistance (Bank 2 sensor 2):
(c) Reconnect the HO2 sensor connector.
NG -- REPLACE HEATED OXYGEN SENSOR Removal
OK -- Continue to next step.
2. CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)
(a) Disconnect the B24 heated oxygen sensor connector (Bank 1 Sensor 2) or B25 heated oxygen sensor connector (Bank 2 Sensor 2).
(b) Turn the engine switch on (IG).
(c) Measure the voltage between the terminals.
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. 3)
(a) Remove the EFI No. 3 fuse from the engine room R/B.
(b) Measure the EFI No. 3 fuse resistance.
Standard resistance:
Below 1 Ohms
(c) Reinstall the EFI No. 3 fuse.
NG -- REPLACE EFI NO. 3 FUSE
OK -- Continue to next step.
4. INSPECT ENGINE ROOM JUNCTION BLOCK
(a) Remove the engine room junction block from the engine room R/B.
(b) Inspect the EFI relay.
(1) Measure the EFI relay resistance.
Standard resistance:
(c) Reinstall the engine room junction block.
NG -- REPLACE ENGINE ROOM JUNCTION BLOCK
OK -- Continue to next step.
5. INSPECT FUSE (EFI MAIN)
(a) Remove the EFI MAIN fuse from the engine room R/B.
(b) Measure the EFI MAIN fuse.
Standard resistance:
Below 1 Ohms
(c) Reinstall the EFI MAIN fuse.
NG -- REPLACE EFI MAIN FUSE
OK -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (HO2 SENSOR - EFI RELAY)
(a) Disconnect the B24 or B25 heated oxygen sensor connector.
(b) Remove the engine room junction block from the engine room R/B.
(c) Measure the resistance between the terminals.
Standard resistance (Check for open):
Standard resistance (Check for short):
(d) Reinstall the engine room junction block.
(e) Reconnect the HO2 sensor connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK ECM POWER SOURCE CIRCUIT
7. CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
(a) Disconnect the B24 heated oxygen sensor connector (Bank 1 Sensor 2) or B25 heated oxygen sensor connector (Bank 2 Sensor 2).
(b) Turn the engine switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:
(d) Turn the engine switch off.
(e) Disconnect the B12 ECM connector.
(f) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
Standard resistance (Check for short):
(g) Reconnect the HO2 sensor connector.
(h) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
8. CHECK WHETHER DTC OUTPUT RECURS
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Turn the Techstream on.
(d) Clear the DTCs DTC Check / Clear.
(e) Start the engine.
(f) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(g) Select the following menu items: Powertrain / Engine / Trouble Codes / Pending.
(h) Read the pending DTCs.
Result:
B -- REPLACE ECM Removal
A -- CHECK FOR INTERMITTENT PROBLEMS Symptom Related Diagnostic Procedures