DTC Descriptors
DTC P0137: HO2S Circuit Low Voltage Bank 1 Sensor 2DTC P0138: HO2S Circuit High Voltage Bank 1 Sensor 2
DTC P0140: HO2S Circuit Insufficient Activity Bank 1 Sensor 2
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
HO2S High Signal | P0137, P0140, P2A01 | P0137, P0140, P2A01 | P0137, P0140, P2A01 | P0138, P0140, P2A01 | P0140, P2A01 |
HO2S Low Signal | P2A01 | P0137, P0138, P0140, P2A01 | P0137, P0138, P0140, P2A01 | P0138, P0140, P2A01 | P2A01 |
Typical Scan Tool Data
HO2S Sensor Voltage Circuits | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
HO2S High Signal | 50-850 mV | 0-45 mV | Approximately 450 mV | Approximately 1106 mV |
HO2S Low Signal | 50-850 mV | 50-850 mV | 400-600 mV | 50-850 mV |
Circuit/System Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The control module supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the control module operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.
Conditions for Running the DTC
DTC P0137
| • | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P2119, P2135 are not set. |
| • | DTCs P0420 and P2A01 are not commanding fuel. |
| • | The system voltage is between 9-18 volts. |
| • | The scan tool special functions are not active. |
| • | The TP Indicated Angle parameter is between 4-40 percent. |
| • | The ECT Sensor parameter is less than 131°C (268°F). |
| • | The Air Fuel Ratio parameter is between 0.9-1.1. |
| • | The Loop Status parameter is closed. |
| • | All fuel injectors are ON. |
| • | The traction control is not active. |
| • | The above conditions have been met for at least 3 seconds. |
DTC P0138
| • | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P2119, P2135 are not set. |
| • | DTCs P0420 and P2A01 are not commanding fuel. |
| • | The system voltage is between 10-18 volts. |
| • | The scan tool special functions are not active. |
| • | The following conditions must be met for at least 3 seconds: |
| - | The TP Indicated Angle parameter is between 3-40 percent. |
| - | The Air Fuel Ratio parameter is between 0.9-1.1. |
| - | The Loop Status parameter is closed. |
DTC P0140 - Regular Test
| • | DTCs P0036, P0054, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P2119, P2135 are not set. |
| • | DTCs P0420 and P2A01 are not commanding fuel. |
| • | The system voltage is between 10-18 volts. |
| • | The scan tool special functions are not active. |
| • | The Engine Run Time parameter is more than 2 minutes. |
| • | The TP Indicated Angle parameter has changed more than 8 percent at least 3 times. |
| • | The Loop Status parameter is closed. |
| • | The predicted HO2S temperature is more than 0°C (32°F). |
DTC P0140 - Fast Pass Test
| • | DTCs P0036, P0054, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P2119, P2135 are not set. |
| • | DTCs P0420 and P2A01 are not commanding fuel. |
| • | The system voltage is between 10-18 volts. |
| • | The scan tool special functions are not active. |
| • | This vehicle uses the following 2 methods to enable and run this diagnostic: |
| - | The Engine Run Time parameter is less than 90 seconds. |
| - | OR |
| - | A cold start condition has been detected, identified by the following conditions: |
| • | The Start-Up ECT parameter is less than 35°C (95°F). |
| • | The Start-Up intake air temperature (IAT) parameter is less than 35°C (95°F). |
| • | The difference between the Start-Up ECT parameter and the Start-Up IAT parameter is less than 6°C (10.8°F). |
Conditions for Setting the DTC
DTC P0137
| • | The control module detects that the HO2S 2 signal voltage remains below 75 mV for more than 2 minutes. |
| • | This diagnostic runs continuously. |
DTC P0138
| • | The HO2S 2 voltage is more than 925 mV for longer than 120 seconds. |
| • | This diagnostic runs continuously. |
DTC P0140 - Fast Pass Test
During the fast pass, the HO2S 2 voltage is between 350-550 mV for longer than 18 seconds within the first 90 seconds of engine run time. If the fast pass test does not report a pass, then the regular test is initiated.
DTC P0140 - Regular Test
| • | During the regular test, the HO2S 2 voltage is between 380-525 mV for at least 2 minutes. |
| • | This diagnostic runs once per trip. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
| • | Allow the engine to reach operating temperature. With the engine running, observe the affected HO2S parameter with a scan tool. |
| ⇒ | The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes. |
| ⇒ | The HO2S 2 value should change more than 200 mV when the throttle is quickly cycled 3 times from Closed to Wide Open and back to Closed after running the engine at 1500 RPM for 30 seconds. |
| • | If any HO2S heater DTCs are set, diagnose those DTCs first. |
| • | The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination: |
Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
| - | A silicon contaminated HO2S |
| - | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
| - | Engine oil consumption--Refer to Oil Consumption Diagnosis . |
| - | Engine coolant consumption--Refer to Loss of Coolant . |
Circuit/System Testing
- Ignition OFF, disconnect the affected HO2S.
- Ignition ON, verify the applicable scan tool HO2S parameter is approximately 450 mV.
- Install a 3A fused jumper wire at the high signal circuit terminal. Toggle the jumper wire between the HO2S low signal circuit terminal and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV, and more than 1,000 mV.
- If all circuits test normal, replace the appropriate HO2S.
| ⇒ | If more than the specified value, test the HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than the specified value, test the HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal and low signal circuits for an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Repair Verification
- Clear the DTCs with a scan tool
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
| ⇒ | If this DTC resets, repeat this procedure. |
| ⇒ | If this DTC does not reset but others do, perform those diagnostics. |
