Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provide an overview of each diagnostic category. |
DTC Descriptors
DTC P0136: HO2S Circuit Bank 1 Sensor 2DTC P0156: HO2S Circuit Bank 2 Sensor 2
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
HO2S Bank 1 Sensor 1 Signal | P0131 | P0130 | P0132 | P0130, P0133, P0134 |
HO2S Bank 1 Sensor 2 Signal | P0137 | P0136 | P0138 | P0136, P0139, P0140 |
HO2S Bank 2 Sensor 1 Signal | P0151 | P0150 | P0152 | P0150, P0153, P0154 |
HO2S Bank 2 Sensor 2 Signal | P0157 | P0156 | P0158 | P0156, P0159, P0160 |
Low Reference | -- | P0130, P0136, P0150, P0156 | P0132, P0138, P0152, P0158 | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: Fluctuates within 700-900 mV. | |||
Sensor Signal | 0-60 mV | 400-430 mV | 5000 mV |
Low Reference | -- | 400-430 mV | 5000 mV |
Circuit Description
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
The HO2S utilizes the following circuits:
| • | A signal circuit |
| • | A low reference circuit |
| • | An ignition 1 voltage circuit |
| • | A heater control circuit |
Conditions for Running the DTCs
| • | DTCs P0102, P0103, P0107, P0108, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0150, P0151, P0152, P0153, P0154, P0221, P0222, P0223, P0230, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0335, P0336, P0337 P0340, P0341, P0443, P0458, and P0459 are not set. |
| • | The ignition is ON. |
| • | The engine coolant temperature (ECT) sensor is greater than 75°C (167°F). |
| • | The DTCs run continuously once the above conditions are met. |
OR
| • | DTCs P0137, P0138, P0139, P0140, P0157, P0158, P0159, and P0160 are not set. |
| • | The ignition is ON. |
| • | The HO2S voltage is between 361-488 mV. |
| • | The exhaust gas temperature at the HO2S is greater than 350°C (662°F). |
| • | The DTCs run continuously once the above conditions are met. |
Conditions for Setting the DTCs
The engine control module (ECM) detects the HO2S resistance is greater than 60K Ohms for 10 seconds.
Action Taken when the DTCs Set
DTCs P0136 and P0156 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0136 and P0156 are Type B DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- Engine idling, observe the scan tool HO2S voltage parameter. The reading should fluctuate above and below 350-550 mV.
- If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate HO2S sensor.
- Ignition ON, test for less than 0.1 volt between the low reference circuit and ground.
- Verify the scan tool HO2S parameter is between 350-500 mV.
- Install a 3-A fused jumper wire between the signal circuit and the low reference circuit. Verify the scan tool HO2S sensor parameter is less than 60 mV.
- If all circuits test normal, test or replace the HO2S sensor.
| ⇒ | If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for engine control module replacement, setup, and programming |
