P1166
DTC P1137 or P1166
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Strategy Based Diagnosis Strategy Based Diagnosis
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions
DTC Descriptors
DTC P1137
- HO2S Circuit Low Voltage During Power Enrichment Sensor 1
DTC P1166
- HO2S Circuit Low Voltage During Power Enrichment Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
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 DTC
* The engine airflow is greater than 6 g/s.
* The startup engine coolant temperature is greater than 60°C (140°F).
* The ignition 1 voltage is greater than 10 volts.
* The engine has been operating for 10 seconds.
* The engine is in power enrichment (PE) mode.
* The DTCs run continuously when the above conditions are met for 2 seconds.
Conditions for Setting the DTC
The engine control module (ECM) detects that the HO2S voltage is less than 350 mV and the air/fuel ratio is less than 13.5:1 during PE mode.
Action Taken when the DTC Sets
DTCs P1137 and P1166 are type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P1137 and P1166 are type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (w/Throttle Actuator Controls) Electrical DiagramsEngine Controls Schematics (w/o Throttle Actuator Control) Electrical Diagrams
Connector End View Reference
* Engine Control Module Connector End Views (w/ Throttle Actuator Control) Engine Control Module Connector End Views (w/ Throttle Actuator Control)Engine Control Module Connector End Views (w/o Throttle Actuator Control) Engine Control Module Connector End Views (w/o Throttle Actuator Control)
* Engine Controls Connector End Views (w/ Throttle Actuator Control) Engine Controls Connector End Views (w/ Throttle Actuator Control)Engine Controls Connector End Views (w/o Throttle Actuator Control) Engine Controls Connector End Views (w/o Throttle Actuator Control)
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
* Scan Tool Data List (w/ Throttle Actuator Control) Scan Tool Data List (w/ Throttle Actuator Control)Scan Tool Data List (w/o Throttle Actuator Control) Scan Tool Data List (w/o Throttle Actuator Control)
* Scan Tool Data Definitions (w/ Throttle Actuator Control) Scan Tool Data Definitions (w/ Throttle Actuator Control)Scan Tool Data Definitions (w/o Throttle Actuator Control) Scan Tool Data Definitions (w/o Throttle Actuator Control)
* Scan Tool Output Controls (w/ Throttle Actuator Control) Scan Tool Output Controls (w/ Throttle Actuator Control)Scan Tool Output Controls (w/o Throttle Actuator Control) Scan Tool Output Controls (w/o Throttle Actuator Control)
Circuit/System Verification
1. With the engine running, observe the heated oxygen sensor (HO2S) voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
2. 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
1. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
2. Ignition ON, verify that the HO2S parameter is between 350-500 mV.
• If less than 350 mV, test the signal circuit of the HO2S sensor for a short to ground. If the circuit/connections test normal, replace the ECM.
3. Verify that none of the following conditions exist:
* Engine vacuum leaks
* Exhaust leaks near the HO2S
* Water intrusion in the HO2S harness connector
* Low fuel system pressure-Refer to Fuel System Diagnosis Fuel System Diagnosis.
* Lean fuel injectors-Refer to Fuel Injector Balance Test with Special Tool Fuel Injector Balance Test with Special Tool.
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis Alcohol/Contaminants-in-Fuel Diagnosis.
* Contaminated HO2S-Silicon
• If you find any of the above conditions, repair as necessary.
4. If all circuits/connections test normal, replace the applicable HO2S.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Heated Oxygen Sensor 1 Replacement Heated Oxygen Sensor 1 Replacement
* Heated Oxygen Sensor 2 Replacement Heated Oxygen Sensor 2 Replacement
* Control Module References Control Module References for engine control module replacement, setup, and programming