Diagnostic Instructions
DTC Descriptors
DTC P2195: HO2S Circuit Low Voltage During Power Enrichment Sensor 1
Typical Scan Tool Data
HO2S 1
Circuit
| Short to Ground
| Open
| Short to Voltage
|
Operating Conditions:
Engine operating in Closed Loop
Parameter Normal Range:
Fluctuates above and below 350-500 mV
|
HO2S 1 Signal
| 0 mV
| 400-415 mV
| 1000 mV
|
Low Reference
| --
| 400-415 mV
| 1000 mV
|
Circuit Description
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. The 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 low reference circuit |
| • | An ignition 1 voltage circuit |
| • | A heater control circuit |
Conditions for Running the DTC
| • | DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0443, P0488, P0502, P0506, and P0507 are not set. |
| • | The air fuel ratio is less than or equal to 13.5:1. |
| • | The engine coolant temperature (ECT) is more than 60°C (140°F). |
| • | The ignition 1 voltage is greater than 10 volts. |
| • | The engine is in power enrichment (PE) mode. |
| • | The DTC runs continuously once the above conditions are met for 2 seconds. |
Conditions for Setting the DTC
The ECM detects that the HO2S 1 voltage is less than 350 mV for 11 seconds during PE mode.
Action Taken when the DTC Sets
| • | DTC P2195 is a Type B DTC. |
| • | The ECM commands Open Loop fuel control. |
Conditions for Clearing the MIL/DTC
DTC P2195 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics
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 HO2S voltage parameter. The reading should fluctuate above and below the range of 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 List.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector of the HO2S 1.
- Engine idling, verify that the HO2S parameter is between 350-500 mV.
| ⇒ | If less than 350 mV, test the signal circuit for a short to ground. If the circuit/connections test normal, replace the ECM. |
- Verify that none of the following conditions exist:
| • | Water intrusion in the HO2S harness connector |
| • | Exhaust leaks near the HO2S |
| • | Contaminated HO2S--Silicon |
| ⇒ | If you find any of the above conditions, repair as necessary. |
- If all circuits/connections test normal, replace HO2S 1.
Repair Instructions
Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
