DTC P2195 - LNP or LNQ
Diagnostic Instructions
DTC Descriptor
DTC P2195 00: HO2S Signal Biased Lean 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
| 1 000 mV
|
Low Reference
| -
| 400-415 mV
| 1 000 mV
|
Circuit/System 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 utilises the following circuits:
| • | A low reference circuit |
| • | An ignition 1 voltage circuit |
| • | A heater control circuit |
Conditions for Running the DTC
| • | The engine coolant temperature (ECT) is greater than 60°C (140°F). |
| • | The ignition 1 voltage is greater than 10 V. |
| • | The DTC runs continuously once the above conditions are met for 2 s. |
Conditions for Setting the DTC
The ECM detects that the HO2S 1 voltage is less than 350 mV for 11 s.
Action Taken When the DTC Sets
| • | DTC P2195 is a Type B DTC. |
| • | The ECM commands Open Loop fuel control. |
Conditions for Clearing the DTC
DTC P2195 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Engine idling, observe the scan tool HO2S voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the HO2S 1.
- Engine idling, verify the scan tool HO2S parameter is between 350-500 mV.
| ⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
- Verify none of the following conditions exist:
| • | Water intrusion in the HO2S harness connector |
| • | Low fuel system pressure. |
| • | Fuel that is contaminated. |
| • | Exhaust leaks near the HO2S |
| ⇒ | If you find any of the above conditions, repair as necessary. |
- If all circuits test normal, test or replace HO2S 1.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| © Copyright Chevrolet. All rights reserved |
| © Copyright Chevrolet. All rights reserved |
