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 provides an overview of each diagnostic category. |
DTC Descriptors
DTC P2195: Heated Oxygen Sensor (HO2S) Signal Biased Lean Sensor 1DTC P2196: Heated Oxygen Sensor (HO2S) Signal Biased Rich Sensor 1
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
HO2S 1 Input | P2195, P2237, P2238 | P2237, P2238 | P2196, P2237, P2239 | P2237, P2238, P2A00 |
Low Reference | P2196, P2237, P2239, P2252 | P2237, P2238 | P2196, P2237, P2238, P2253 | P2237, P2238 |
Component | Cause | DTCs | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Heated Oxygen Sensor 1 |
| P0171, P2195, P2A00 | ||||||||
| P0172, P2196, P2A00 |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop Parameter Normal Range: Fluctuates between 3.2-3.4 volts | |||
HO2S 1 Input | 4.99 volts* | 3.3-3.4 volts | 0.00 volts* |
Low Reference | 4.99 volts* | 3.3-3.4 volts | 0.00 volts* |
*Actual circuit voltage is not the same as scan tool displayed voltage | |||
Circuit Description
The heated oxygen sensor (HO2S) 1 is a wide band or wide range design. As with all oxygen sensors, the wide band HO2S measures the amount of oxygen in the exhaust system, but provides more information than the typical switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The powertrain control module (PCM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the PCM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The PCM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the PCM can determine the concentration of oxygen in the exhaust. The HO2S input signal is displayed as a voltage within the range of 1-5 volts, with a steady value of 3.2-3.3 volts equal to the air fuel ratio of 14.7:1. If the HO2S 1 input voltage is lower than the specified reference voltage, the PCM determines that the air/fuel ratio is richer than the theoretical air/fuel ratio and reduces the fuel. If the input voltage from the HO2S 1 is higher than the specified reference voltage, the PCM determines that the air/fuel ratio is leaner and increases the fuel. By repeating these operations, the PCM can adjust the air/fuel ratio in order to be closer to the theoretical air/fuel ratio. Control of the fuel delivery system as just described is known as Closed Loop operation.
The HO2S utilizes the following circuits:
| • | A signal circuit |
| • | A low reference circuit |
| • | An ignition 1 voltage circuit |
| • | A heater control circuit |
Air Fuel Mixture | Exhaust O2 Content | HO2S 1 Output | Fuel System Response |
|---|---|---|---|
Lean Mixture | High Oxygen | More Than 3.4 V | Rich Command |
Rich Mixture | Low Oxygen | Less Than 3.2 V | Lean Command |
Conditions for Running the DTC
| • | DTCs P0031, P0032, P0051, P0052, P0100, P0101, P0102, P0103, P0110, P0112, P0113, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0171, P0172, P0220, P0222, P0223, P0300-P0304, P0335, P0340, P0341, P0385, P0441, P0455, P0456, P0500, P2135, P2238, P2239, P2252, P2253 are not set. |
| • | The engine has been running for greater than 30 seconds. |
| • | The engine is operating in Closed Loop. |
| • | The DTCs run continuously when the above conditions have been met. |
Conditions for Setting the DTC
P2195
The HO2S 1 input voltage is greater than 3.8 volts for greater than 2 seconds.
P2196
The HO2S 1 input voltage is less than 2.8 volts for greater than 2 seconds.
Action Taken when the DTC Sets
DTCs P2195 and P2196 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P2195 and P2196 are Type B DTCs.
Diagnostic Aids
| • | Test for a contaminated oxygen sensor. Silicone and other contaminants can cause the oxygen sensor to provide false exhaust oxygen content readings. If contamination is found, determine the cause and correct the condition before replacing the HO2S. |
| • | The scan tool output control feature, Fuel Injector Modification, can be used at idle to check the oxygen sensor performance. Commanding the Fuel Injector Modification Commanded State to 25 percent should cause the HO2S 1 voltage to decrease to less than 3 volts. Changing the Fuel Injector Modification Commanded State to -12 percent should cause the HO2S 1 voltage to increase to greater than 3.35 volts. An oxygen sensor that fails to respond accordingly may be faulty or contaminated. When performing the Fuel Injector Modification with the scan tool, the Loop Status will remain Open Loop and the Short Term FT will be fixed at 0 percent. |
| • | Test the HO2S 1 for water intrusion into the wiring harness and the sensor housing. Water can create a short to voltage in the HO2S signal circuit causing a false lean indication. |
Reference Information
Schematic Reference
Connector End View Reference
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
- Ignition ON, observe the DTC information with a scan tool. Verify DTCs P2237, P2238, P2239, P2252, P2253 are not set.
- Engine running at normal operating temperature, observe the scan tool HO2S 1 voltage parameter. The reading should fluctuate between 3.2-3.4 volts.
- 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.
| ⇒ | If DTC P2237, P2238, P2239, P2252, P2253 is set, diagnose the DTC first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector of the HO2S 1.
- Ignition ON, test for 3.4-3.6 volts between the HO2S 1 input circuit terminal 3 and ground.
- Test for the following conditions:
- If all conditions test normal, replace the HO2S 1.
| ⇒ | If greater than the specified range, test the HO2S 1 input circuit for a short to voltage. If the circuit tests normal, replace the PCM. |
| ⇒ | If less than the specified range, test the HO2S 1 input circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the PCM. |
| • | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis. |
| • | Splits, kinks, or improper connections at the vacuum hoses |
| • | The fuel system operating pressure is incorrect--Refer to Fuel System Diagnosis. |
| • | The fuel injectors are operating lean or rich--Refer to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F). |
| • | Vacuum leaks at the intake manifold, manifold fittings, or throttle body |
| • | Faulty crankcase ventilation system--Refer to Crankcase Ventilation System Inspection/Diagnosis. |
| • | A collapsed or restricted air intake duct and a restricted or dirty air filter |
| • | The incorrect operation of the evaporative emission control system--Refer to Evaporative Emission Control System Diagnosis. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for control module replacement, setup, and programming |
