• | 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. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
HO2S Bank 1 Sensor 1 Signal | P0131 | P0134, P0135 | P0132 | P0133 |
HO2S Bank 1 Sensor 2 Signal | P0137 | P0140 | P0138 | P0140, P2096, P2097 |
HO2S Bank 2 Sensor 1 Signal | P0151 | P0154, P0155 | P0152 | P0153 |
HO2S Bank 2 Sensor 2 Signal | P0157 | P0160 | P0158 | P0160, P2098, P2099 |
Low Reference | -- | P0134, P0135, P0154, P0155 | -- | -- |
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 | |||
Sensor Signal | 0-60 mV | 445-450 mV | 1275 mV |
Low Reference | -- | 445-480 mV | 1275 mV |
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.
Fuel trim bias is used by the ECM to keep the post catalyst HO2S voltage within a range of 580-665 mV. This allows optimal catalyst efficiency under light load conditions, such as at idle or a steady cruise. The ECM constantly monitors how lean or rich the fuel trim bias is commanded, to determine if the fuel trim bias is greater than a calibrated amount.
The HO2S utilizes the following circuits:
• | A signal circuit |
• | A low reference circuit |
• | An ignition voltage circuit |
• | A heater control circuit |
• | Before the ECM can report DTC P2097 or P2099 failed, DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P2177, P2178, P2179, 2180, P2187, P2188, P2189, P2190, P2231, P2232, P2234, P2235, P2270, P2271, P2272, and P2273 must run and pass. |
• | DTCs P0100, P0101, P0102, P0103, P0420, P0430, P0442, P0443, P0455, P0458, and P0459 are not set. |
• | The engine speed is 1200-2920 RPM. |
• | The engine load is 17-20 percent and steady. |
• | The closed loop fuel control is active for greater than 3 seconds. |
• | The front and rear HO2S are in Closed Loop. |
• | The calculated exhaust gas temperature is greater than 300°C (572°F). |
• | DTCs P2097 and P2099 run continuously when the conditions above have been met for greater than 200 seconds. |
The post catalyst fuel trim correction factor is biased rich by more than -8 percent of the HO2S signal value for more than 4 seconds or for a cumulative of 50 seconds.
DTCs P2097 and P2099 are Type B DTCs.
DTCs P2097 and P2099 are Type B DTCs.
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
⇒ | If any of the above DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle . |
Caution: Refer to Road Test Caution in the Preface section.
Important: The rear heated oxygen sensor (HO2S) must be in closed loop for this diagnostic to run. A road load condition is necessary to obtain closed loop.
• | Rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 . |
• | Water intrusion in the HO2S harness connector |
• | High fuel system pressure--Refer to Fuel System Diagnosis . |
• | Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
• | Fuel saturation of the evaporative emissions (EVAP) canister |
• | Restricted exhaust |
• | Contaminated HO2S - Silicon |
⇒ | If you find any of the above conditions, repair as necessary. |
⇒ | If greater than the specified range, test the signal circuit of the HO2S sensor for a short to voltage. If the circuit/connections test normal, replace the ECM. |
⇒ | If greater than the specified value, replace the HO2S 2. |
⇒ | If a parameter changes abruptly, repair the harness/connections as necessary. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for engine control module replacement, setup, and programming |