• | 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, P2096, P2097 |
HO2S Bank 1 Sensor 2 Signal | P0137 | P0140 | P0138 | P0140 |
HO2S Bank 2 Sensor 1 Signal | P0151 | P0154, P0155 | P0152 | P0153, P2098, P2099 |
HO2S Bank 2 Sensor 2 Signal | P0157 | P0160 | P0158 | P0160 |
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.
• | DTC P0201, P0202, P0203, P0204, P0205, P0206 P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, or P0277 is not set. |
• | The ignition voltage is greater than 10 volts. |
• | The engine speed is greater than 25 RPM. |
• | The HO2S 1 heater command is greater then 70 percent for greater than 8 seconds. |
• | The amount of air flow into the engine is greater than 220 grams for grater than 5 seconds. |
• | The Closed Loop fuel control is enabled. |
• | The ECM is not commanding the air/fuel mixture lean. |
• | DTC P0131 and P0151 run continuously once the conditions above exist for greater than 100 mS. |
• | DTC P0116, P0117, P0118, P0119, P0201, P0202, P0203, P0204, P0205, P0206 P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, or P0277 is not set. |
• | The ignition voltage is greater than 10 volts. |
• | The engine speed is greater than 25 RPM. |
• | The HO2S 1 heater command is greater then 70 percent for greater than 8 seconds. |
• | The conditions for a cold start are present. |
• | The engine coolant temperature (ECT) during the previous ignition cycle was greater than 60°C (140°F). |
• | The ECT at startup is less than 40°C (104°F). |
• | DTC P0131 and P0151 run continuously once the conditions above exist for greater than 100 mS. |
The ECM detects that an HO2S 1 signal voltage is less than 60 mV while the corresponding HO2S 2 voltage is greater than 500 mV.
The ECM detects that an HO2S 1 signal voltage is less than 60 mV after a cold start with the engine coolant temperature (ECT) less than 40°C (104°F).
DTCs P0131 and P0151 are Type B DTCs.
DTCs P0131 and P0151 are Type B DTCs.
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Control Module References for scan tool information
⇒ | If less than the specified range, test the signal circuit terminal B for a short to ground. If the circuit/connections test normal, replace the ECM. |
⇒ | If greater than the specified range, test the signal circuit terminal B for a short to voltage. If the circuit/connections test normal, replace the ECM. |
⇒ | If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM. |
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance or for a short to voltage. If the circuit/connections test normal, replace the ECM. |
• | Lean fuel injectors--Refer to Fuel Injector Solenoid Coil Test. |
• | Low fuel system pressure--Refer to Fuel System Diagnosis. |
• | Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis. |
• | Exhaust leaks near the HO2S |
• | Engine vacuum leaks |
⇒ | If you find any of the above conditions, repair as necessary. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for engine control module replacement, setup, and programming |