For 1990-2009 cars only
DTC Descriptor
DTC P2A01: HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 2Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
HO2S High Signal | P0137, P0140, P2A01 | P0137, P0140, P2A01 | P0137, P0140, P2A01 | P0138, P0140, P2A01 | P0140, P2A01 |
HO2S Low Signal | P2A01 | P0137, P0138, P0140, P2A01 | P0137, P0138, P0140, P2A01 | P0138, P0140, P2A01 | P2A01 |
Typical Scan Tool Data
HO2S Sensor Voltage Circuits | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
HO2S High Signal | 50-850 mV | 0-45 mV | Approximately 450 mV | Approximately 1106 mV |
HO2S Low Signal | 50-850 mV | 50-850 mV | 400-600 mV | 50-850 mV |
Circuit/System Description
The heated oxygen sensor (HO2S) 2 is used for catalyst monitoring. This diagnostic runs once per ignition cycle. This diagnostic consists of 2 tests, a passive test and an intrusive test. During the passive test, if the HO2S 2 voltage transitions below 290 mV and above 685 mV, the DTC will pass for this ignition cycle. If the DTC does not pass during the passive test, the intrusive test will begin. During the intrusive test, the control module will force the air-to-fuel ratio rich and/or lean. The control module then waits for a predicted response from the HO2S. If the HO2S 2 voltage transitions below 290 mV and above 685 mV, the DTC will pass for this ignition cycle.
Conditions for Running the DTC
Passive Test
| • | DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P1133, P2119, P2135 are not set. |
| • | The engine is running for at least 6 seconds. |
| • | The ignition voltage is between 10-18 volts. |
Intrusive Test
| • | DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0461, P0464, P0496, P1133, P2119, P2135 are not set. |
| • | The Engine Run Time parameter is more than 6.5 minutes. |
| • | The ignition voltage is between 10-18 volts. |
| • | The Engine Speed parameter is between 2,500-3,000 RPM. |
| • | The MAF Sensor parameter is between 12-45 g/s. |
| • | The Vehicle Speed parameter is between 33-130 km/h (21-81 mph). |
| • | When all of the above conditions have been met for at least 2.5 seconds, the following conditions must also be met: |
| - | The evaporative emission (EVAP) purge diagnostic is not active. |
| - | The Short Term FT Bank 1 or the Short Term FT Bank 2 parameter is between +5 and -5 percent. |
| - | The Loop Status parameter is closed. |
| - | The EVAP purge solenoid is greater than 0 percent. |
Conditions for Setting the DTC
| • | The HO2S 2 parameter is between 250-775 mV during the passive test. |
| • | One of the following tests fail: |
Lean Intrusive Test
| - | The control module detects that the HO2S 2 voltage is more than 250 mV for 10 seconds. |
| - | The control module detects that the HO2S 1 voltage is less than 100 mV. |
Rich Intrusive Test
| - | The control module detects that the HO2S 2 voltage is less than 775 mV for 8 seconds. |
| - | The control module detects that the HO2S 1 voltage is more than 825 mV. |
| • | This diagnostic runs once per trip. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
| • | Allow the engine to reach operating temperature. With the engine running, observe the affected HO2S parameter with a scan tool. |
| ⇒ | The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fueling changes. |
| ⇒ | The HO2S 2 value should change more than 200 mV when the throttle is quickly cycled 3 times from Closed to Wide Open and back to Closed after running the engine at 1500 RPM for 30 seconds. |
| • | If any HO2S heater DTCs are set, diagnose those DTCs first. |
| • | The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination: |
Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
| - | A silicon contaminated HO2S |
| - | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis . |
| - | Engine oil consumption--Refer to Oil Consumption Diagnosis . |
| - | Engine coolant consumption--Refer to Loss of Coolant . |
Circuit/System Testing
- Ignition OFF, disconnect the affected HO2S.
- Ignition ON, verify the applicable scan tool HO2S parameter is approximately 450 mV.
- Install a 3A fused jumper wire at the high signal circuit terminal. Toggle the jumper wire between the HO2S low signal circuit terminal and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV, and more than 1,000 mV.
- If all circuits test normal, replace the appropriate HO2S.
| ⇒ | If more than the specified value, test the HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than the specified value, test the HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM. |
| ⇒ | If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal and low signal circuits for an open/high resistance. If the circuit tests normal, replace the ECM. |
Repair Instructions
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.
Repair Verification
- Clear the DTCs with a scan tool
- Turn OFF the ignition for 30 seconds.
- Start the engine.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
| ⇒ | If this DTC resets, repeat this procedure. |
| ⇒ | If this DTC does not reset but others do, perform those diagnostics. |
