Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature and to provide an accurate voltage signal. The PCM controls the HO2S 2 heater low control circuit with a low side driver. The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms once per second. If the PCM detects that the HO2S 2 heater resistance is not within an expected range, DTC P0054 will set for bank 1 sensor 2.
The HO2S 2 has the following circuits:
| • | The HO2S 2 high signal circuit |
| • | The HO2S 2 low signal circuit |
| • | The HO2S 2 ignition 1 voltage circuit |
| • | The HO2S 2 heater low control circuit |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0054 HO2S Heater Resistance Bank 1 Sensor 2
Conditions for Running the DTC
| • | The ignition is OFF for more than 10 hours. |
| • | The ECT Sensor parameter minus the IAT Sensor parameter is less than 8°C (14°F) at engine start-up. |
| • | The ECT Sensor parameter is between -30 and +45°C (-22 and +133°F) at engine start-up. |
| • | The system voltage is between 9-18 volts. |
| • | This diagnostic runs once per valid cold start once the above conditions are met. |
Conditions for Setting the DTC
The PCM detects that the HO2S 2 heater calculated resistance is not within an expected range at engine start-up for 1 second.
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. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Important: The HO2S 2 Heater parameter may toggle to 0.00 A momentarily.
Is the amperage within the specified range? | 0.21-0.95 A | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections |
4 | Test the fuse that powers the heated oxygen sensor (HO2S) 2 for an open. Refer to Circuit Testing . Is the fuse open? | -- | Go to Step 8 | Go to Step 5 |
5 |
Important: Use a known good ground. DO NOT use the HO2S 1 or HO2S 2 heater low control circuits, or the HO2S 1 or HO2S 2 low signal circuits.
Is the difference between the system voltage and either measured voltage more than the specified voltage? | 0.5 V | Go to Step 12 | Go to Step 6 |
6 |
Is either measured voltage more than the specified value? | 0.5 V | Go to Step 7 | Go to Step 10 |
7 | Test the HO2S 1 and the HO2S 2 heater low control circuits for an open or high resistance condition. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
8 | Test the HO2S 1 and the HO2S 2 ignition 1 voltage circuits for a short to ground and replace the fuse. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 |
9 |
Important: Perform the following test on all HO2S' that are supplied voltage by the suspect circuit. Test the HO2S 1 and the HO2S 2 ignition 1 voltage circuits on the sensor side of the HO2S connectors for a short to ground. Refer to Circuit Testing . Is any sensor shorted to ground? | -- | Go to Step 13 | Go to Testing for Intermittent Conditions and Poor Connections |
10 | Test for an intermittent and for a poor connection at the HO2S 1 and the HO2S 2. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
11 | Test for shorted terminals and poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
12 | Repair the open or high resistance condition in the HO2S 1 or the HO2S 2 ignition 1 voltage circuit. Refer to Wiring Repairs and Heated Oxygen Sensor Wiring Repairs . Did you complete the repair? | -- | Go to Step 15 | -- |
13 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 1 or the HO2S 2. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 15 | -- |
15 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 16 |
16 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
