Circuit Description
The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The PCM controls the heater by grounding the control circuit with a solid state device called a driver. If the PCM detects the control circuit voltage is not within a predetermined range when the circuit is commanded ON or OFF, this DTC sets.
DTC Descriptors
This diagnostic procedure supports the following DTCs.
| • | DTC P0030 Heater Control Circuit Bank 1 Sensor 1 |
| • | DTC P0036 Heater Control Circuit Bank 1 Sensor 2 |
| • | DTC P0050 Heater Control Circuit Bank 2 Sensor 1 |
| • | DTC P0056 Heater Control Circuit Bank 2 Sensor 2 |
Conditions for Running the DTC
| • | Conditions for running DTCs P0030 and P0050 |
| - | The engine is operating. |
| - | DTCs P0133, P0153, P2238, P2241, P2242, P2243, P2245, P2247, P2249, P2252, P2255, P2256, P2297, P2298, P2414, P2415, P2627, P2628, P2630, and P2631 are not set. |
| - | The heater control circuit is being commanded ON and OFF. |
| • | Conditions for running DTCs P0036 and P0056 |
| - | The ignition is ON. |
| - | The heater control circuit is being commanded ON and OFF. |
| • | DTCs P0030, P0036, P0050, and P0056 run continuously once the above conditions are met for more than 1 second. |
Conditions for Setting the DTC
| • | The PCM detects the heater control circuit voltage is less than a predetermined range when the circuit is commanded OFF. |
| • | The PCM detects the heater control circuit voltage is more than a predetermined range when the circuit is commanded ON. |
| • | The condition exists for more than 1 second. |
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame/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. |
Diagnostic Aids
| • | An open fuse in the HO2S heater circuit may be caused by the heater element in one of the sensors. The condition may not be present until the sensor operates for a period of time. If no fault is present in the heater circuit, monitor the amperage of each heater using the DMM to determine if one of the heater elements is the cause of the open fuse. |
| • | Inspect the sensor pigtail or the harness for contacting the exhaust system. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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-Engine Controls? | -- | Go to Step 2 | |
2 |
Does DTC P0030, DTC P0036, DTC P0050, or DTC P0056 set? | -- | Go to Step 4 | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids |
Are DTCs P0030, P0036, P0050, and P0056 set at the same time? | -- | Go to Step 12 | Go to Step 5 | |
5 |
Important: The ignition must be OFF when disconnecting or connecting the HO2S electrical connector. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 12 |
6 | Connect a test lamp between the ignition voltage circuit of the HO2S and the heater control circuit. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 7 |
7 |
Does the test lamp flash ON and OFF? | -- | Go to Step 10 | Go to Step 9 |
8 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
9 |
Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
10 | Test for an intermittent and for a poor connection at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
11 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14 |
12 |
Important: The ignition voltage circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition voltage circuit. Did you complete the repair? | -- | Go to Step 15 | -- |
13 | Replace the HO2S. Refer to the appropriate procedure: Did you complete the replacement? | -- | Go to Step 15 | -- |
14 |
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 | |
