Circuit Description
Heating elements inside the heated oxygen sensors (HO2S) minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal, the HO2S heater operation is controlled by the powertrain control module (PCM). A high side driver supplies ignition power to the bank 1 HO2S 1, and is equipped with a current monitor. Two low side drivers provide the heater ground path. The bank 2 HO2S 1 is supplied power from the external ignition 1 voltage circuit, and uses the same low side drivers. When the ignition switch is turned ON the PCM performs an HO2S heater circuit check using the high side driver current monitor circuit. When the engine is started, all three drivers are switched ON. One of the low drivers is for heater warm-up only, and is used until the proper heater temperature is reached. When the warm-up low driver is switched OFF, the heater ground path is controlled through the remaining low side driver. The PCM now records the total heater circuit current, if the heater current remains stable the PCM momentarily turns OFF the high side driver. The PCM now records the bank 2 HO2S 1 current. This value is subtracted from the previously recorded total and is used to determine the condition of the heater circuit. If the PCM detects a HO2S bank 2 sensor 1 heater current outside of the calibrated range, DTC P0155 will set.
Conditions for Running the DTC
| • | DTCs P0030, P1031, P1032 are not set. |
| • | The Engine Speed parameter is between 500-3,000 RPM. |
| • | The Engine Run Time is more than 3 minutes. |
| • | The MAF Sensor parameter is between 4-30 g/s. |
| • | All of the above conditions are met for 2 seconds. |
Conditions for Setting the DTC
The PCM detects an HO2S bank 2 sensor 1 heater current value outside the calibrated range.
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 | Value(s) | 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 |
Did DTCs P0030, P1031, and P1032 fail this ignition? | -- | Go to Step 3 | |
3 |
Did DTCs P0135 and P0155 fail this ignition? | -- | Go to Step 4 | |
4 | Is DTC P0155 set? | -- | Go to Step 5 | Go to Intermittent Conditions |
5 |
Important: Use a known good ground. Do not use the heated oxygen sensor (HO2S) heater low control circuit or the HO2S low signal circuit.
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 7 |
6 |
Is the voltage within the specified range? | 4-6 V | Go to Step 9 | Go to Step 8 |
7 | Test the HO2S bank 2 sensor heater ignition 1 voltage circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | -- |
8 | Test the HO2S bank 2 sensor 1 heater low control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 |
9 | Test for an intermittent and for a poor connection at the harness connector of the HO2S bank 2 sensor 1. 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 13 | Go to Step 11 |
10 | Test for an intermittent and for a poor connection at the harness connector of the powertrain control module (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 13 | Go to Step 12 |
11 | Replace HO2S bank 2 sensor 1. Refer to Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 13 | -- |
12 | Replace the PCM. Refer Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 |
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
