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). Each HO2S is supplied power from the external ignition 1 voltage circuit. The PCM controls each HO2S heater low control circuit with a low side driver. The HO2S heater diagnostic measures the current flow through the low side driver when the engine is running. The PCM will also use the measured current flow, during operation and during engine start-up, to calculate the resistance of the HO2S heater. Based on the resistance, the PCM can predict the temperature of the HO2S heater. If the PCM detects that the HO2S current parameter is out of range for a longer than expected period of time, or if the PCM detects that the calculated HO2S heater resistance is out of range during a cold start, the following DTCs will set:
| • | P0135 for Bank 1 Sensor 1 |
| • | P0141 for Bank 1 Sensor 2 |
| • | P0155 for Bank 2 Sensor 1 |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC P0135 HO2S Heater Performance Bank 1 Sensor 1 |
| • | DTC P0141 HO2S Heater Performance Bank 1 Sensor 2 |
| • | DTC P0155 HO2S Heater Performance Bank 2 Sensor 1 |
Conditions for Running the DTC
Heater Current Test
| • | DTCs P0030, P0036, P0050 are not set. |
| • | The ECT Sensor parameter is more than 60°C (140°F). |
| • | The Engine Speed parameter is between 500-3,000 RPM. |
| • | The Engine Run Time parameter is more than 3 minutes. |
| • | The MAF parameter is between 5-30 g/s. |
| • | DTCs P0135, P0141, and P0155 run 5 tests per key cycle with a 120 second delay between tests once the above conditions are met. |
Heater Resistance Test
| • | DTCs P0030, P0036, P0050 are not set. |
| • | The ignition is OFF for more than 8 hours. |
| • | The ECT Sensor parameter is between -30 to +45°C (-22 to +113°F). |
| • | The difference between the ECT Sensor parameter and the IAT Sensor parameter is less than 8°C (14.4°F). |
| • | The engine is running. |
| • | DTCs P0135, P0141, and P0155 run 5 tests per key cycle with a 120 second delay between tests once the above conditions are met. |
Conditions for Setting the DTC
Heater Current Test
| • | For DTC P0135 or P0155, the PCM detects that the affected HO2S heater current value is less than 0.25 amps or more than 3.12 amps for more than 8 seconds. |
| OR |
| • | For DTC P0141, the PCM detects that the affected HO2S heater current value is less than 0.20 amps or more than 0.91 amps for more than 8 seconds. |
Heater Resistance Test
The PCM detects that the affected HO2S heater calculated resistance is not within an expected range at engine start-up.
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 and Engine Controls Connector End Views | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 | Is DTC P0030, P0036, or P0050 set? | -- | Go to Step 3 | |||||
3 |
Does the affected HO2S Heater parameter move above the specified value? | 0 A | Go to Step 4 | Go to Step 5 | ||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||
5 |
Important: An open OXY SEN fuse may cause DTCs P0135, P0141, and P0155 to set simultaneously. Inspect the OXY SEN fuse for an open. Is the fuse open? | -- | Go to Step 9 | Go to Step 6 | ||||
6 |
Important: Use a known good ground. Do not use the heated oxygen sensor (HO2S) heater low control or the HO2S low signal circuits.
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 16 | ||||
7 |
Does the test lamp blink ON and OFF? | -- | Go to Step 8 | Go to Step 11 | ||||
8 | Measure the resistance of the following circuits with a DMM:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Is the resistance of either circuit more than the specified value? | 5 ohms | Go to Step 17 | Go to Step 14 | ||||
9 | Test each HO2S ignition 1 voltage circuit branch for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 10 | ||||
10 |
Important: Perform the following test on all HO2S. Test the ignition 1 voltage circuit, on the sensor side of the HO2S connector, for a short to ground or a short to the HO2S low signal circuit. Refer to Circuit Testing in Wiring Systems. Is any sensor shorted? | -- | Go to Step 18 | Go to Intermittent Conditions | ||||
11 | Does the test lamp stay ON continuously? | -- | Go to Step 12 | Go to Step 13 | ||||
12 | Test the affected HO2S heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 15 | ||||
13 | Test the affected HO2S 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 20 | Go to Step 15 | ||||
14 | Test for shorted terminals and for poor connections at the harness connector of the affected HO2S. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 | ||||
15 | Test for shorted terminals and for poor connections 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 20 | Go to Step 19 | ||||
16 | Repair the open or high resistance in the affected HO2S heater ignition 1 voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 20 | -- | ||||
17 | Repair the circuit with high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 20 | -- | ||||
18 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the affected HO2S. Refer to one of the following procedures: Did you complete the replacement? | -- | Go to Step 20 | -- | ||||
19 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 20 | -- | ||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||
