Circuit Description
Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. A low side driver within the engine control module (ECM) is pulse-width controlled to provide current to the heater elements. During warm-up, the ECM will reduce the ON time to prevent thermal shock to the sensor components from moisture in the exhaust system. The ECM will not allow full HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The ECM periodically monitors the HO2S operating state by briefly turning OFF the heater low side driver at regular intervals. A small reference voltage of approximately 3.6 volts is present at the heater low control circuit. When the low side driver is commanded ON, the reference voltage is low. When the low side driver is commanded OFF, the reference voltage is high, close to battery voltage. The ECM calculates the HO2S element resistance based on the HO2S heater command voltage and calculated exhaust gas temperature. If the ECM detects that the HO2S heater element resistance is too high, the following DTCs will set:
| • | DTC P0135 for HO2S bank 1 sensor 1 |
| • | DTC P0141 for HO2S bank 1 sensor 2 |
| • | DTC P0155 for HO2S bank 2 sensor 1 |
| • | DTC P0161 for HO2S bank 2 sensor 2 |
Conditions for Running the DTC
| • | DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0157, P0158, P0160, P0161 are not set. |
| • | The Engine Run Time parameter is more than 40 seconds. |
| • | The calculated converter temperature is between 350°-585°C (662°-1085°F). |
| • | The Ignition 1 voltage parameter is between 10.5-18 volts. |
Conditions for Setting the DTC
The ECM detects that the affected HO2S calculated resistance is more than 680-5440 ohms for a corresponding calculated exhaust gas temperature.
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: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||
2 |
Does the affected HO2S voltage react immediately to the above action? | -- | Go to Step 3 | Go to Step 4 | ||||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||||||||||
4 |
Is the HO2S voltage parameter within the specified range? | 425-475 mV | Go to Step 5 | Go to Step 9 | ||||||||||||
5 |
Is the voltage less than the specified value? | 35 mV | Go to Step 6 | Go to Step 12 | ||||||||||||
6 |
Is the voltage less than the specified value? | 35 mV | Go to Step 7 | Go to Step 13 | ||||||||||||
7 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 8 | Go to Step 14 | ||||||||||||
8 | Measure the resistance of the affected HO2S heater low control circuit between the HO2S harness connector and the ECM. Refer to Circuit Testing in Wiring Systems. Is the resistance less than the specified value? | 5 ohms | Go to Step 16 | Go to Step 15 | ||||||||||||
9 | Measure the voltage from the HO2S high signal circuit on the engine harness side to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems. Is the voltage more than the specified value? | 475 mV | Go to Step 10 | Go to Step 11 | ||||||||||||
10 | Test the HO2S high signal circuit for a short to voltage or for a short to the heater low control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 | ||||||||||||
11 | Test the HO2S high signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs s in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 | ||||||||||||
12 | Test the HO2S high signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 | ||||||||||||
13 | Test the HO2S low signal circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 17 | ||||||||||||
14 | Repair the HO2S heater voltage supply circuit open or the high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- | ||||||||||||
15 | Repair the HO2S heater low control circuit open or the high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 21 | -- | ||||||||||||
16 | The HO2S is detecting a rich or lean exhaust condition or may be contaminated. Inspect for one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 18 | ||||||||||||
17 | Test for shorted terminals and poor connections at the engine control module (ECM). 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 21 | Go to Step 20 | ||||||||||||
18 | Test for shorted terminals and poor connections at the harness connector of 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 21 | Go to Step 19 | ||||||||||||
19 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 , Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 , Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 , or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 . Did you complete the replacement? | -- | Go to Step 21 | -- | ||||||||||||
20 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- | ||||||||||||
21 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 22 | ||||||||||||
22 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||
