Circuit Description
Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature and 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. The ECM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The ECM will observe the activity of HO2S to determine if it has become active within a certain time period, after start-up. If the sensor has not become active within an expected time period, after start-up, the ECM will force a rich and lean state and wait for a response from the sensor. If the sensor still does not respond, a failure is reported and DTC P0135 or DTC P0155 will set. If the sensor is active within an expected time period, after engine start-up, the ECM will wait a calibrated amount of time and then begin calculating the temperature of the sensor. If the temperature of the sensor moves outside a calibrated range, a failure counter is incremented. If the number of failures exceed a calibrated amount, DTC P0135 will set for bank 1 sensor 1 or DTC P0155 will set for bank 2 sensor 1. A small reference voltage of approximately 4.5 volts is present at the heater low control circuit.
Conditions for Running the DTC
| • | DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0131, P0132, P0133, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0159, P0160, P0161, P1137, P1138, P1157, P1158, P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629, are not set. |
| • | The engine is running. |
| • | The ignition 1 signal parameter is more than 10 volts. |
| • | The HO2S Heater Bn 1 Sen. 1 or HO2S Heater Bn 2 Sen. 1 is more than 14.8 percent. |
Conditions for Setting the DTC
The HO2S has not shown the proper activity after a forced lean or rich state has been commanded for more than 25 seconds duration.
OR
The HO2S shows the proper activity, but the calculated temperature of the HO2S falls below 600°C (1,112°F) or exceeds 900°C (1,652°F), during 28 of 32 samples.
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-Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 | If DTCs P2251 or P2254 are also set, diagnose those DTCs first. Is DTC P2251, or P2254 also set? | -- | Go to DTC P2251 or P2254 | Go to Step 3 | ||||||||
3 |
Does the lambda value reach the specified value when the engine decelerates? | 1.989 | Go to Step 4 | Go to Step 5 | ||||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||||||
5 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 6 | ||||||||
6 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 | ||||||||
7 |
Refer to Circuit Testing in Wiring Systems. Is the resistance of any circuit more than the specified value? | 5 ohms | Go to Step 9 | Go to Step 8 | ||||||||
8 | Test for an intermittent and poor connections at the affected HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 | ||||||||
9 | Repair the circuits with high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||||
10 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 . Did you complete the replacement? | -- | Go to Step 11 | -- | ||||||||
11 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 12 | ||||||||
12 | 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 | ||||||||
