Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity. The PCM counts the number of times that the HO2S responds by switching from a rich state to a lean state. Next, the PCM adds the amount of time the HO2S took to complete all transitions during the 100-second test period. With this information, an average time for all transitions can be determined. The PCM then divides the rich-to-lean average by the lean-to-rich average to obtain a ratio. If the HO2S transition time ratio is not within range, this diagnostic trouble code (DTC) will set. The setting of this DTC indicates that the oxygen sensor is not responding as expected, to changes in exhaust oxygen content.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set. |
| • | The mass air flow (MAF) is between 10-30 g/s. |
| • | The engine coolant temperature (ECT) is more than 50°C (122°F). |
| • | The engine run time is more than 60 seconds. |
| • | The engine speed is between 1,000-3,000 RPM. |
| • | The engine is running in Closed Loop. |
Conditions for Setting the DTC
| • | The above conditions are present for a 100-second monitoring period. |
| • | For VIN K, the ratio of average response times is not between 3.5-0.5. |
| • | For VIN 1, the ratio of average response times is not between 6-0.5. |
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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step test for conditions which may cause the DTC to set with a good heated oxygen sensor. Correct any of the described conditions, if present.
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Before replacing the HO2S, inspect for silicon contamination.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||
2 |
Important: If any DTCs are set except P1133 or P1134, go to those DTCs before proceeding with this diagnostic table.
Does the DTC reset? | -- | Go to Step 3 | Go to Intermittent Conditions | ||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 4 | ||||||||
Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 5 | |||||||||
5 |
Does the voltage measure near the specified value? | 450 mV | Go to Step 6 | Go to Step 9 | ||||||||
6 |
Does the voltage measure less than the specified value? | 300 mV | Go to Step 7 | Go to Step 10 | ||||||||
|
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor. Replace the affected HO2S. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- | |||||||||
8 | Repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||||
9 | Repair the open HO2S 1 low signal circuit or the grounded HO2S 1 high signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||||
10 | Repair the open HO2S 1 high signal circuit or the poor connections at the PCM. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||||
11 |
Does the DTC run and pass? | -- | Go to Step 12 | Go to Step 2 | ||||||||
12 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
