Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity for 100 seconds. During the monitor period the PCM counts the number of times that the HO2S responds from rich-to-lean and from lean-to-rich and adds the amount of time required to complete all the transitions. With this information, an average time for all the 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 the appropriate range, DTC P1134 is set, indicating 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 system voltage is more than 9 volts. |
| • | The engine is running in Closed Loop. |
| • | The engine is running for at least 60 seconds. |
| • | The engine coolant temperature (ECT) is more than 50°C (122°F). |
| • | The throttle position (TP) sensor angle is more than 2 percent. |
| • | The engine speed is between 1300 RPM and 3000 RPM. |
| • | The mass air flow (MAF) is between 13 gm/s and 29 gm/s. |
Conditions for Setting the DTC
| • | The above conditions are present for a 100 second monitoring period. |
| • | The ratio of average responses is not between 4.2 and 0.4. |
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 tests for conditions which may cause the DTC to set with a good heated oxygen sensor. Correct any 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 | |||||||||
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Important:: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding with this table.
Does the DTC set? | -- | Go to Step 3 | Go to Intermittent Conditions | |||||||||
3 | Inspect and test for the following:
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 4 | ||||||||
Visually and physically inspect the following items:
Did you find any 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 | ||||||||
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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. Important:: Determine the cause of contamination before replacing the sensor. Inspect and test for the following:
Replace the affected HO2S sensor. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement . Did you complete the repair? | -- | Go to Step 11 | -- | |||||||||
8 | Repair 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 reference circuit or grounded HO2S 1 high signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 11 | -- | ||||||||
10 | Repair open HO2S 1 high signal circuit or poor connections at the PCM. Refer to Wiring Repairs in Wiring Systems. | -- | 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 in Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||
