Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal . Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays above the specified value, DTC P0138 or P0158 sets.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 are not set. |
| • | The Ignition 1 Signal parameter is between 9-18 volts. |
| • | The fuel level parameter is more than 10 percent. |
| • | The Loop Status parameter is Closed. |
Rich Test Enable
| • | The air fuel ratio is between 14.5:1-14.7:1. |
| • | The TP indicated angle parameter is between 3-70 percent more than the value observed at idle. |
Decel Fuel Cut-off Test Enable
| • | Decel fuel cut-off is active. |
| • | The above condition is met for 10 seconds. |
Conditions for Setting the DTC
Rich Test
The affected HO2S voltage parameter is more than 930 mV for 200 seconds.
Decel Fuel Cut-off Test
The affected HO2S voltage parameter is more than 480 mV for 5 seconds.
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 DTC also sets during a deceleration fuel cut-off. Inspect for conditions such as leaking or stuck injectors, which could cause a rich exhaust during a deceleration.
The engine must be at the normal operating temperature before you perform this test.
-
If the voltage remains high, this indicates that the signal circuit is shorted to a voltage.
Step | Action | Value(s) | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to | ||||||||||||||
Is the HO2S voltage more than the specified value? | 930 mV | Go to Step 5 | Go to Step 3 | |||||||||||||||
3 |
Is the HO2S voltage within the specified range? | 410-490 mV | Go to DTC P0140 or P0160 | Go to Step 4 | ||||||||||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||||||||||||
Is the HO2S voltage within the specified range? | 350-550 mV | Go to Step 6 | Go to Step 7 | |||||||||||||||
6 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 8 | ||||||||||||||
7 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | ||||||||||||||
8 | Inspect for 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 12 | Go to Step 10 | ||||||||||||||
9 | Inspect for poor connections at the harness connector of the 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 12 | Go to Step 11 | ||||||||||||||
10 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||||||
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||||||||
12 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 13 | ||||||||||||||
13 | Observe the Capture Info with the scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||||
