Circuit Description
The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen (O2) sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.
The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period, and determines if majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage for being fixed above a predetermined voltage. If the voltage is above a predetermined voltage, a DTC sets.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1258, P1415, P1416, or P1441 are not set. |
| • | The ignition 1 signal is between 9-18 volts. |
| • | The loop status is Closed. |
| • | The secondary air injection (AIR) and the catalyst diagnostics are not active. |
| • | The throttle position (TP) is between 3-70 percent. |
| • | The fuel trim learn is enabled. |
| • | The air fuel ratio is between 14.5-14.7 percent. |
| • | The fuel tank level remaining is more than 10 percent. |
Conditions for Setting the DTC
| • | The HO2S signal voltage remains above 775 mV. |
| • | The conditions exist for 31 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. |
Diagnostic Aids
Important:
• Before you service the PCM, remove any debris from the PCM connector
surfaces. When you diagnose or replace the PCM, inspect the PCM connector
gaskets. Ensure that the gaskets are installed correctly. The gaskets
prevent contaminant intrusion into the PCM. • For any test that requires probing the PCM or probing the component
harness connectors, use the J 35616
connector test adapter kit. Using this kit prevents any
damage to the harness connector terminals. Refer to
Using Connector Test Adapters
in Wiring Systems.
Inspect the following components for the following conditions:
| • | The HO2S electrical connections--Inspect the HO2S electrical connections for evidence of water intrusion. Water present in the connector causes the B+ supply to the heater to bleed over to the signal circuit. |
| • | The fuel pressure--If the pressure is too high, the system goes rich. The PCM compensates for some increase. If the fuel pressure is too high, a DTC may set. Refer to Fuel System Diagnosis . |
| • | Rich injectors--Perform the Injector Balance Test. Refer to Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool . |
| • | Leaking injectors-- Refer to Fuel System Diagnosis . |
| • | The evaporative emissions (EVAP) canister purge--Inspect for fuel saturation. If full of fuel, inspect the canister control and hoses. Refer to Evaporative Emission Control System Description . |
| • | The MAF sensor--Disconnect the MAF sensor and see if the rich condition is corrected. If the condition is corrected, inspect for proper installation. If the sensor is properly installed, replace the sensor. If the MAF sensor is installed backwards, the system goes rich. The plastic portion of the sensor has arrows that indicate the proper air flow direction. The arrows must point toward the engine. |
| • | The oxygen supply--An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or for contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. |
| • | The TP sensor--An intermittent TP sensor output causes the system to go rich, due to a false indication of the engine accelerating. |
For an intermittent condition, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a rich condition.
Before you perform this test, the engine must be at the normal operating temperature.
-
The Freeze Frame/Failure Records data may help to locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help to determine how many miles have occurred since the DTC set. The Fail Counter and the Pass Counter can also help to determine how many ignition cycles have occurred since the diagnostic reported a pass and/or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that the PCM recorded. These conditions include the RPM, the vehicle load, the vehicle speed, and the temperature.
-
If the voltage remains high, the HO2S high signal circuit is shorted to a voltage. If the voltage goes low, a rich condition exists.
-
This step isolates the condition. If the voltage remains high, the HO2S high signal circuit is not shorted to the heater feed circuit.
Step | Action | Values | Yes | No | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||||
Is the HO2S voltage more than the specified value? | 775 mV | Go to Step 4 | Go to Step 3 | |||||||||||||||
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |||||||||||||||
Is the HO2S voltage within the specified range? | 350-550 mV | Go to Step 5 | Go to Step 6 | |||||||||||||||
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 | |||||||||||||||
6 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 | ||||||||||||||
7 | 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 11 | Go to Step 9 | ||||||||||||||
8 | 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 11 | Go to Step 10 | ||||||||||||||
9 | 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 | -- | ||||||||||||||
10 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | 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 | |||||||||||||||
