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 the 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, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, 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 fuel tank level remaining is more than 10 percent. |
| • | The loop status is closed. |
| • | Intrusive tests are not in progress. |
| • | Scan tool output controls are not active. |
Rich Test Enable
| • | The air fuel ratio is between 14.5:1 and 14.7:1. |
| • | The throttle position (TP) is between 3-70 percent. |
Decel Fuel Cut-Off Test Enable
| • | Decel fuel cut-off is active. |
| • | The above condition is met for 1 second. |
Conditions for Setting the DTC
Rich Test
The HO2S voltage is more than 775 mV for 165 seconds.
Decel Fuel Cut-Off Test
The HO2S voltage is more than 540 mV for 5 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the seconds 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. |
| • | The control module commands Open Loop. |
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.
-
If the voltage is above the specified value, the condition is present.
-
If the voltage remains high, the HO2S high signal circuit is shorted to a voltage.
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 | |||||||||||||||
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 | |||||||||||||||
5 |
Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 | ||||||||||||||
6 |
Notice: A short to voltage on the heated oxygen sensor (HO2S) high signal circuit may damage the HO2S. 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 | |||||||||||||||
