Circuit Description
The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal circuits and the low signal circuits. When measured with a 10-megohm digital voltmeter, this voltage may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the HO2S 1 voltage remains excessively high for an extended period of time, DTC P0132 will be set.
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, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set. |
| • | The system voltage is more than 9 volts. |
| • | The closed loop commanded air/fuel ratio is between 14.5:1 and 14.8:1. |
| • | The throttle angle is between 3-40 percent. |
Conditions for Setting the DTC
| • | The HO2S 1 signal voltage remains more than 975 mV during normal closed loop operation. |
| OR |
| • | The HO2S 1 signal voltage remains more than 200 mV during deceleration fuel mode operation. |
| • | Either condition is present for up to 60 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
Check the following items:
| • | The fuel pressure--The system will go rich if the fuel pressure is too high. The PCM can compensate for some increase. However, if the fuel pressure is too high, a DTC P0132 may be set. Refer to Fuel System Diagnosis . |
| • | Correct Fuel Injector Operation--Refer to Fuel Injector Solenoid Coil Test . |
| • | Check the evaporative emission (EVAP) canister for fuel saturation. If the EVAP canister is full of fuel, check the canister control and hoses. Refer to DTC P0440 . |
| • | Disconnect the mass air flow (MAF) sensor and see if the rich condition is corrected. If so, replace the MAF sensor. |
| • | Check for a leaking fuel pressure regulator diaphragm by checking the vacuum line to the regulator for the presence of fuel. If a condition is found, replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement . |
| • | An intermittent throttle position (TP) sensor output will cause the system to go rich due to a false indication of the engine accelerating. The Throttle Angle displayed on a scan tool should increase steadily from 0 percent to 100 percent when opening the throttle. If not, check the TP sensor for loose mounting screws. If the TP mounting screws are OK, replace the TP sensor. Refer to Throttle Position Sensor Replacement . |
| • | If the HO2S is internally shorted, the HO2S voltage displayed on the scan tool will be over 1 volt. Disconnect the affected HO2S and jumper the HO2S low signal circuit to ground with the key ON and with the engine not running. If the displayed HO2S voltage changes from more than 1000 mV to approximately 450 mV, replace the HO2S. Silicon contamination of the HO2S can also cause a high HO2S voltage to be indicated. This condition is indicated by a powdery white deposit on the portion of the HO2S exposed to the exhaust stream. If contamination is noticed, replace the affected HO2S. Refer to Heated Oxygen Sensor 1 Replacement , or to Heated Oxygen Sensor 2 Replacement . |
| • | A poor connection or open in the HO2S high or low signal circuit can cause the DTC to set during deceleration fuel mode. An HO2S which is malfunctioning and not allowing a full voltage swing between the rich and lean thresholds can also cause this condition. Operate the vehicle while monitoring the HO2S voltage with a scan tool. If the HO2S voltage is limited within a range between 300-600 mV, check the HO2S signal, and check the low circuit wiring and the associated terminal connections. Use a corresponding mating terminal in order to test for proper terminal tension. If the wiring and the connections are OK, replace the affected HO2S. Refer to Heated Oxygen Sensor 1 Replacement , or to Heated Oxygen Sensor 2 Replacement . |
Test Description
The number below refers to the step number on the diagnostic table:
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: During this step, observe all HO2S voltage parameters. If all parameters remain below the specified value refer to Diagnostic Aids.
Does the voltage remain more than the specified value? | 975 mV | Go to Step 5 | Go to Step 3 |
Operate the vehicle in Decel fuel mode while observing the HO2S voltage parameter on the scan tool. The Decel fuel mode is when the vehicle speed more than 40 km/h (25 mph), and TP angle is less than 3 percent. Does the voltage remain more than the specified value while in Decel fuel mode? | 200 mV | Go to Step 5 | Go to Step 4 | |
4 | Operate the vehicle within the Failure Records conditions. Does the scan tool indicate this DTC failed this ignition? | -- | Go to Step 5 | Go to Diagnostic Aids |
5 | Disconnect the HO2S. Does scan tool indicate that the HO2S voltage is more than the specified value? | 500 mV | Go to Step 6 | Go to Step 8 |
6 | Test for a short to voltage on the HO2S high signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
7 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement , or to Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC run and pass? | -- | Go to Step 10 | Go to Step 2 |
10 | 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 | |
