Circuit Description
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high, and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.
The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or "lean-out" the mixture, when the HO2S detects a rich exhaust condition.
Certain vehicle models utilize an oxygen sensor behind the catalytic converter in order to monitor catalyst efficiency.
This diagnostic trouble code (DTC) determines if the HO2S is functioning properly. The DTC checks for an adequate number of HO2S voltage transitions above and below the bias range of 300-600 mV. This DTC sets when the powertrain control module (PCM) fails to detect a minimum number of voltage transitions above and below the bias range during the test period.
Conditions for Running the DTC
| • | DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0128, P0200, P0300, P0351-P0358, P0401, P0404, P0405, P0410, P0418, P0443, P0446, P0449, P1120, P1220, P1221, P1258, or P1404 are not set. |
| • | The secondary air injection (AIR) and the exhaust gas recirculation (EGR) diagnostics are not active. |
| • | The system voltage is above 9 volts. |
| • | The system is in a Closed Loop. |
| • | The engine coolant temperature (ECT) is more than 57°C (135°F). |
| • | The engine has been running for more than 160 seconds. |
| • | The mass air flow (MAF) is between 15-55 g/s. |
| • | The engine speed is between 1,100-3,000 RPM. |
| • | The evaporative emission (EVAP) canister purge is active. |
| • | The accelerator pedal position (APP) indicated angle is above 5 percent. |
Conditions for Setting the DTC
The PCM determines that the HO2S transition time ratio is not at the expected value.
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
| • | Using the Freeze Frame/Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame/Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass or a fail. Operate vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed. |
| • | An oxygen supply inside the HO2S is necessary for proper operation. This supply of oxygen is provided through the HO2S wires. All HO2S wires and connections should be inspected for breaks or contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. |
For an intermittent, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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When DTCs P1134 and P1154 are set at the same time, this is a good indication that a fuel contamination condition is present.
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The use of leaded fuel may be indicated by the removal or tampering of the fuel filler restrictor. An HO2S contaminated by silicone will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of the contamination is the use of unapproved silicone RTV engine gasket material or the use of silicone-based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also be contaminated.
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Even small exhaust leaks can cause a slow response from the HO2S.
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An HO2S contaminated by silicone will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of the contamination is the use of unapproved silicone RTV engine gasket material or the use of silicone-based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also be contaminated.
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If the voltage observed in Step 8 is less than the range specified, a short between the high and low circuits or a short between the high circuit and ground is indicated. With the HO2S and the PCM disconnected the resistance between the high and low circuits and the resistance between the high circuit and ground should measure infinite. If the voltage observed in Step 8 is more than the range specified a short between the high circuit and a voltage source is indicated.
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If the voltage observed in step 9 is not below the voltage specified, a high resistance in the high or low circuit is indicated. Good circuit continuity measures less than 5 ohms with the PCM and sensor disconnected. Measure between the PCM connector and the HO2S connector. Ensure that the PCM terminal contact is good.
Step | Action | Values | Yes | No | ||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||||||||||||||||||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||||||||||||||||||||||||
In addition to this DTC, check for the following HO2S DTCs:
Are any of the above listed DTCs set? | -- | Go to Step 4 | Go to Step 3 | |||||||||||||||||||||||||||||
3 | Are there any other DTCs set? | -- | Go to Step 5 | |||||||||||||||||||||||||||||
Has the source of contamination been removed and the affected sensors replaced? | -- | Go to Step 14 | Go to Step 5 | |||||||||||||||||||||||||||||
5 |
Did the DTC run and fail this ignition? | -- | Go to Step 7 | Go to Step 6 | ||||||||||||||||||||||||||||
6 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Did you find and correct the condition? | 350-550 mV | Go to Step 18 | Go to Diagnostic Aids | ||||||||||||||||||||||||||||
Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 8 | |||||||||||||||||||||||||||||
8 |
Does the HO2S voltage measure within the specified range? | 351-551 mV | Go to Step 9 | Go to Step 13 | ||||||||||||||||||||||||||||
9 |
Does the HO2S voltage measure within the specified range? | 20 mV | Go to Step 10 | Go to Step 14 | ||||||||||||||||||||||||||||
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 15 | ||||||||||||||||||||||||||||
11 |
Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 16 | ||||||||||||||||||||||||||||
Did you complete the repair? | -- | Go to Step 17 | -- | |||||||||||||||||||||||||||||
Did you find and correct the condition? | -- | Go to Step 18 | Go to Diagnostic Aids | |||||||||||||||||||||||||||||
Did you complete the repair? | -- | Go to Step 18 | -- | |||||||||||||||||||||||||||||
15 | Repair the heater high control circuit to the HO2S heater. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- | ||||||||||||||||||||||||||||
16 | Repair the heater low control circuit to the HO2S heater. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 18 | -- | ||||||||||||||||||||||||||||
17 | Replace the appropriate 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 18 | -- | ||||||||||||||||||||||||||||
18 |
Does the DTC run and pass? | -- | Go to Step 19 | Go to Step 2 | ||||||||||||||||||||||||||||
19 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||||||||||||||||||||||
