The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the HO2S low signal circuit. When measured with a 10 mega ohm DMM, this may display as low as 350 mV. The oxygen sensor signal varies from about 1,000 mV when the exhaust is rich, to about 100 mV when the exhaust is lean. If the HO2S 1 voltage remains at or near the 450 mV bias for an extended period of time, DTC P0134 is set.
If the signal amplitude of HO2S bank 1 sensor exceeds the lack of activity thresholds but will not allow Closed Loop operation, DTC P0130 will set.
• | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201-P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set. |
• | The engine running for at least 4 minutes. |
• | The engine coolant temperature is at least 50°C (122°F). |
• | The engine RPM is between 1,000-3,000 RPM. |
• | The air flow is between 13-30 grams per second. |
• | The accelerator pedal position (APP) indicated angle is between 5-40 percent. |
• | The ignition voltage is more than 9 volts, and less than 18 volts. |
The PCM detects an active sensor with an improper HO2S voltage amplitude.
• | 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. |
• | 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. |
The numbers below refer to the step numbers on the diagnostic table.
This step checks for proper sensor activity. HO2S voltage should rapidly swing above and below the range specified.
This step checks the PCM and the high and low signal circuits between the PCM and the HO2S connector for proper operation.
This step checks for proper HO2S heater circuit operation up to the HO2S connector.
This step checks for proper circuit resistance between the HO2S low signal circuit and PCM ground.
This step checks for proper circuit resistance between the HO2S low signal circuit and PCM ground with a COLD sensor. A loose HO2S or poor thread to exhaust electrical contact will cause higher resistance when the HO2S is cold. Although 500 ohms is allowed, typical resistance should be less than 50 ohms.
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 fixed within the voltage range specified? | 300-600 mV | Go to Step 4 | Go to Step 3 | |||||||||||||||||||
3 |
Did you find and correct the condition? | -- | Go to Step 17 | Go to Intermittent Conditions | ||||||||||||||||||
Does the voltage measure less than the specified value? | 20 mV | Go to Step 7 | Go to Step 5 | |||||||||||||||||||
5 |
Does the resistance of both circuits measure less than the specified value? | 5 ohms | Go to Step 6 | Go to Step 9 | ||||||||||||||||||
6 | Inspect for poor connections at the harness connector of the PCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||||||||||||
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 10 | |||||||||||||||||||
Does the resistance measure less than the specified value? | 500 ohms | Go to Step 12 | Go to Step 11 | |||||||||||||||||||
9 | Repair the circuit that measured high resistance. Did you complete the repair? | -- | Go to Step 17 | -- | ||||||||||||||||||
10 | Repair the HO2S Heater ignition 1 voltage or heater ground circuit. Probable causes include the following conditions:
Did you complete the action? | -- | Go to Step 17 | -- | ||||||||||||||||||
11 | Repair the high resistance between the HO2S low signal circuit and the PCM ground circuit. Probable causes include the following conditions:
Did you complete the repair? | -- | Go to Step 17 | -- | ||||||||||||||||||
12 |
The leak may be very small and will typically be within 30.5 mm (12 inches) of the suspect HO2S. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 | ||||||||||||||||||
Does the resistance measure less than the specified value? | 500 ohms | Go to Step 15 | Go to Step 14 | |||||||||||||||||||
14 |
Does the resistance measure less than the specified value? | 500 ohms | Go to Step 17 | Go to Step 15 | ||||||||||||||||||
15 | Replace the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 , 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 17 | -- | ||||||||||||||||||
16 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||||||||||||
17 |
Does this DTC run and pass? | -- | Go to Step 18 | Go to Step 2 | ||||||||||||||||||
18 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTC' that you have not diagnosed? | -- | System OK |