Circuit Description
The Powertrain Control Module (PCM) supplies a reference voltage of about 0.45 volt to the Oxygen Sensor (O2S). The O2S 1 voltage varies within a range of about 1.0 volt when the exhaust is rich, down to about 0.10 volt when the exhaust is lean.
Conditions For Running The DTC
| • | No actice MAP DTC's |
| • | No active IAT DTC's |
| • | No active ECT DTC's |
| • | No active TP DTC's |
| • | No active Fuel Trim DTC's |
| • | No active Injector Control DTC's |
| • | No active Misfire DTC's |
| • | No active CKP DTC's |
| • | No active Evap DTC's |
| • | No active IAC DTC's |
| • | No active PCM Memory DTC's |
| • | Air flow is more than 3 grams per second. |
| • | Engine Coolant Temperature (ECT) is more than 70°C (158°F). |
| • | Throttle Position (TP) angle is between 4 percent and 56 percent. |
| • | The above conditions are present for 20 seconds. |
| • | Engine run time is more than 30 seconds. |
Conditions For Setting The DTC
O2S 1 voltage is between 399 mV and 499 mV for 125 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
| • | When the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor assembly must be replaced. Do not attempt to repair the wiring, the connector or the terminals. In order for the sensor to function properly, the O2S must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade the oxygen performance of the sensor. |
| • | The normal scan tool voltage varies between 150 mV to 850 mV (0.15 volt to 0.85 volt) when in a Closed Loop. The DTC P0134 sets in approximately 88 seconds when the voltage remains between 0.407 volt and 0.509 volt. The system will go into an Open Loop in about 30 seconds. |
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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This step checks for proper sensor activity. When in Closed Loop fuel control the HO2S voltage should rapidly swing above and below the bias voltage.
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This step checks the VCM and the HIGH and LOW circuits between the VCM and the HO2S connector for proper operation.
-
This step checks for proper HO2S heater circuit operation up to the HO2S connector.
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This step checks for proper circuit resistance between the HO2S LOW circuit and VCM ground.
-
This step checks for proper circuit resistance between the HO2S LOW circuit and VCM ground with a COLD sensor. A loose HO2S or poor tread 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 | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
Is the O2S voltage fixed within the voltage range specified? | 300-600 mV | |||||||||||
3 | This DTC is intermittent. Are any additional DTCs stored? | -- | Go to the applicable DTC table | Go to Diagnostic Aids | ||||||||
The leak may be very small and typically be within 12 inches of the suspect O2S. Did you find and repair a problem? | -- | |||||||||||
5 |
Is the voltage less than the specified value? | 20 mV | ||||||||||
6 |
Is the resistance of the circuit less than the specified value? | 5 ohms | ||||||||||
Did you find and repair a problem? | -- | |||||||||||
Connect a test lamp between the O2S LOW circuit (PCM side) and Battery positive terminal. Is the test lamp ON? | -- | |||||||||||
9 |
Is the resistance less than the specified value? | 5 ohms | ||||||||||
10 | Repair the circuit that measured high resistance. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||
11 | Repair the high resistance between the O2S LOW circuit and engine ground. Refer to Wiring Repairs in Wiring Systems. Probable causes include the following:
Is the action complete? | -- | -- | |||||||||
12 | Replace the O2S sensor. Refer to Oxygen Sensor Replacement Is the action complete? | -- | -- | |||||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||||
14 |
Does the scan tool indicate the diagnostic passed? | -- | ||||||||||
15 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable table | System OK |
