Circuit Description
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volt between the O2S signal and the ground circuit. The Oxygen Sensor (O2S 1) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volt if the exhaust is lean.
The sensor is like an open circuit and produces no voltage when below 315°C (600°F). An open sensor circuit or a cold sensor causes an Open Loop operation.
If there is damage to the oxygen sensor pigtail wiring, the connector or the terminal, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, the connector or the terminals. The sensor must have a clean air reference provided in order to function properly. This clean air reference is obtained by way of the oxygen sensor wire(s). Any attempt to repair the wires, the connectors or the terminals could result in the obstruction of the air reference and degrade the oxygen sensor performance. Refer to Heated Oxygen Sensor (O2S) Repair.
Conditions For Setting The DTC
| • | DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441 not set. |
| • | Engine run time is greater than 30 seconds. |
| • | Engine Coolant Temperature (ECT) is greater than 70°C (158°F). |
| • | Throttle Position (TP) angle is between 8% and 56% for 20 seconds. |
| • | O2S 1 voltage is between 399 mV and 499 mV for 125 seconds. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
| • | The vehicle will operate in an Open Loop operation. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm-up cycles without a fault. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
The normal scan tool voltage varies between 150 mV to 850 mV (0.15 volt to 0.85 volt) while in a Closed Loop operation.
An intermittent could be the result of the following conditions:
| • | A poor electrical connection |
| • | Rubbed-through wire insulation |
| • | A broken wire inside the insulation |
Check for a poor electrical connection or a damaged harness. Inspect the harness electrical connectors for the following conditions:
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed electrical connectors |
| • | Damaged terminals |
| • | A poor terminal-to-wire connection |
| • | A damaged harness |
Replace the entire oxygen sensor (O2S 1) assembly. Do not attempt to repair the oxygen sensor if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | Damaged terminals |
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.
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During engine warm-up, the O2S 1 should warm-up and its voltage output should vary between 150 mV and 850 mV. When O2S 1 voltage varies, the engine will go into Closed Loop . This step determines if the O2S 1 is operating properly.
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This will determine if the sensor is at fault or the wiring or PCM is the cause of the DTC P0134.
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Use only a high impedance digital volt ohmmeter for this test. This test checks the continuity of CKT 412 and CKT 413; if CKT 413 is open, the PCM voltage on CKT 412 will be over 0.6 volt (600 mV).
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Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||
Does the scan tool indicate Closed Loop? | 80°C (176°F) 1200 RPM | |||
3 |
Does the scan tool indicate Closed Loop? | -- | ||
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Is the O2S 1 voltage below the specified value? | 200 mV (0.2V) | |||
5 |
Was a repair necessary? | -- | ||
Does the O2S 1 voltage measure above the specified value? | 600 mV (0.6V) | |||
7 | Does the O2S 1 voltage measure below the specified value? | 300 mV (0.3V) | ||
Replace the PCM. Is the action complete? | -- | -- | ||
9 | Replace the O2S 1 sensor. Is the action complete? | -- | -- | |
10 | Check the O2S 1 sensor ground circuit for an open or poor connection and repair as necessary. Was a repair necessary? | -- | ||
11 | Check the O2S 1 sensor signal circuit for an open or poor connection and repair as necessary. Was a repair necessary? | -- | ||
12 |
Does the scan tool indicate that this diagnostic has ran and passed? | -- | ||
13 | Check if any additional DTC's are set. Are any DTC's displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
