Circuit Description
The powertrain control module (PCM) supplies a voltage of 0.45 volt between terminals J1-13 and J1-14. If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt. The oxygen sensor (O2S) 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 it is below 315°C (600°F). An open sensor circuit or a cold sensor causes Open Loop operation.
If the oxygen sensor pigtail wiring, connector, or terminal are damaged, the entire O2S assembly must be replaced. DO NOT attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the O2S wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degrade O2S performance. Refer to Section 8A-5, Heated Oxygen Repair.
Conditions for Setting
| • | When one or more of the following DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0441, P0562, P563, P1171, P1441 are not present. |
| • | The O2S voltage is between 407-509 mV. |
| • | The engine has been running for at least 60 seconds. |
| • | TP angle is between 5-50 percent. |
| • | The above conditions are present for at least 38 seconds. |
Action Taken
| • | Malfunction indicator lamp (MIL) illuminates after one driving cycle with the fault active. |
| • | Vehicle will operate in Open Loop. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic tests. |
| • | A history DTC will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTCs can be cleared by using a scan tool. |
Diagnostic Aids
| • | Normal scan tool voltage varies between 150-850 mV (0.15-0.85 volt) while in Closed Loop. DTC P0134 sets in approximately 88 seconds if the voltage remains between 0.407-0.509 volt, but the system will go into Open Loop in about 30 seconds. |
| • | If DTC P0134 is intermittent, refer to Symptoms Section. |
Test Description
The number below refers to the step number on the diagnostic table.
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During engine warm-up, the O2S 1 should warm-up and its voltage output should vary between 150-850 mV. When O2S 1 voltage varies, the engine will go into Closed Loop. This step determines if the O2S 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).
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |
Does the scan tool indicate O2S 1 voltage varying outside the specified values? | 407-509 mV | Go to Step 4 | Go to Step 3 | |
3 |
Does O2S 1 voltage stay above the specified range? | 407-509 mV | Go to Step 4 | Go to Diagnostic Aids |
Is the O2S 1 voltage below the specified value? | 200 mV | Go to Step 8 | Go to Step 5 | |
Does the O2S 1 voltage measure above the specified value? | 407 mV | Go to Step 6 | Go to Step 7 | |
6 |
Was an O2S 1 low circuit problem found and corrected? | -- | Go to Step 9 | |
7 |
Was an O2S 1 signal circuit problem found and corrected? | -- | Go to Step 10 | |
8 | Inspect for a poor O2S 1 signal or low circuit terminal connection at the O2S 1 harness connector and replace terminals, if necessary. Did any terminals require replacement? | -- | Go to Step 11 | |
9 | Inspect for poor O2S 1 low circuit terminal connection at the PCM and replace terminal if necessary. Did the terminal require replacement? | -- | Go to Step 12 | |
10 | Inspect for poor O2S 1 signal circuit terminal connection at the PCM and replace terminal if necessary. Did the terminal require replacement? | -- | Go to Step 12 | |
11 | Replace the O2S 1. Is the action complete? | -- | -- | |
12 | Replace the PCM. Is the action complete? | -- | -- | |
