P0134

CIRCUIT DESCRIPTION
The VCM supplies a voltage of about 0.45 volt between the HO2S High and the HO2S Low circuits. (If measures with a 10 megaohm digital voltmeter, this may read as low as 0.32 volt.) The Heated Oxygen Sensor (HO2S Bank 1, Sensor 1) varies the voltage within a range of about 1.0 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 360°C (600°F). An open oxygen sensor circuit or cold oxygen sensor causes an Open Loop operation.

The HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during a long extended idle.

The DTC P0134 determines if the HO2S at the HO2S circuit has developed an open. This DTC is a type A DTC.

CONDITIONS FOR SETTING THE DTC
The following conditions will set the DTCs:

^ No TP sensor DTCs.
^ No Evaporative Emissions (EVAP) DTCs.
^ No IAT sensor DTCs.
^ No MAP sensor DTCs.
^ No ECT sensor DTCs.
^ No MAF sensor DTCs.
^ No intrusive test in progress.
^ No device controls active.
^ The system voltage measures at least 9.0 volts. The engine run time is greater than 2 minutes.

HO2S Sensor Open Test Enable

^ The engine run time is greater than 2 minutes.
^ A Closed Loop exists.
^ The DTC P0135 (HO2S Bank 1, Sensor 1 heater) is not set.
^ The HO2S (Bank 1, Sensor 1) voltage is greater than 0.299 volts (299 mV) but less than 0.598 volts (598 mV).

ACTION TAKEN WHEN THE DTC SETS
With a current DTC set, the system operates in an Open Loop. The Malfunction Indicator Lamp (MIL) turns on.

CONDITIONS FOR CLEARING THE MIL/DTC
The VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

DIAGNOSTIC AIDS
A poor connection, rubbed through wire insulation, or a wire broken inside the insulation may cause an intermittent.

Check for the following conditions:

^ A poor connection or a damaged harness: Inspect the harness connectors for the following conditions:

- Backed out terminals.
- Improperly formed or damaged terminals.
- Poor terminal to wire connection.
- Damaged harness.

^ A faulty HO2S (Bank 1, Sensor 1) heater or heater circuit: With the ignition switch turned on but the engine stays off, the HO2S (Bank 1, Sensor 1) voltage displayed on a scan tool should gradually drop to below 0.150 volt, indicating that the heater works properly. If not, disconnect the HO2S (Bank 1, Sensor 1) and connect a test lamp between the terminals C and D. If the test lamp does not light, repair the open in the HO2S (Bank 1, Sensor 1) ground circuit or the HO2S (Bank 1, Sensor 1) ignition feed circuit. If the test lamp lights, replace the HO2S (Bank 1, Sensor 1).
^ The Intermittent test: With a scan tool monitor the HO2S (Bank 1, Sensor 1) signal voltage while moving the related connectors and the wiring harness with a warm engine running at part throttle in a Closed Loop. If the failure is induced, the HO2S (Bank 1, Sensor 1) signal voltage reading changes from its normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help to isolate the location of the malfunction.

Never solder the HO2S wires. For proper wire and connection repairs, refer to Wiring Repairs.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.

2. If the conditions for setting the DTC P0134 exist, the system will not go into a Closed Loop.
3. This test determines if the sensor or the wiring is the cause of the DTC P0134.
4. This test checks the continuity of the HO2S 1 signal circuit.