P0134

Schematic:

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor (HO2S) produces a voltage that varies between 100-900 mV. The Powertrain Control Module (PCM) monitors this voltage and determines by the exhaust oxygen content whether the air/fuel mixture is rich or lean. If the voltage input at the PCM is about 100 mV, the HO2S indicates a lean air/fuel mixture. If the voltage input is about 900 mV, the HO2S indicates a rich air/fuel mixture. The PCM constantly monitors the HO2S signal during closed-loop operation and compensates for an incorrect air/fuel mixture by changing the fuel-injector pulse width. A DTC P0134 will be set if the HO2S 1 voltage remains outside the active voltage range for an extended period of time.

CONDITIONS FOR RUNNING THE DTC
^ The intake air temperature is between -10°C and +70°C (14°F - 158°F).
^ The fuel tank level is above 25 percent.
^ The engine coolant temperature is more than 80°C (176°F).
^ The barometric pressure is more than 75 kPa.
^ The engine is running at a steady speed.

CONDITIONS FOR SETTING THE DTC
The HO2S voltage remains less than equal to 300 mV for at least 10 seconds.
OR
The HO2S voltage remains more than or equal to 600 mV for at least 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM records the operating conditions at the time that the diagnostic fails. This information is stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE DTC
^ The MIL turns OFF after 3 consecutive trips during which the diagnostic runs without detecting a fault.
^ A History DTC clears after 40 consecutive warm-up cycles without a fault.
^ Use the Clear DTC Information function of the scan tool, or disconnect the PCM battery feed in order to clear the DTC.

DIAGNOSTIC AIDS
Check for any of the following conditions:

DTC P0134 is likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0134.

Clear the DTCs. Road-test the vehicle while monitoring the HO2S test in the MIL/System Status selection under System Information on the scan tool. When the scan tool indicates YES, check for DTC P0134 under Last Test Failed. If DTC P0134 is not listed, the condition is intermittent, and the HO2S system diagnostic is indicating OK at this time.
^ Check for good PCM-to-engine electrical grounds.
^ A faulty HO2S. An HO2S that has a faulty internal ground circuit or an open in the signal circuit will be inactive. A contaminated HO2S. Silicon contamination of the HO2S can cause a sluggish signal voltage to be indicated.
^ Silicon contamination is indicated by a powdery white deposit on the portion of the HO2S that is exposed to the exhaust stream. Before replacing the HO2S, determine and correct the cause of the contamination. A HO2S that becomes coated with carbon or with other combustion materials may not become active, and may set DTC P0134.
^ Visually inspect the HO2S for this type of contamination. After repairing the cause of the contamination, clean the HO2S by running a warmed engine at 1,800-2,200 RPM for 2 to 3 minutes. A faulty electrical connection to the PCM
^ An intermittent malfunction may be caused by a fault in the electrical circuit of the HO2S 1.

Inspect the wiring harness and the components for any of the following conditions: Backed out terminals
^ Incorrect mating of terminals
^ Broken electrical connector locks
^ Incorrectly formed terminals or damaged terminals
^ Faulty terminal-to-wire connections
^ Physical damage to the wiring harness
^ A broken wire inside the insulation
^ Corrosion of electrical connections, of splices, or of terminals
^ If DTC P0134 cannot be duplicated, the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.