P0134

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a bias voltage of about 450 mV between the HO2S signal and low circuits. When measured with a 10 megaohm Digital Multimeter, this may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1000 mV when the exhaust is rich, down through about 100 mV when the exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary. If the HO2S 1 voltage remains at or near the 450 mV bias for an extended period of time, DTC P0134 will set.

CONDITIONS FOR RUNNING THE DTC
^ No TP Sensor, EVAP System, Misfire, IAT Sensor, MAP Sensor, Fuel Trim, Fuel Injector Circuit, EGR Pintle Position, ECT Sensor, CKP Sensor, or MAF Sensor DTCs present.
^ Engine run time is longer than 200 seconds.

CONDITIONS FOR SETTING THE DTC
HO2S 1 signal voltage remains between 400 mV and 500 mV for longer than 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.
^ If the misfire is determined to be catalyst damaging, the PCM will flash the MIL.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Check for the following conditions:
^ Poor connection or damaged harness - Inspect the harness connectors for:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals Poor terminal to wire connection
- Damaged harness
^ Malfunctioning HO2S heater or heater circuit - With the ignition ON, engine not running, the HO2S voltage displayed on a scan tool should gradually drop to below 250 mV or rise to above 600 mV. If not, disconnect the HO2S and connect a test lamp between the HO2S ignition feed and heater ground circuits. If the test lamp does not illuminate, repair the open ignition feed or sensor ground circuit as necessary. Refer to Wiring Repairs. If the test lamp illuminates and the HO2S signal and low circuits are OK, replace the HO2S.
^ Intermittent test - With the ignition ON, monitor the HO2S signal voltage while moving the wiring harness and related connectors. If the malfunction is induced, the HO2S signal voltage will change. This may help isolate the location of the malfunction.

If the DTC cannot be duplicated and is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set. Also refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. When the system is operating correctly the HO2S voltage should toggle above and below the specified values.
5. If the low circuit is shorted to ground the HO2S voltage will be less than 400 mV when the signal circuit is jumped to ground.
6. The specified value is what is measured on a correctly operating system.
7. The specified value is what is measured on a correctly operating system.
14. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.