P0134

DTC P0134:

Heated Oxygen Sensor Wiring Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a voltage of about 0.45 volt between terminals "BD2" and "BD3". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1 (1000 mV) volt if the exhaust is rich, to about 0.10 volt if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below 360°C (600°F). DTC P0131, P0132, P0134 or a cold oxygen sensor causes "Open Loop" operation.

DIAGNOSTIC TROUBLE CODE (DTC) P0134 WILL SET WHEN
^ Engine coolant temperature above 42.5°C (109°F).
^ Engine run time more than 2 minutes.
^ HO2S signal voltage is steady between 350 mV and 558 mV.
^ Throttle angle above 3%.
^ All conditions must be met for about 30 seconds.

ACTION TAKEN (PCM WILL DEFAULT TO)
With a current DTC P0134 set, the system will operate in "Open Loop." The Malfunction Indicator Lamp (MIL) (Service Engine Soon) will be illuminated.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. If the conditions for DTC P0134 exist, the system will not go into "Closed Loop."
2. This will determine if the sensor or the wiring is the cause of DTC P0134.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Check For:

Poor Connection or Damaged Harness
Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

Faulty HO2S Heater or Heater Circuit
This can be detected using the Tech 1 Scan Tool, by taking a longer period of time to go "Closed Loop." Normal "Closed Loop" operation on cold running engine is 50 seconds or warm running engine is 2 seconds. Both conditions, engine RPM must be greater 850 for 2 seconds and coolant temperature greater than 20°C. A faulty HO2S heater element or heater circuit will delay closed loop operation on cold running engine 1-2 minutes. On warm running engine it will be hard to detect. If HO2S is suspected to be faulty, disconnect the HO2S and connect test light between harness terminals "C" and "D" if the test light does not light, repair open CKT 639 or 150. If the Test light illuminates replace HO2S.