GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 2WD 🢒 DTC 🢒 DTC P0134 O2S Circuit Insufficient Activity Sensor 1

Object Number: 211066 Size: SF
Engine Controls Components
Cell 20: EGR Valve, EVAP and IAC Controls
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The Powertrain Control Module (PCM) supplies a reference voltage of about 0.45  volt to the Oxygen Sensor (O2S). The O2S 1 voltage varies within a range of about 1.0 volt when the exhaust is rich, down to about 0.10 volt when the exhaust is lean.

Conditions For Running The DTC
    • DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0335, P0440.P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
    • The air flow is more than 3 grams per second.
    • The engine coolant temperature (ECT) is more than 70°C (158°F).
    • The throttle position (TP) angle is between 4 percent and 56 percent for 20 seconds.
    • The engine run time is more than 30 seconds.

Conditions For Setting The DTC

The O2S 1 voltage is between 399 mV and 499 mV for 125 seconds.

Action Taken When the DTC Sets
    • The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction active.
    • The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
    • A history DTC stores.

Conditions for Clearing the MIL/DTC
    • The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm up cycles without a fault.
    • Use a scan tool to clear the DTCs.

Diagnostic Aids
    • When the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor assembly must be replaced. Do not attempt to repair the wiring, the connector or the terminals. In order for the sensor to function properly, the O2S must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade the oxygen performance of the sensor.
    • The normal scan tool voltage varies between 150 mV to 850 mV (0.15 volt to 0.85 volt) when in a Closed Loop. The DTC P0134 sets in approximately 88 seconds when the voltage remains between 0.407 volt and 0.509 volt. The system will go into an Open Loop in about 30 seconds.

Test Description

The number(s) below refer(s) to the step number(s) on the Diagnostic Table.

  1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The scan tool stores this data for later reference.

    2.

  2. During the engine warm-up, the O2S 1 should warm-up and the voltage output should vary between 150 mV and 850 mV. When the O2S 1 voltage varies, the engine will go into a Closed Loop operation. This step determines if the O2S 1 sensor is operating properly.

    3.

  3. This step will determine if the O2S 1 sensor is malfunctioning, or if the wiring or the PCM is the cause of the DTC P0134.

    4.

  4. Use only a high impedance digital volt ohmmeter for this test. This test checks the continuity of O2S 1 sensor signal circuit and the O2S 1 sensor low circuit; if the O2S 1 sensor low circuit is open, and if the PCM voltage on the O2S 1 sensor signal circuit will be over 0.6 volt (600 mV).

    5.

  5. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communication System (ITCS) information for PCM programming and the Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

DTC P0134-Oxygen Sensor (O2S) Circuit Insufficient Activity Detected (Sensor 1)

Step

Action

Value(s)

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Install a scan tool.
  2. Start the engine.
  3. Run the engine above the specified operating temperature.
  4. Operate the engine above the specified RPM for 2 minutes.

Does the scan tool indicate a Closed Loop operation?

80°C (176°F)

1,200 RPM

Go to Step 3

Go to Step 4

3
  1. Review the Freeze Frame data and record the parameters.
  2. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting The DTC as specified.

Does the scan tool indicate a Closed Loop operation?

--

Go to Step 12

Go to Step 4

4

    Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

  1. Turn OFF the ignition switch.
  2. Disconnect the O2S 1 sensor electrical connector.
  3. Turn ON the ignition switch leaving the engine OFF.
  4. Connect a jumper wire to the O2S 1 sensor signal circuit terminal (PCM side) to ground.

Is the O2S 1 voltage below the specified value?

50 mV (0.05 V)

Go to Step 5

Go to Step 6

5
  1. Turn OFF the ignition switch.
  2. Check for the following conditions in the O2S 1 electrical connector (PCM side):
    3. • Terminal connections
    • Poor electrical connections
  3. Repair the malfunctioning terminals or the poor electrical connection as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 9

6

  1. Remove the jumper wire.
  2. Connect a DMM to ground.
  3. Measure the voltage between the O2S 1 sensor signal circuit terminal (PCM side) and the ground.

Does the O2S 1 voltage measure above the specified value?

600 mV (0.6 V)

Go to Step 10

Go to Step 7

7

Does the O2S 1 voltage measure below the specified value?

300 mV (0.3 V)

Go to Step 11

Go to Step 8

8

  1. Turn OFF the ignition switch.
  2. Replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 12

--

9

Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

Replace the O2S 1 sensor. Refer to the Oxygen Sensor Replacement .

Is the action complete?

--

Go to Step 12

--

10
  1. Turn OFF the ignition switch.
  2. Check for the following conditions in the O2S 1 sensor ground circuit:
    3. • Open circuit
    • Poor electrical connection
  3. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

11
  1. Turn OFF the ignition switch.
  2. Check for the following conditions in the O2S 1 sensor signal circuit:
    3. • Open circuit
    • Poor electrical connection
  3. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 12

Go to Step 8

12
  1. Reconnect the O2S 1 electrical connector if the connector is disconnected.
  2. Turn ON the ignition switch leaving the engine OFF.
  3. Clear the DTCs with the scan tool.
  4. Start the engine.
  5. Idle the engine at the normal operating temperature.
  6. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has ran and passed?

--

Go to Step 13

Go to Step 2

13

Check to see if any additional DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to applicable DTC table

System OK