GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD (LPG) 🢒 Engine 🢒 Engine Controls - 6.0L 🢒 DTC P0134 or P0154

Circuit Description

The heated oxygen sensor (HO2S) is used in order to determine the oxygen content of the engine's exhaust. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the engine is operating lean, the exhaust will have more oxygen content. Once at operating temperature, the HO2S will produce a voltage in relation to the oxygen content of the exhaust. The HO2S requires an operating temperature of 360°C (600°F) to produce voltage. The HO2S will produce more voltage when the exhaust is rich and less voltage when the exhaust is lean. The HO2S operating voltage range is between 100 mV to 1,000 mV.

The powertrain control module (PCM) supplies a bias voltage to the HO2S. This bias voltage is around 450 mV. The Alternative Fuels ECM monitors the bias voltage as well as the voltage produced by the HO2S.

During normal Closed Loop fuel control operation, the Alternative Fuels ECM will add fuel when the HO2S indicates a lean exhaust content. When the HO2S indicates a rich exhaust content, the Alternative Fuels ECM will subtract fuel. The HO2S activity above and below the bias voltage can be monitored with a scan tool.

The oxygen sensor contains a heater. The heater is necessary in order to quickly warm the sensor to operating temperature. The heater will also maintain operating sensor temperature during extended idle conditions.

This DTC sets when a HO2S signal voltage remains within the bias range.

Conditions for Running the DTC
    • The engine is operating on alternative fuel.
    • The engine speed is more than 400 RPM.
    • The engine has been operating for at least 4 minutes.
    • The Alternative Fuels ECM determines the HO2S has been at operating temperature for at least 30 seconds. Operating temperature is indicated when engine coolant temperature is more than 40°C (104°F) AND desired gas flow is greater than 0.3 grams per second for 30 seconds.

Conditions for Setting the DTC

The Alternative Fuels ECM monitors a HO2S signal voltage stuck between 0.347 V and 0.550 V for 9 seconds continuously.

or

The Alternative Fuels ECM monitors a HO2S signal voltage between 0.00 V and 1.0 V that has not performed a Rich/Lean switch for 15 seconds continuously.

Action Taken When the DTC Sets

The Alternative Fuels ECM will control fuel trim based upon the Bank 2 Sensor 1 signal. If a Bank 2 Sensor 1 DTC sets, the Alternative Fuels ECM will operate in Open Loop fuel control.

    • A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History.
    • The Alternative Fuels ECM will illuminate the MIL and store the DTC as History after 2 consecutive drive trips that the diagnostic runs and fails.
    • The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • The Last Test Failed status will clear when the DTC runs and passes.
    • The Alternative Fuels ECM will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
    • The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
    • All DTC Information can be cleared with a scan tool.

Test Description

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

  1. This step determines if the HO2S is operating correctly. When in Closed Loop fuel control, the HO2S voltage should vary above and below the bias voltage.

    2.

  2. This step determines if the powertrain control module (PCM) and the High and Low circuits between the Control Module and the HO2S connector are operating properly.

    3.

  3. This step determines if the HO2S heater circuit operates correctly up to the HO2S connector.

    4.

  4. This step determines if the proper circuit resistance exists between the HO2S Low circuit and Control Module ground.

    5.

  5. This step determines if the proper circuit resistance exists between the HO2S Low circuit and Control Module ground with a cold sensor. A loose HO2S or faulty thread to exhaust electrical contact causes higher resistance when the HO2S is cold. Although 500 ohms is allowed, the typical resistance should be less than 50 ohms.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check Alternative Fuels - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Alternative Fuels (Engine Controls)

2

Is DTC P1215 also set?

--

Go to DTC P1215

Go to Step 3

3

  1. Use a scan tool in order to establish communication with the Alternative Fuels ECM.
  2. Capture the DTC information from the Alternative Fuels ECM into the scan tool.
  3. Clear the DTC information with the scan tool.
  4. Use the scan tool in order to reset the fuel trim value in the Alternative Fuels ECM to zero.
  5. Start and idle the engine until normal operating temperature is reached.
  6. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Does the voltage vary outside of the specified range?

300 mV-600 mV

Go to Step 4

Go to Step 5

4

The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:

    • Water intrusion of the HO2S connector
    • An intermittently open HO2S High signal circuit
    • An intermittently open HO2S Low circuit
    • An HO2S Low circuit with high resistance to ground
    • Any Alternative Fuels ECM ground circuits with high resistance
    • An inoperative HO2S heater
    • A faulty HO2S or Control Module connector terminal contact
    • An exhaust system leak up-stream of the HO2S
    • A defective HO2S

Repair any of the above conditions as necessary.

Did you find and correct the condition?

--

Go to Step 22

Go to Intermittent Conditions

5
  1. Use the scan tool in order to establish communication with the PCM.
  2. Start and idle the engine until normal operating temperature is reached.
  3. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage fixed within the specified range?

300 mV-600 mV

Go to Step 6

Go to Step 17

6

  1. Turn the ignition OFF.
  2. Disconnect the HO2S connector for the sensor that applies to this DTC.
  3. Jumper the HO2S Low circuit to a known good ground.
  4. Jumper the HO2S High signal circuit to a known good ground.
  5. Turn the ignition ON, with the engine OFF.
  6. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage less than the specified value?

20 mV

Go to Step 9

Go to Step 7

7
  1. Turn the ignition OFF.
  2. Remove the jumpers from the HO2S terminals.
  3. Disconnect the PCM connector containing the HO2S High and Low circuits.
  4. Use a digital multimeter (DMM) in order to measure the continuity of the HO2S High signal circuit and the HO2S Low circuit between the Control Module connector terminal and the HO2S connector terminal.

Are both resistances less than the specified value?

5 ohms

Go to Step 8

Go to Step 11

8

Test for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems in the C/K Pickup Service Manual.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 22

9

  1. Remove the jumpers from the HO2S terminals.
  2. Connect the J 35616-200 test lamp between the HO2S heater ignition feed and heater ground circuit terminals, engine harness side.

    3. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 12

10

  1. Turn OFF the ignition.
  2. Reconnect the HO2S connector.
  3. Disconnect the PCM connector containing the HO2S Low circuit and the PCM connector containing the PCM ground circuits.
  4. Use the DMM in order to measure the resistance between the HO2S Low circuit terminal and one of the PCM ground circuit terminals.

Is the resistance less than the specified value?

500 ohms

Go to Step 14

Go to Step 13

11

Repair the circuit that measured high resistance. Refer to Circuit Testing in Wiring Systems in the C/K Pickup Service Manual.

Did you complete the repair?

--

Go to Step 23

--

12

Repair the HO2S heater ignition or ground circuit. Probable causes include the following conditions:

    • An open circuit
    • A high circuit resistance
    • A faulty ground connection
    • An open heater fuse

Did you complete the repair?

--

Go to Step 23

--

13

Repair the high resistance between the HO2S Low circuit and the PCM ground circuit. Probable causes include the following conditions:

    • A faulty HO2S connector terminal contact
    • An open sensor harness Low circuit
    • A sensor harness Low circuit with high resistance
    • A faulty PCM ground connection
    • A high PCM ground circuit resistance
    • An ungrounded exhaust system

Did you complete the repair?

--

Go to Step 23

--

14
  1. Inspect for exhaust system leaks upstream of the suspect HO2S.
  2. Repair the exhaust as necessary.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 15

15

  1. Allow engine to cool to ambient temperature.
  2. Use the DMM in order to re-measure the resistance between the HO2S Low circuit terminal and a PCM ground circuit terminal.

Is the resistance less than the specified value?

500 ohms

Go to Step 18

Go to Step 16

16
  1. Remove the HO2S from the exhaust.
  2. Clean the HO2S mounting threads.
  3. Apply anti-seize compound GM P/N 5613695 or equivalent to the sensor threads.
  4. Install the HO2S to the proper torque. Refer to Fastener Tightening Specifications in Engine Controls in the C/K Pickup Service Manual.
  5. Use the DMM in order to measure the resistance between the HO2S Low circuit terminal and a PCM ground circuit terminal.

Is the resistance less than the specified value?

500 ohms

Go to Step 23

Go to Step 21

17
  1. Inspect the oxygen sensor signal and low circuit for continuity between the Alternative Fuels ECM connector terminals and the oxygen sensor connector terminals.
  2. Inspect these circuits for shorts to other circuits or to ground.

    3. Ensure that the oxygen sensor, PCM and the Alternative Fuels ECM connectors are disconnected before testing the circuits.

  3. Repair the wiring as necessary.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

18
  1. With a scan tool establish communications with the Alternative Fuels ECM.
  2. Observe the fuel rail pressure (FRP) sensor voltage parameter.

Does the scan tool display a FRP sensor voltage less than the specified value?

1 V

Go to DTC P0192

Go to Step 19

19

Perform the AF Fuel System diagnosis and return to this step. Refer to Fuel System Diagnosis .

Did you find and correct a CNG fuel system condition?

--

Go to Step 23

Go to Step 21

20

Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 23

--

21

Replace the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 23

--

22

Important: KL6 models require a switchover to gasoline with a scan tool in order to perform the Crankshaft Position Variation Learn Procedure.

KL8 models do not require the Crankshaft Position Variation Learn Procedure.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls in the C/K Pickup Service Manual.

Did you complete the replacement?

--

Go to Step 23

--

23
  1. Use the scan tool in order to clear the DTCs from the following control modules:
    2. • Alternative Fuels ECM
    • PCM
  2. Use the scan tool in order to reset the fuel trim value in the Alternative Fuels ECM to zero.
  3. Turn OFF the ignition for 30 seconds.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 24

Go to Step 2

24

With a scan tool, select Capture Info in order to observe the stored information.

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

--

Go to Diagnostic Trouble Code (DTC) List

System OK