GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Express (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC P0132 or P0152

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 0.10 volts (100 mV) to 1 volt (1,000 mV).

The gasoline Control Module (VCM/PCM or ECM) supplies a bias or reference voltage to the HO2S. This bias voltage is around 450 mV.

This DTC is used to indicate an HO2S signal voltage that is above the normal operating range of the sensor.

Conditions for Running the DTC
    • The engine is operating on alternative fuel.
    • The engine speed is more than 400 RPM.
    • The engine coolant temperature (ECT) is above 70°C (160°F).
    • 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.
    • The Alternative Fuels ECM is operating in Closed Loop fuel control.

Conditions for Setting the DTC

The Alternative Fuels ECM monitors an HO2S signal voltage of more than 1 volt (1,000 mV) for 3 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.

Diagnostic Aids

Intermittent Condition

A fault not present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to the Intermittent Conditions diagnostic information located in Symptoms - Engine Controls. If any additional DTCs were stored proceed to the applicable DTC table in the order stated in Diagnostic System Check - Alternative Fuels (Engine Controls) .

Test Description

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

  1. An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of unapproved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also be contaminated.

    2.

  2. An HO2S contaminated by silicon will have a white, powdery deposit on the portion of the HO2S that is exposed to the exhaust stream. The usual cause of silica contamination is the use of unapproved silicon RTV engine gasket material or the use of silicon based sprays or fluids within the engine. If the cause of this contamination is not corrected, the replacement HO2S will also be contaminated.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

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

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Go to Step 2

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

2
  1. Run the engine until a normal operating temperature is reached.
  2. Use a scan tool in order to establish communication with the Alternative Fuels ECM.
  3. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage fixed at more than the specified value?

1,000 mV

Go to Step 5

Go to Step 3

3

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

    • A signal wire intermittently shorted to voltage
    • Water intrusion of the HO2S connector
    • A silicon contaminated HO2S
    • An intermittent rich engine condition such as the following:
       - An EVAP canister purge system malfunction
       - Gasoline contaminated engine oil
       - An incorrect fuel pressure
       - A leaking gasoline fuel pressure regulator
       - An inaccurate MAF sensor
    • Repair any of the above or similar engine conditions as necessary.

Was a condition found and repaired?

--

Go to Step 15

Go to Step 4

4

The fault is not present. Refer to Diagnostic Aids.

Are any DTCs stored that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Intermittent Conditions

5
  1. Run the engine until a normal operating temperature is reached.
  2. Use the scan tool in order to establish communication with the gasoline Control Module (VCM/PCM or ECM).
  3. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage fixed at more than the specified value?

1 V

Go to Step 6

Go to Step 12

6
  1. Turn the ignition OFF.
  2. Disconnect the Alternative Fuels ECM connectors.
  3. Run the engine until a normal operating temperature is reached.
  4. Use the scan tool in order to monitor the HO2S voltage for the sensor that applies to this DTC.

Is the voltage fixed at more than the specified value?

1 V

Go to Step 7

Go to Step 11

7
  1. Turn the ignition OFF.
  2. Disconnect the HO2S connector for the sensor that applies to this DTC.
  3. Leave the Alternative Fuels ECM disconnected.
  4. Jumper the HO2S Low circuit terminal - engine harness side 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 within the specified range?

351-551 mV

Go to Step 8

Go to Step 9

8

  1. The HO2S is detecting a rich exhaust condition or may be contaminated. Inspect for one of the following conditions:
    2. • Water intrusion of the HO2S connector
    • A silicon contaminated HO2S
    • Fuel contaminated engine oil
    • An EVAP canister purge system malfunction
    • An incorrect fuel pressure
    • A leaking gasoline fuel pressure regulator
    • An inaccurate MAF sensor
  2. Repair any of the above or similar engine conditions as necessary.

Was a condition found and repaired?

--

Go to Step 15

Go to Step 13

9
  1. Turn the ignition OFF.
  2. Remove the jumper from the HO2S Low circuit terminal.
  3. Disconnect the HO2S High signal circuit from the gasoline Control Module (VCM/PCM or ECM) connector.
  4. Turn the ignition ON, with the engine OFF.
  5. Use a digital multimeter (DMM) in order to measure the voltage between the HO2S High signal circuit terminal - harness side and ground.

Is the voltage more than the specified value?

20 mV

Go to Step 10

Go to Step 14

10

Repair the HO2S signal High circuit short to voltage.

Is the action complete?

--

Go to Step 15

--

11

The HO2S may be detecting a rich exhaust condition only during CNG operation.

Perform the Fuel System Diagnosis and return to this step.

Was a rich AF fuel system condition found and repaired?

--

Go to Step 15

Go to Step 12

12
  1. Replace the Alternative Fuels ECM. Refer to Alternative Fuels Engine Control Module Replacement .
  2. Program the replacement Control Module with the correct vehicle software and calibration.

Did you complete the repair?

--

Go to Step 15

--

13

Replace the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 in the Engine Controls section of the G Van Service Manual.

Did you complete the repair?

--

Go to Step 15

--

14

Important: The following Control Module replacement procedures must all be completed before attempting to operate the vehicle.

The following procedures are located in the G Van Service Manual.

  1. Replace the gasoline Control Module (VCM/PCM or ECM). Refer to Powertrain Control Module Replacement .
  2. Program the replacement Control Module with the correct vehicle software and calibration.

    3. Important: In order to perform the variation learn procedure, a switch to gasoline operation is necessary. Remove the CNG 20-amp fuse in order to perform the switch.

  3. Perform the Crankshaft Position System Variation Learn .

Did you complete the repair?

--

Go to Step 15

--

15
  1. Reconnect all disconnected or removed components.
  2. Use the scan tool in order to clear all DTC information from BOTH the gasoline Control Module (VCM/PCM or ECM) and the Alternative Fuels ECM.
  3. Use the scan tool in order to communicate with the BOTH the gasoline Control Module and the Alternative Fuels ECM in order to reset the Fuel Trim values to zero.
  4. Start the engine.
  5. Operate the vehicle within the Conditions for Running the DTC until the scan tool indicates the diagnostic ran.

Does the scan tool indicate the diagnostic passed?

--

System OK

Go to Step 2