GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Express (CNG) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 DTC P0107

Circuit Description

The manifold absolute pressure (MAP) sensor is a pressure sensor. The gasoline Control Module (VCM / PCM or ECM) supplies about 5 volts on the MAP sensor reference voltage circuit. The gasoline Control Module also supplies a ground circuit to the MAP sensor. When the manifold vacuum is low, the MAP signal voltage rises to near 4.5 volts. As the manifold vacuum increases, the MAP signal voltage drops to around 1 volt. The gasoline Control Module and the Alternative Fuels ECM monitor the MAP signal circuit voltage and determine the vacuum within the intake manifold.

Certain vehicle models will also use the MAP sensor in order to determine the barometric pressure (BARO) when the ignition switch is turned ON and the engine is NOT cranked. This BARO reading may also be updated whenever the engine is operated at wide open throttle (WOT).

This DTC is used to indicate a MAP sensor signal voltage that is below the normal operating range of the sensor.

Conditions for Running the DTC
    • The engine is operating on alternative fuel.
    • The engine speed is greater than 500 RPM.
    • DTCs P0121, P0122, or P0123 are not set.
    • The TP angle is less than 4 percent when engine speed is less than 1,200 RPM.
        or
        The TP angle is greater than 20 percent when engine speed is greater than 1,300 RPM.

Conditions for Setting the DTC

The Alternative Fuel ECM monitors a MAP sensor signal voltage of less than 0.098 volts for at least 4 seconds continuously.

Action Taken When the DTC Sets
    • The Alternative Fuel ECM will switch-over to gasoline fuel operation.
    • The Alternative Fuel ECM will not attempt alternative fuel operation until the next key cycle.
    • 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. This step determines if the failure condition affects the gasoline Control module.

    2.

  2. This step determines if the failure condition is present.

    3.

  3. This step determines if the MAP sensor is the cause of the condition.

    4.

  4. This step determines if the 5-volt reference circuit is the cause of the condition. 4.8 volts is the minimum output that the gasoline Control Module should supply on the 5-volt reference circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

1

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

--

Go to Step 2

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

2

  1. Using the scan tool, establish communication with the gasoline Control Module (VCM/PCM or ECM).
  2. Observe the MAP Sensor data parameter.

Does the MAP sensor data parameter indicate MAP voltage less than the specified value?

0.2 V

Go to Step 5

Go to Step 3

3

  1. Using the scan tool, establish communication with the Alternative Fuels ECM.
  2. Observe the MAP Sensor data parameter.

Does the MAP sensor data parameter indicate MAP voltage less than the specified value?

0.09 V

Go to Step 13

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. Disconnect the MAP sensor connector.
  2. Jumper the 5-volt reference circuit terminal to the MAP signal circuit terminal using a fused jumper.
  3. Observe the MAP Sensor data parameter.

Does the MAP sensor data parameter indicate MAP voltage GREATER than the specified value?

4.8 V

Go to Step 11

Go to Step 6

6

  1. Remove the jumper.
  2. Connect the J 39200 DMM between the 5-volt reference circuit terminal and GROUND.
  3. Measure the voltage on the 5-volt reference circuit.

Is the voltage LESS than the value specified?

4.8 V

Go to Step 9

Go to Step 7

7
  1. Inspect the MAP sensor signal circuit for an open or high resistance between the sensor connector and the gasoline Control Module (VCM/PCM or ECM).
  2. Inspect for proper terminal contact at both the gasoline Control Module connector and the MAP sensor connector.
  3. Repair wiring or terminal contact as necessary.

Was a wiring or terminal repair necessary?

--

Go to Step 14

Go to Step 8

8
  1. Inspect the MAP sensor signal circuit for a short to engine ground or to the sensor ground circuit.
  2. Disconnect the Alternative Fuels ECM connector containing the MAP sensor signal circuit in order to determine if the ECM is the cause of the short.
  3. Repair wiring as necessary.

Was a wiring repair made?

--

Go to Step 14

Go to Step 12

9
  1. Inspect the 5-volt reference circuit for an open or high resistance condition between the sensor connector and the gasoline Control Module (VCM/PCM or ECM) connector terminal.
  2. Inspect for proper terminal contact at both the gasoline Control Module connector and the MAP sensor connector.
  3. Repair wiring or terminal contact as necessary.

Was a wiring or terminal repair necessary?

--

Go to Step 14

Go to Step 10

10
  1. Inspect all 5-volt reference circuits for a short to ground. Some 5-volt reference circuits are shared within the PCM. The short may be located on either of the 5-volt reference circuits that the PCM provides.
  2. Disconnect the Alternative Fuels ECM connector that contains the 5-volt reference circuit in order to determine if the Alternative Fuels ECM is the cause of the short.
  3. Disconnect the other sensors that are connected to the gasoline Control Module 5-volt reference circuits in order to determine if a sensor is the cause of the short.
  4. Repair wiring or replace components as necessary.

Was a repair made?

--

Go to Step 14

Go to Step 12

11

Replace the MAP Sensor. Refer to Manifold Absolute Pressure Sensor Replacement in the Engine Controls section of the G Van Service Manual.

Is the replacement complete?

--

Go to Step 14

--

12

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 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-over to gasoline operation is necessary. Remove the CNG 20-amp fuse in order to perform the switch-over.

  3. Perform the Crankshaft Position System Variation Learn .

Is the replacement complete?

--

Go to Step 14

--

13
  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.

Is the replacement complete?

--

Go to Step 14

--

14
  1. Using a scan tool, clear the DTC information from BOTH Control Modules.
  2. Operate the vehicle under the Conditions for Running the DTC.
  3. Using the scan tool parameter DTC STATUS, ensure that this DTC runs.

Did this DTC run and pass?

--

System OK

Go to Step 2