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P0108




DTC P0107 or P0108 (Without Supercharger)

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0107
- Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage

DTC P0108
- Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage

Diagnostic Fault Information






Typical Scan Tool Data






Circuit Description

The manifold absolute pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by engine speed, throttle opening, air temperature, and barometric pressure (BARO). A diaphragm within the MAP sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance. The MAP sensor wiring includes 3 circuits. The engine control module (ECM) supplies a regulated 5 volts to the sensor on a 5-volt reference circuit. The ECM supplies a ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to the pressure changes, on the MAP sensor signal circuit. The ECM converts the signal voltage input to a pressure value.

Under normal operation the highest pressure that can exist in the intake manifold is equal to BARO. This occurs when the vehicle is operated at wide-open throttle (WOT) or when the ignition is ON while the engine is OFF. Under these conditions, the ECM uses the MAP sensor to determine the current BARO. The lowest manifold pressures occur when the vehicle is idling or decelerating. The ECM monitors the MAP sensor signal for pressure outside of the sensor operating range.

Conditions for Running the DTC

P0107

This DTC runs continuously.

P0108

This DTC runs continuously.

Conditions for Setting the DTC

P0107

The ECM detects that the MAP sensor voltage is less than 0.1 volt for more than 4 seconds.

P0108

The ECM detects that the MAP sensor voltage is more than 4.9 volts for greater than 4 seconds.

Action Taken When the DTC Sets

DTCs P0107 and P0108 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0107 and P0108 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics (LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LS7) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views 5 Bow Lowered Switch (CM7)

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Verification

1. Verify that DTC P0641, or P0651 is not set.

• If the DTC is set
Refer to DTC P0641 or P0651 (ECM With Supercharger) DTC P0641 or P0651 (ECM Without Supercharger) for further diagnosis.

• If the DTC is not set

2. Engine Idling.

3. Verify the scan tool MAP voltage parameter is between 0.3-4.8 V and changes with accelerator pedal input.

• If not between 0.3-4.8 V or does not change
Refer to Circuit/System Testing - step 1.

• If between 0.3-4.8 V and changes

4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records data.

5. Verify the DTC does not set.

• If the DTC sets
Refer to Circuit/System Testing - step 1.

• If the DTC does not set

6. All OK.

Circuit/System Testing

1. Ignition OFF, and all vehicle systems OFF, disconnect the harness connector at the B74 manifold absolute pressure sensor. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 2 ohms between the low reference circuit terminal A or 2 and ground.

• If 2 ohms or greater

1. Ignition OFF, disconnect the X2 harness connector at the K20 engine control module.

2. Test for less than 2 ohms in the low reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 engine control module.

• If less than 2 ohms

3. Ignition ON.

4. Test for 4.8-5.2 V between the 5 V reference circuit terminal C or 1 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the X2 harness connector at the K20 engine control module.

2. Test for infinite resistance between the 5 V reference circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the 5 V reference circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K20 engine control module.

Note: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.

• If greater than 5.2 V

1. Ignition OFF, disconnect the X2 harness connector at the K20 engine control module, ignition ON.

2. Test for less than 1 V between the 5 V reference circuit and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 engine control module.

• If between 4.8-5.2 V

5. Verify the scan tool MAP voltage parameter is less than 0.2 V.

• If 0.2 V or greater

1. Ignition OFF, disconnect the X2 harness connector at the K20 engine control module, ignition ON.

2. Test for less than 1 V between the signal circuit terminal B or 3 and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K20 engine control module.

• If less than 0.2 V

6. Install a 3 A fused jumper wire between the signal circuit terminal B or 3 and the 5 V reference circuit terminal C or 1.

7. Verify the scan tool MAP voltage parameter is greater than 4.5 V.

• If 4.5 V or less

1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the K20 engine control module.

2. Test for infinite resistance between the signal circuit terminal B or 3 and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the signal circuit end to end.

• If 2 ohms or greater, repair the open or high resistance in the circuit.

• If less than 2 ohms, replace the K20 engine control module.

• If greater than 4.5 V

8. Test or replace the B74 manifold absolute pressure sensor.

Component Testing

Note: You must perform the Circuit/System Testing in order to verify the integrity of the MAP sensor circuits before proceeding with the Component Testing.

Skewed Sensor Test

1. Using the following steps and referencing the table below will determine if the B74 manifold absolute pressure sensor is skewed.

2. Ignition ON, engine OFF, observe the MAP Sensor scan tool parameter.

3. Use the observed MAP Sensor Scan Tool parameter that is closest to a value that is indicated in the first column.
THEN

4. Using the J-23738-A - Vacuum Pump to apply 5 in Hg of vacuum to the B74 manifold absolute pressure sensor, the parameter in the first column should decrease by 17 kPa (2.5 psi). The acceptable range is indicated in the second column.

• If not within the acceptable range
Replace the B74 manifold absolute pressure sensor.

• If within the acceptable range

5. Using the J-23738-A - Vacuum Pump to apply 10 in Hg of vacuum to the B74 manifold absolute pressure sensor, the parameter in the first column should decrease by 34 kPa (5.0 psi). The acceptable range is indicated in the third column.

• If not within the acceptable range
Replace the B74 manifold absolute pressure sensor.

• If within the acceptable range

6. All OK.





Erratic Signal Test

1. Ignition OFF, remove the B74 manifold absolute pressure sensor.

2. Install a 3A fused jumper wire between the 5 V reference circuit terminal C or 1 and the corresponding terminal of the B74 manifold absolute pressure sensor.

3. Install a jumper wire between the low reference terminal A or 2 of the B74 manifold absolute pressure sensor and ground.

4. Install a jumper wire at terminal B or 3 of the B74 manifold absolute pressure sensor.

5. Connect a DMM between the jumper wire from the terminal B or 3 of the B74 manifold absolute pressure sensor and ground.

6. Ignition ON, with the J-23738-A - Vacuum Pump, slowly apply vacuum to the sensor while observing the voltage on the DMM. The voltage should vary between 4.9-0.2 V without any spikes or dropouts.

• If not between 4.9-0.2 V or has spikes or dropouts
Replace the B74 manifold absolute pressure sensor.

• If between 4.9-0.2 V and there are no spikes or dropouts

7. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Manifold Absolute Pressure Sensor Replacement (Without LS9) Service and Repair

* Control Module References Control Module References for ECM replacement, programming, and setup

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