The barometric pressure (BARO) sensor measures the pressure of the atmosphere. This pressure is affected by altitude and weather conditions. A diaphragm within the BARO sensor is displaced by the pressure changes that occur from varying altitudes and weather conditions. The sensor translates this diaphragm action into the voltage signal input that is used by the engine control module (ECM) for diagnostics and emissions control.

The supercharger inlet absolute pressure (SCIAP) sensor measures the absolute pressure of the air just after the throttle body, at the inlet of the supercharger. The plenum volume between the throttle body (TB) and the supercharger is where this sensor is located, and for the purpose of this diagnostic, this area is considered to be the intake manifold. The diaphragm within the SCIAP sensor functions in the same manner as the BARO sensor. The sensors are not interchangeable.

The purpose of this diagnostic is to analyze the correlation between the BARO sensor, and the SCIAP sensor. This is accomplished by continually comparing the difference between BARO and SCIAP at key ON, engine OFF (KOEO), at closed throttle idle conditions, and at wide open throttle update events. At KOEO the difference between BARO and SCIAP is represented on the scan tool by the SC Inlet Pressure parameter as a value that should be very close to zero. A negative SC Inlet Pressure parameter means that the BARO sensor value is less than the SCIAP value. A positive SC Inlet Pressure parameter represents a BARO sensor value that is more than the SCIAP value.

At idle the SC Inlet Pressure parameter represents the calculated difference between BARO and the reduced pressure that is present in the supercharger intake plenum as a positive value. At wide open throttle the SC Inlet Pressure parameter represents the calculated difference between BARO and the increased pressure that is present in the supercharger intake plenum, and should be very close to zero.

Both sensors have the following types of circuits:

Changes in BARO due to weather are relatively small, while changes due to altitude are significant. Pressure can range from 56 kPa at an altitude of 4267 meters (14,000 feet), to 104 kPa at or below sea level.

If the ECM detects that the BARO sensor signal and the SCIAP sensor signal are not within a calibrated range of each other, whether that value is negative or positive, DTC P006D sets.

DTC P006D is a Type B DTC.

DTC P006D is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

1. Verify that DTCs P0106, P0107, P0108, P012B, P012C, P012D, P0641, P0651, or P2227, P2228, P2229 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

Note: 

•	The harness connectors for the following sensors are the same configuration but are not interchangeable.

•	Review the engine controls schematics for the BARO sensor and for the SCIAP sensor and note the circuit colors.

•	Inspect the wiring harness of the BARO sensor for the proper connections.

•	Inspect the wiring harness of the SCIAP sensor for the proper connections.

2. Ignition ON, engine OFF, determine the altitude for your area. Refer to Altitude Versus Barometric Pressure. Observe the SC Inlet Pressure Sensor and BARO Sensor parameters. The readings should be within 5 kPa of each other and the Altitude Versus Barometric Pressure table.
3. Ignition ON, observe the scan tool SC Inlet Pressure Sensor kPa parameter. Start the engine. The SC Inlet Pressure Sensor parameter should decrease.
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 from the Freeze Frame Records data.

1. Verify the integrity of the SCIAP and BARO sensors by inspecting for the following conditions:

•	Damaged components

•	Loose or improper installation

•	An air flow restriction

•	A cracked or restricted SCIAP sensor vacuum hose

•	An intake manifold leak

2. Ignition ON, determine which sensor is out of range by comparing SC Inlet Pressure and BARO Sensor kPa parameters with a scan tool. Compare those values to the Altitude Versus Barometric Pressure table.
3. Ignition OFF, disconnect the harness connector at the affected sensor.
4. Ignition OFF, for 90 seconds test for less than 5 ohms between the low reference circuit terminal A and ground.

⇒	If greater than the specified range, test the low reference circuit terminal A or an open/high resistance. If the circuit tests normal, replace the ECM.

5. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

6. Verify the scan tool sensor parameter is less than 12 kPa.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

7. Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal C. Verify the scan tool sensor parameter is greater than 95 kPa for the SCIAP sensor, or 199 kPa for the BARO sensor.

⇒	If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

8. If all circuits test normal, test or replace the affected sensor.

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

Skewed Signal Test

1. Using the following steps and referencing the table below will determine if the BARO or SCIAP sensor is skewed.
2. Ignition ON, engine OFF, observe the BARO and SC inlet pressure sensor scan tool parameters.
3. Use the observed BARO or SC Inlet Pressure Sensor scan tool parameter that is closest to a value that is indicated in the first column.

THEN

4. Using the J23738-A Mityvac or the J 35555 Metal Mityvac to apply 5 in Hg of vacuum to the affected sensor, the parameter in the first column should decrease by 17 kPa. The acceptable range is indicated in the second column.
5. Using the J23738-A Mityvac or the J 35555 Metal Mityvac to apply 10 in Hg of vacuum to the affected sensor, the parameter in the first column should decrease by 34 kPa. The acceptable range is indicated in the third column.

Erratic Signal Test

1. Ignition OFF, remove the sensor.
2. Install a 3A fused jumper wire between the 5-volt reference circuit terminal C and the corresponding terminal of the sensor.
3. Install a jumper wire between the low reference circuit terminal A of the sensor and ground.
4. Install a jumper wire at the terminal B of the sensor.
5. Connect a DMM between the jumper wire from terminal B of the sensor and ground.
6. Ignition ON, with the J23738-A Mityvac or the J 35555 Metal Mityvac slowly apply vacuum to the sensor while monitoring the voltage on the DMM. The voltage should vary between 0-5.2 volts, without any spikes or dropouts.

⇒	If the voltage is not within the specified range or is erratic, replace the affected sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.