The supercharger inlet absolute pressure (SCIAP) sensor measures the pressure after the throttle body, but before the supercharger. Pressure in this area is affected by engine speed, throttle opening, air temperature, and barometric pressure (BARO). A diaphragm within the SCIAP 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 SCIAP 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 SCIAP sensor provides a signal voltage to the ECM, relative to the pressure changes, on the SCIAP 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 supercharge 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. The lowest manifold pressures occur when the vehicle is idling or decelerating. The SCIAP can range from 20-30 kPa, when pressures are low, to as much as BARO when pressures are high. The ECM monitors the SCIAP sensor signal for pressure outside of the normal range.

P012C

P012D

P012C

The ECM detects that the SCIAP sensor voltage is less than 0.10 volt for greater than 5 seconds.

P012D

The ECM detects that the SCIAP sensor voltage is more than 4.80 volts for greater than 5 seconds.

DTCs P012C and P012D are Type B DTCs.

DTCs P012C and P012D are Type B DTCs.

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 P0641 or P0651 are not set.

⇒	If any of the DTCs are set, refer to DTC P0641 or P0651.

2. Ignition ON, observe the scan tool SC Inlet Pressure Sensor parameter. The reading should be BARO. Refer to Altitude Versus Barometric Pressure.
3. Engine running at idle, observe the scan tool SC Inlet Pressure Sensor parameter. The reading should closely match the MAP Sensor parameter value.
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/Failure Records data.

Note: You must perform the Circuit/System Verification before proceeding with the Circuit/System Testing.

1. Verify the integrity of the SCIAP sensor system by inspecting for the following conditions:

•	Any damage to the SCIAP sensor housing

•	A loose or improperly installed SCIAP sensor

•	A restriction in the vacuum source of the SCIAP sensor

2. Ignition OFF, disconnect the harness connector at the SCIAP sensor.
3. Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit and ground.

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

4. 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.

5. Verify the scan tool SC Inlet Pressure Sensor parameter is less than 20 kPa.

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

6. Install a 3A fused jumper wire between the 5-volt reference circuit terminal C and the signal circuit terminal B. Verify the scan tool parameter is greater than 95 kPa.

⇒	If less than the specified parameter, test the signal circuit for a short to ground, open/high resistance. If the circuit tests normal, replace the ECM.

7. If all circuits test normal, test or replace the SCIAP sensor.

Note: You must perform the Circuit System Testing before proceeding with the Component Testing.

1. Ignition OFF, remove the SCIAP sensor.
2. Install a 3A fused jumper wire between the 5-volt reference terminal C of the sensor and 5-volt reference.
3. Install a jumper wire between the low reference terminal A of the sensor and ground.
4. Install a jumper wire at the signal 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 J 35555 Metal Mityvac slowly apply vacuum to the sensor while monitoring the voltage on the DMM. The voltage should vary between 4.9-0.04 volts, without any spikes or dropouts.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.