Important: The following applies to the intake airflow system performance diagnostic that is used in this supercharged engine:

The intake airflow system performance diagnostic provides the within-range rationality check for the mass air flow (MAF), supercharger inlet absolute pressure (SCIAP), MAP, by-pass valve stuck, and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing 4 separate models for the intake system.

The estimates of MAF, SCIAP, and TP that are obtained from this system of models and calculations are then compared to the actual measured values from the MAF, SCIAP, and the TP sensors and to each other to determine the appropriate DTC to fail. The following table illustrates the possible failure combinations and the resulting DTC or DTCs.

The engine control module (ECM) detects that the actual measured airflow from the MAF, MAP, SC Inlet Pressure and TP sensors is not within a range of the calculated airflow that is derived from the system of models by greater than a calibrated threshold, for greater than 10 seconds.

DTC P012B is a Type B DTC.

DTC P012B is a Type B DTC.

This DTC may set due to any of the following conditions:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Description and Operation 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 DTCs P0102, P0103, P0106, P0107, P0108, P0121, P0641, P0651, P2228, or P2229 are not set.

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

2. Ignition ON, observe the MAP and SC Inlet Pressure Sensor kPa parameters with a scan tool. Start the engine and let it idle. The MAP Sensor and SC Inlet Pressure Sensor kPa parameters should decrease and closely match each other.

⇒	If the MAP Sensor parameter does not decrease and closely match the SC Inlet parameter, refer to DTC P0106 .

3. Ignition ON, depress the accelerator pedal completely to wide open throttle (WOT) and observe the TP Indicated Angle parameter with a scan tool. The TP Indicated Angle parameter should read 98-100 percent.

⇒	If the TP Indicated Angle parameter is not within the specified range, refer to DTC P1516, P2101, P2119, or P2176 .

4. Ignition ON, perform a snapshot of the throttle actuator control (TAC) data while performing the following actions. Refer to Scan Tool Snapshot Procedure .

4.1.	Slowly depress the accelerator pedal to WOT and then slowly release the pedal. Exit from the snapshot and review the data.

4.2.	Compare the TP Sensor 1 and the TP Sensor 2 parameters, frame by frame. The difference between the parameters should be less than 4 percent.

⇒	If the difference is greater than 4 percent, refer to DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135 .

5. Road test the vehicle and perform a brief wide open throttle (WOT) acceleration from 30 mph. The MAP sensor parameter on the scan tool should increase rapidly. This increase should be from approximately 35 kPa at idle to greater than 135 kPa.

⇒	If less than the specified range, refer to Boost Control System Diagnosis .

6. A skewed or stuck ECT, BARO, MAP, MAF/IAT, or IAT sensor 2 will cause the calculated models to be inaccurate and may cause this DTC to run when it should not. Refer to Temperature Versus Resistance and Altitude Versus Barometric Pressure .
7. Operate the vehicle within the Conditions for Running the DTC to verify that the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Important: 

1. Visually and physically inspect the integrity of the entire supercharger air induction system, for any of the following conditions:

•	A restricted or collapsed air intake duct

•	A misaligned or damaged air intake duct

•	A dirty or deteriorating air filter element

•	Any objects blocking the air inlet probe of the MAF/IAT sensor

•	Any contamination or debris on the sensing elements in the probe of the MAF/IAT sensor

•	Any water intrusion in the induction system

•	Any vacuum leak downstream of the MAF/IAT sensor

•	An intake manifold leak

⇒	If a condition is found, repair as necessary.

2. Visually and physically inspect all vacuum lines for cracking, loose fit, restrictions and proper routing at the following locations:

•	The SCIAP sensor

•	The MAP sensor

•	The by-pass valve solenoid

•	The by-pass valve actuator

⇒	If a condition is found, repair as necessary.

3. Visually and physically inspect the by-pass valve and cable for any of the following conditions:

•	A binding or sticking in the open or closed position

•	A binding when opening or closing

•	An incorrectly adjusted cable

•	Any damage

⇒	If any of the above conditions are found, refer to Supercharger Cleaning and Inspection .

4. Ignition OFF, disconnect the harness connector at the SCIAP sensor.
5. 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 for an open/high resistance. If the circuit tests normal, replace the ECM.

6. Verify the scan tool SC Inlet Pressure Sensor parameter is less than 20 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 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 range, test the signal circuit for a short to ground, open/high resistance. If the circuit tests normal, replace the ECM.

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

Important: 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 a 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 SCIAP sensor.
5. Connect a DMM between the jumper wire from terminal B of the SCIAP sensor and ground.
6. Ignition ON, with the J 23738-A or J 35555 slowly apply vacuum to the sensor while monitoring the voltage on the DMM. The voltage should vary between 4.9-0.4 volts, without any spikes or dropouts.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.