P012B
DTC P012B
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 Descriptor
DTC P012B
- Supercharger Inlet Pressure Sensor Performance
Circuit/System Description
The supercharger inlet pressure sensor measures the pressure between the throttle body and the supercharger. Pressure in this area is affected by engine speed, throttle opening, air temperature, and barometric pressure (BARO). The sensor provides a signal voltage that varies relative to pressure changes that occur from the various load and operating conditions of the engine. The engine control module (ECM) supplies a regulated 5 V reference circuit, and monitors the signal circuit.
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 supercharger inlet pressure can range from 20 kPa to as high as BARO.
The intake airflow system performance diagnostic provides the within-range rationality check for the mass air flow (MAF), supercharger inlet pressure, manifold absolute pressure (MAP) and the throttle position (TP) sensors. This is an explicit model-based diagnostic containing multiple models for the intake system. These models include the MAF Performance Test, MAP Performance Test 1, MAP Performance Test 2 and TP Performance Test, which are displayed on the scan tool.
The estimates of MAF, supercharger inlet pressure and throttle position from the system of models and calculations are compared to the actual measured values from the MAF, supercharger inlet pressure and the throttle position sensors to determine the appropriate DTC to fail.
Conditions for Running the DTC
* DTC P0096, P0097, P0098, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0128, P012C, P012D, P0335, P0336, P2227, P2228, or P2229 is not set.
* The engine speed is between 450-6,200 rpm.
* The engine coolant temperature (ECT) is between -20 to +125°C (-4 to +257°F).
* The intake air temperature (IAT) is between -7 to +125°C (+19 to +257°F).
* The DTC runs continuously when the above conditions are met.
Conditions for Setting the DTC
The ECM detects the supercharger inlet pressure sensor is stuck within range for greater than 1 s.
Action Taken When the DTC Sets
DTC P012B is a Type B DTC.
Conditions for Clearing the MIL/DTC
DTC P012B is a Type B DTC.
Diagnostic Aids
* The harness connectors for the BARO sensor and the supercharger inlet pressure sensor are of the same configuration but are not interchangeable. Review the engine controls schematics for the BARO sensor and the supercharger inlet pressure sensor and note the circuit colors. Inspect the wiring harnesses of both sensors for the proper connections.
* This DTC may set due to any of the following conditions:
- Any condition that can cause the MAF, MAP, supercharger inlet pressure, and throttle position sensors to be shifted in value
- A resistance of 10-20 ohms on the 5 V reference or low reference circuits of the supercharger inlet pressure sensor
- Any condition that may cause the supercharger by-pass valve to bind or stick in either the open or closed positions
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
Description and Operation Reference
* Boost Control System Diagnosis
* Supercharger Description and Operation
* Boost Control System Description
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
Special Tools
J 23738-A - Mityvac
Circuit/System Verification
1. If you were sent here from DTC P0101, P0106, P0121 or P1101, refer to Circuit/System Testing.
2. Verify DTC P006D, P012C, P012D, P0641, P2227, P2228, or P2229 is not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
3. Ignition ON.
4. Verify the scan tool TB Idle Airflow Compensation parameter is less than 90 %.
• If 90 % or greater
Refer to Throttle Body Cleaning Procedures.
• If less than 90 %
Note: If the Throttle Sweep Test is not available on the scan tool, observe the scan tool TP Sensor 1 and 2 Agree/Disagree parameter while performing the following tests:
* Slowly depress the accelerator pedal to wide open throttle (WOT) and then slowly return the pedal to closed throttle. Repeat the procedure several times.
* Rapidly depress the accelerator pedal from the rest position to WOT and release pedal. Repeat the procedure several times.
5. Verify the scan tool TP Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.
• If Disagree
Refer to DTC P0120-P0123, P0220, P0222, P0223, or P2135 (Without Supercharger) P0120DTC P0120-P0123, P0220, P0222, P0223, or P2135 (Supercharger) for further diagnosis.
• If Agree
6. Determine the current vehicle testing altitude.
7. Verify the scan tool MAP Sensor pressure parameter is within the range specified in the Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure table.
• The MAP Sensor pressure is not in range
Refer to DTC P0106 (Without Supercharger) P0106DTC P0106 (Supercharger) for further diagnosis.
• The MAP Sensor pressure is within range
8. Verify the scan tool SC Inlet Pressure Sensor pressure parameter is within range specified in the Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure table.
• The SC Inlet Pressure Sensor pressure is not in range
Refer to Circuit/System Testing.
• The SC Inlet Pressure Sensor pressure is within range
9. Verify the SC Inlet Pressure Sensor pressure parameter decreases after starting the engine.
• The SC Inlet Pressure Sensor pressure did not decrease
Refer to Circuit/System Testing.
• The SC Inlet Pressure Sensor pressure decreases
10. Verify the scan tool MAP Sensor pressure parameter is between 26-52 kPa (3.8-7.5 psi) and changes with accelerator pedal input.
• If not between 26-52 kPa (3.8-7.5 psi) or does not change
Refer to DTC P0106 (Without Supercharger) P0106DTC P0106 (Supercharger) for further diagnosis.
• If between 26-52 kPa (3.8-7.5 psi) and changes
11. Verify the scan tool MAF Sensor g/s parameter changes smoothly and gradually as the engine speed is increased and decreased while performing the actions listed below.
1. Engine idling
2. Perform the scan tool snapshot function.
3. Increase the engine speed slowly to 3,000 RPM and then back to idle.
4. Exit from the scan tool snapshot and review the data.
5. Observe the MAF Sensor parameter frame by frame with a scan tool.
• The MAF Sensor parameter does not change smoothly and gradually
Refer to DTC P0101 (Without Supercharger) P0101DTC P0101 (Supercharger) for further diagnosis.
• The MAF Sensor parameter changes smoothly and gradually
12. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
13. Verify a DTC does not set.
• If any DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
• If no DTCs set
14. All OK
Circuit/System Testing
Note: You must perform Circuit/System Verification before proceeding with the Circuit/System Testing.
1. Verify none of the following conditions exist:
* Loose clamps, cracks, or other damage in the air intake duct system
* Collapsed or restricted air intake duct system
* Restricted air filter
* Splits, kinks or improper connections at the vacuum hoses
* Missing, restricted or leaking exhaust components-Refer to Symptoms - Engine Mechanical Symptoms - Engine Mechanical.
* Vacuum leaks at the intake manifold and throttle body
• If a condition exists, repair as necessary.
• If no condition exists.
2. Verify the integrity of the supercharger system by inspecting for the following conditions:
* A binding or restricted supercharger bypass valve, linkage or actuator. Refer to Supercharger Cleaning and Inspection
* Any damaged components
* Loose or improper installation of any components
* An air flow restriction
* Any vacuum leaks
* Water intrusion
* In cold climates, inspect for any snow or ice buildup
* Contamination or debris blocking or restricting the supercharger inlet pressure sensor inlet port
• If a condition exists, repair as necessary.
• If no condition exists.
3. Test or replace the supercharger inlet pressure sensor.
Component Testing
Note: You must perform the Circuit/System Testing before proceeding with the Component Testing.
1. Ignition OFF, remove the supercharger inlet pressure sensor.
2. Install a 3 A fused jumper wire between the 5 V reference terminal 1 of the sensor and 5 V. Install a jumper wire between the low reference terminal 2 of the sensor and ground.
3. Test for 4.9-0.4 V without any spikes or dropouts between the signal terminal 3 and the low reference terminal 2 while slowly applying vacuum to the sensor with the J 23738-A - Mityvac.
• If not between 4.9-0.4 V or has spikes or dropouts
Replace the supercharger inlet pressure sensor.
• If between 4.9-0.4 V and there are no spikes or dropouts
4. All OK
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic repair.
* Supercharger Air Inlet Pressure Sensor Replacement (LS9)
* Control Module References Control Module References for ECM replacement, programming, and setup