GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0069: Supercharger Inlet Pressure (SCIP) - Barometric Pressure (BARO) Correlation

Diagnostic Fault Information

SC Inlet Pressure

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

5-Volt Reference

P012C, P0641

P0069

P012C

P0641

P0069, P012B

SC Inlet Pressure Sensor Signal

P012B, P012C

P0069

P012C

P0120, P0641, P2229

P0069, P012B

Low Reference

--

P0069, P012B

P012B, P012D

--

P0069, P012B


BARO Sensor

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

5-Volt Reference Circuit

P0069, P0641, P2228

P0069

P0069, P2228

P0069, P0641, P2229

P2227

BARO Sensor Signal Circuit

P0069, P2228

P0069

P0069, P2228

P0069, P0641, P2224, P2229

P2227

Low Reference Circuit

--

P0069

P0069, P2229

--

P2227

Typical Scan Tool Data

SC Inlet Pressure Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON, engine OFF

Normal Parameter Range: BARO

5-Volt Reference

8-10 kPa

8-10 kPa

96-104 kPa

SC Inlet Pressure Sensor Signal

8-10 kPa

8-10 kPa

96-104 kPa

Low Reference

--

90-104 kPa

--


BARO Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition ON, engine OFF

Normal Range: BARO

5-Volt Reference Circuit

8-10 kPa

8-10 kPa

200-208 kPa

Sensor Signal Circuit

8-10 kPa

8-10 kPa

200-208 kPa

Low Reference Circuit

--

191 kPa

--

Circuit Description

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:

    • A ECM supplied and regulated 5-volt reference circuit
    • A ECM supplied ground for the low reference circuit
    • A sensor signal circuit that supplies a voltage input to the ECM

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 P0069 sets.

Conditions for Running the DTC

    • DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0128, P012B, P012C, P012D, P0220, P0502, P1516, P2101, P2227, P2228, P2229 are not set.
    • The ignition is ON.
        OR
    • The engine is running.
    • DTC P0069 runs continuously when the above conditions are met.

Conditions for Setting the DTC

    • The ECM detects that during ignition ON, with the engine OFF, the calculated difference between BARO and SCIAP, whether that value is negative or positive, is greater than 12 kPa for greater than 30 seconds.
        OR
    • The ECM has detected that a wide open throttle update event has occurred within the previous 2 kilometers (1.2 miles) and the difference between BARO, and a calculated BARO using the SCIAP sensor, is greater than 12 kPa for greater than 30 seconds.
        OR
    • The ECM has not detected a wide open throttle update event within the previous 2 kilometers (1.2 miles) and the difference between BARO, and a calculated BARO using the SCIAP sensor, is greater than 60 kPa for greater than 30 seconds.

Action Taken When the DTC Sets

DTC P0069 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0069 is a Type B DTC.

Diagnostic Aids

    • Any condition that can cause the BARO or SCIAP sensors to be shifted in value may cause this DTC to set.
    • A slight to moderate resistance of 20-50 ohms on the 5-volt reference terminal C or the low reference circuit terminal A may cause this DTC to set.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

    • J 23738-A Mityvac
    • J 35555 Metal Mityvac

Circuit/System Verification

  1. Verify that DTCs P0106, P0107, P0108, P012B, P012C, P012D, P0641, P0651, or P2227, P2228, P2229 are not set.
  2. If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

    Important: 

       • 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.

  3. 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.
  4. Ignition ON, observe the scan tool SC Inlet Pressure Sensor kPa parameter. Start the engine. The SC Inlet Pressure Sensor parameter should decrease.
  5. 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.

Circuit/System Testing

  1. Verify the integrity of the SCIAP and BARO sensors by inspecting for the following conditions:
  2. • Damaged components
    • Loose or improper installation
    • An air flow restriction
    • A cracked or restricted SCIAP sensor vacuum hose
    • An intake manifold leak
  3. 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.
  4. Ignition OFF, disconnect the harness connector at the affected sensor.
  5. Ignition OFF, for 90 seconds test for less than 5 ohms between the low reference circuit terminal A and ground.
  6. 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.
  7. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C and ground.
  8. 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.
  9. Verify the scan tool sensor parameter is less than 12 kPa.
  10. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  11. 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.
  12. If less than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  13. If all circuits test normal, test or replace the affected sensor.

Component Test

Important: 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 MAP 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.
  4. THEN

  5. Using the J 23738-A or the J 35555 to apply 5 in Hg of vacuum to the MAP sensor, the parameter in the first column should decrease by 17 kPa. The acceptable range is indicated in the second column.
  6. Using the J 23738-A or the J 35555 to apply 10 in Hg of vacuum to the MAP sensor, the parameter in the first column should decrease by 34 kPa. The acceptable range is indicated in the third column.

Ignition ON, Engine OFF, MAP Sensor Parameter

MAP Sensor Parameter With 5 Inches of Vacuum Applied

MAP Sensor Parameter With 10 Inches of Vacuum Applied

100 kPa

79-87 kPa

62-70 kPa

95 kPa

74-82 kPa

57-65 kPa

90 kPa

69-77 kPa

52-60 kPa

80 kPa

59-67 kPa

42-50 kPa

70 kPa

49-57 kPa

32-40 kPa

60 kPa

39-47 kPa

22-30 kPa

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 J 23738-A or the J 35555 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.
  7. If the voltage is not within the specified range or is erratic, replace the affected sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Supercharger Air Inlet Pressure Sensor Replacement
    •  Barometric Pressure Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming