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.

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

5-Volt Reference

P0107, P0405, P0452, P0462, P0532, P0641, P1107

P0107

P0107, P1107

P0641

P0107

MAP Sensor Signal

P0107, P1107

P0107, P1107

P0107

P0108, P1106

P0107

Low Reference

--

P0108

P0108, P1106

--

P0108

Typical Scan Tool Data

MAP Sensor

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

5-Volt Reference

--

10 kPa

10 kPa

104 kPa

MAP Sensor Signal

12-103 kPa

10 kPa

10 kPa

104 kPa

Low Reference

--

--

90 kPa

--

Circuit/System Description

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits:

    • 5-volt reference circuit
    • Low reference circuit
    • MAP sensor signal circuit

The control module supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The control module also provides a ground on the low reference circuit. The MAP sensor provides a signal to the control module on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The control module should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The control module should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a wide open throttle (WOT). The MAP sensor is also used in order to determine the barometric pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The control module monitors the MAP sensor signal for voltage outside of the normal range.

Diagnostic Aids

Poor idle characteristics may be due to uncontrolled fueling caused by an open or high resistance in the heated oxygen sensor (HO2S) 1 low signal circuit. Before replacing any component, ensure that this condition does not exist.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Scan Tool Data List

Special Tools Required

J 23738-A Mityvac

Circuit/System Testing

Perform the Diagnostic System Check - Vehicle .

  1. Start the engine.
  2. Monitor the DTC information with the scan tool.
  3. If DTC P0641 or P0651 is also set then correct DTC P0641 or P0651 first.
  4. Inspect for the following conditions:
  5. • Disconnected, damaged, or incorrectly routed vacuum hoses
    • MAP sensor disconnected from the vacuum source
    • Restrictions in the MAP sensor vacuum source
    • Intake manifold vacuum leaks
    • Inspect for a properly functioning oxygen sensor.
  6. With the ignition ON, and the engine OFF.
  7. Disconnect the MAP sensor.
  8. Measure for 4.8-5.2 volts from the 5-volt reference circuit of the MAP sensor to a good ground, with a DMM.
  9. • If more than 5.2 volts, then test the circuit for a short to voltage. If the circuit tests normal, replace the control module.
    • If less than 4.8 volts, then test the circuit for high resistance, an open, a short to ground, or an intermittent and poor connection or at the control module. If the circuit tests normal, replace the control module.
  10. Use a scan tool and observe the MAP sensor for less than 12 kPa.
  11. If the MAP sensor is more than 12 kPa then test the MAP sensor signal circuit for a short to voltage. If the circuit tests normal, replace the control module.
  12. Use a 3-amp fused jumper wire and connect it between the MAP sensor 5-volt reference circuit and the MAP sensor signal circuit.
  13. Use a scan tool and observe the MAP sensor for more than 103 kPa.
  14. If the MAP sensor is less than 103 kPa, then test the MAP sensor signal circuit for a short to ground, an open, high resistance. If the circuit tests normal, replace the control module.
  15. Turn OFF the ignition and allow the control module to power down.
  16. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
  17. Connect a J 23738-A to the MAP sensor.
  18. Turn ON the ignition, with the engine OFF.
  19. Observe the MAP sensor pressure with the scan tool.
  20. Apply vacuum to the MAP sensor with the J 23738-A in 1 inch Hg increments until 15 inches Hg is reached. Each 1 inch Hg should decrease MAP sensor pressure by 3-4 kPa. Monitor the MAP sensor pressure to see if the decrease in pressure is consistent.
  21. If decrease in pressure is not consistent then, test for intermittent and poor connections at the MAP sensor. If connections test OK, replace the MAP sensor
  22. Apply vacuum with the J 23738-A until 20 inches Hg is reached. Observe the MAP sensor pressure for less than 34 kPa.
  23. If more than 34 kPa, test for an intermittent and for a poor connection at the MAP sensor. If connections test OK, replace the MAP sensor.
  24. With a DMM measure for less than 5 ohms of resistance between the low reference circuit of the MAP sensor and battery negative post.
  25. If the resistance is more than 5 ohms, then test the low reference circuit for a high resistance. If the circuit tests normal, replace the control module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Manifold Absolute Pressure Sensor Replacement
    •  Control Module References