GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Kodiak C-Series (Crew) C6/C7/C8 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 Manifold Absolute Pressure Sensor Diagnosis

Circuit Description

The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold which gives an indication of the engine load. The MAP sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to the pressure changes in the manifold. With low MAP such as during idle or deceleration, the PCM should detect a low signal voltage. With high MAP such as ignition ON, with the engine OFF or wide-open throttle (WOT), the PCM should detect a high signal voltage. The MAP sensor is also used in order to calculate the barometric pressure (BARO) 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 PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 will set. If the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will set.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests the MAP sensors ability to correctly indicate BARO. BARO varies with altitude and atmospheric conditions.

Step

Action

Value(s)

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Inspect for the following conditions:
    2. • Vacuum hoses disconnected, damaged, or incorrectly routed
    • MAP sensor seal missing or damaged
    • Restrictions in the MAP sensor vacuum source
    • Intake manifold vacuum leaks
  2. Repair as necessary.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the MAP sensor pressure with a scan tool.

    3. Important: The vehicle used for a comparison is not limited to the same type of vehicle that is being serviced. A vehicle known to provide an accurate reading is acceptable.

  3. Compare these value to a value observed in a known good vehicle.

Is the difference between the two vehicles less than the specified value?

3 kPa

Go to Step 4

Go to Step 8

4
  1. Observe the MAP sensor pressure with a scan tool.
  2. Start the engine.

Does the MAP sensor pressure change?

--

Go to Step 5

Go to Step 8

5
  1. Turn OFF the ignition.
  2. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
  3. Connect a Mityvac to the MAP sensor.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the MAP sensor pressure with the scan tool.
  6. Apply vacuum to the MAP sensor with the MItyvac in 1 inch Hg increments. Each 1 inch Hg should decrease MAP sensor pressure by 3-4 kPa.

Is the decrease in MAP sensor pressure consistent?

--

Go to Step 6

Go to Step 18

6

Apply vacuum with the Mityvac until 20 inches Hg is reached.

Is the MAP sensor pressure less than the specified value?

34 kPa

Go to Step 7

Go to Step 8

7

Disconnect the Mityvac from the MAP sensor.

Does the MAP sensor pressure return to the value observed in step 3?

--

System OK

Go to Step 20

8
  1. Disconnect the MAP sensor electrical connector.
  2. Observe the MAP sensor voltage with the scan tool.

Is the voltage less than the specified value?

0.1 V

Go to Step 9

Go to Step 13

9

Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage more than the specified value?

5.2 V

Go to Step 14

Go to Step 10

10

Probe the 5-volt reference circuit of the MAP sensor with a test lamp that is connected to a good ground. Refer to Circuit Testing and Probing Electrical Connectors in Wiring Systems.

Is the test lamp OFF?

--

Go to Step 15

Go to Step 11

11
  1. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor.
  2. Observe the MAP sensor voltage with the scan tool.

Is the voltage more than the specified value?

4.9 V

Go to Step 12

Go to Step 16

12
  1. Remove the jumper wire.
  2. Probe the low reference circuit of the MAP sensor with a test lamp that is connected to battery voltage. Refer to Circuit Testing and Probing Electrical Connectors in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 18

Go to Step 17

13

Important: Disconnecting the PCM may eliminate the short during testing. The MAP sensor may be damaged if the circuit is shorted to a voltage source.

Test the MAP sensor signal circuit between the PCM and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 21

14

Important: Disconnecting the PCM may eliminate the short during testing. The MAP sensor may be damaged if the circuit is shorted to a voltage source.

Test the 5-volt reference circuit between the PCM and the MAP sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 21

15

Test the 5-volt reference circuit between the PCM and the MAP sensor for the following conditions:

    • A short to ground
    • An open
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 19

16

Test the MAP sensor signal circuit between the PCM and the MAP sensor for the following conditions:

    • A short to ground
    • An open
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 19

17

Test the low reference circuit between he PCM and the MAP sensor for high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 19

18

Test for an intermittent and for a poor connection at the MAP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 20

19

Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 22

Go to Step 21

20

Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement .

Did you complete the replacement?

--

Go to Step 22

--

21

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 22

--

22
  1. Clear any DTCs that may have set with the scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.

Did you correct the condition?

--

System OK

Go to Step 2