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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Bonneville 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Manifold Absolute Pressure Sensor Circuit Diagnosis

Object Number: 573630 Size: SF
Engine Controls Components
Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The manifold absolute pressure (MAP) sensor responds to changes in intake manifold vacuum. The MAP sensor signal voltage to the PCM varies from below 2.0 volts at idle to above 4.0 volts with the key on and the engine not running, or the engine running at wide open throttle (WOT).

The MAP sensor is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run in order to determine the engine vacuum level for other diagnostics, and to determine barometric pressure (BARO). The PCM monitors the MAP signals for voltages outside the normal range of the MAP sensor. If the PCM detects a MAP signal voltage that is excessively high, DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage sets. If the PCM detects a MAP signal voltage that is excessively low, DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage sets.

The PCM also uses the MAP sensor for throttle position (TP) sensor performance. If the PCM detects a TP in an out of range condition when the MAP reading is above or below a calibrated amount, DTC P0121 Throttle Position (TP) Sensor Performance sets.

Diagnostic Aids

Check for the following conditions:

    •  Monitor the MAP sensor using the scan tool. If the MAP sensor does not respond to throttle changes, check the 3X reference circuits from the ignition control module (ICM) to the PCM.
         If the 3X reference signal is lost, the PCM will only update the MAP sensor reading once per key cycle when the engine is first started.
         Depending on where the MAP sensor voltage is when the engine is started, the high or low voltage MAP sensor DTCs will set.
    • A faulty connection at PCM--Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Refer to Testing for Intermittent Conditions and Poor Connections and to Wiring Repairs in Wiring Systems.
    • Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display indicates the location of the fault. Refer to Wiring Repairs in Wiring Systems.
    •  Inspect for kinked and damaged vacuum hoses. Ensure that a good vacuum source is available. Refer to Emission Hose Routing Diagram .

Step

Action

Values

Yes

No

1

Was the Powertrain On Board Diagnostic System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Check for the following conditions:
    2. • A missing or damaged MAP sensor seal
    • Any disconnected, damaged, incorrectly routed vacuum hoses
    • Any intake manifold vacuum leaks
    • Any vacuum leaks at the throttle body
    • Any vacuum leaks at the EGR valve flange and the pipes
    • A faulty, missing, or incorrectly installed positive crankcase ventilation valve
  2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 14

Go to Step 3

3
  1. Disconnect the MAP sensor electrical connector.
  2. Observe the MAP voltage displayed on the scan tool.

Is the voltage equal to the specified value?

0 V

Go to Step 4

Go to Step 12

4
  1. Connect a test lamp between B+ and the MAP sensor signal circuit at the MAP sensor harness connector.
  2. Observe the MAP voltage displayed on the scan tool.

Does the voltage equal the specified value?

4.95 V

Go to Step 5

Go to Step 8

5
  1. Jumper the 5 volt reference A circuit and the MAP signal circuit together at the MAP sensor harness connector.
  2. Observe the MAP voltage displayed on the scan tool.

Does voltage equal the specified value?

4.95 V

Go to Step 6

Go to Step 7

6
  1. Turn the ignition off.
  2. Disconnect the PCM and check the sensor ground circuit for a high resistance, an open between the PCM and the MAP sensor, and for a faulty connection at the PCM.
  3. If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems .

Was a problem found?

--

Go to Step 14

Go to Step 10

7
  1. Check the 5 volt reference A circuit for a high resistance, an open between the PCM and the MAP sensor, and for a faulty connection at the PCM.
  2. If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Was a problem found?

--

Go to Step 14

Go to Step 9

8
  1. Turn the ignition off.
  2. Disconnect the PCM, and check the MAP sensor signal circuit for a high resistance, an open, a short to ground, or a short to the sensor ground circuit.
  3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 14

Go to Step 9

9
  1. Check the MAP sensor signal circuit for a faulty connection at the PCM
  2. If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems .

Did the terminal require replacement?

--

Go to Step 14

Go to Step 13

10
  1. Check for a faulty connection at the MAP sensor.
  2. If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems .

Was a problem found?

--

Go to Step 14

Go to Step 11

11

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

Did you complete the repair?

--

Go to Step 14

--

12
  1. Turn the ignition off.
  2. Disconnect the PCM.
  3. Turn the ignition on.
  4. Check the MAP signal circuit for a short to voltage or a short to the 5 volt reference A circuit.
  5. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go to Step 14

Go to Step 13

13

Important: : The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Did you complete the repair?

--

Go to Step 14

--

14

Monitor the MAP sensor on the scan tool with engine idling, while increasing the engine RPM.

Does the MAP value change?

--

System OK

Go to Step 2