Manifold Absolute Pressure Sensor Circuit Diagnosis. Buick GL7 (Export) 2000

For 1990-2009 cars

### Circuit Description

The manifold absolute pressure (MAP) sensor responds to changes in the intake manifold vacuum. The MAP sensor signal voltage to the PCM varies from less than 2 volts at idle to more than 4 volts with the key ON and the engine not running or at wide open throttle (WOT). The MAP sensor is used to update the barometric pressure reading (BARO), as a enabling factor for other diagnostics, and to determine any manifold pressure changes while the EGR flow test diagnostic is being run. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient . The powertrain control module (PCM) monitors the MAP signal for voltages outside the normal range of the MAP sensor. If the PCM detects a MAP signal voltage that is excessively high, DTC P0108 will be set. If the PCM detects a MAP signal voltage that is excessively low, DTC P0107 will be set.

### Diagnostic Aids

Inspect for the following conditions:

• | Monitor the MAP sensor using a scan tool. If the MAP sensor does not respond to throttle changes, inspect 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 the MAP sensor voltage when the engine is started, the high or low voltage MAP sensor DTCs will set.

• | A poor connection at the PCM. Inspect the harness connectors for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal-to-wire connections

- | Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

• | A damaged harness. 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 | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn the ignition ON leaving the engine OFF.
2. Observe and record the MAP sensor kPa display.

Is the value determined by altitude and weather greater than the specified values?

65 kPa @ altitude

95 kPa @ sea level

Go to Step 3

Go to Step 6

3

1. Remove the MAP sensor from the engine vacuum source. Leave the MAP sensor connected to the engine harness.
2. Connect a J 23738-A hand vacuum pump to the MAP sensor.
3. Observe the MAP sensor kPa as you SLOWLY apply vacuum 1 in. Hg. at a time.

Each one inch of vacuum should result in a 3 to 4 kPa drop in the MAP sensor display. Observe the MAP sensor display for a skip or jump while increasing vacuum up to 20 in. Hg.

Did you observe a skip or jump?

--

Go to Step 13

Go to Step 4

4 | Observe the MAP sensor kPa display with 20 in. Hg. of vacuum applied to the sensor. Is the kPa less than the value specified? | 34 kPa | Go to Step 5 | Go to Step 6
5 | Disconnect the MAP sensor from the hand held vacuum pump. The MAP sensor display should return to the value specified in Step 2. Does the MAP sensor display return to the value recorded earlier? | -- | System OK | Go to Step 13

6

1. Disconnect the MAP sensor from the engine harness.
2. Observe the MAP sensor VOLTAGE display on the scan tool.

Is the voltage greater than the value specified?

0.0 V

Go to Step 9

Go to Step 7

7

1. Jumper the MAP sensor 5 volt reference circuit to the MAP sensor signal circuit using a fused jumper.
2. Observe the MAP sensor VOLTAGE display on the scan tool.

Is the voltage within the value range specified?

4.8 - 5.2V

Go to Step 8

Go to Step 10

8

1. Remove the jumper.
2. Probe the MAP sensor ground circuit with a test lamp connected to battery positive voltage. Refer to Troubleshooting with a Test Lamp , and Testing for Continuity in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 11

9 | Test the signal circuit for a short to voltage. This short will have resistance as a complete short would have set a DTC. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 2 | Go to Step 14
10 | Test the 5 volt reference and the signal circuit for high resistance. Refer to Testing for Continuity , Measuring Voltage Drop , and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 2 | Go to Step 14
11 | Test the sensor ground circuit for high resistance. Refer to Testing for Short to Ground , and Wiring Repairs in Wiring Systems. Did you find and correct the concern? | -- | Go to Step 2 | Go to Step 14
12 | Inspect the MAP sensor connector for poor connection or terminal contact. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 2 | Go to Step 13
13 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 2 | --
14 | Inspect the PCM for poor connection or terminal contact. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 2 | Go to Step 15
15 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | Go to Step 2 |