GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Century (China) 🢒 Engine 🢒 Engine Controls - 2.5L (LB8) and 3.0L (L46) 🢒 Manifold Absolute Pressure Sensor Circuit Diagnosis

Object Number: 516716 Size: SF
Engine Controls Components
A/C Pressure Sensor, TP, MAP, ECT and IAT
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The manifold absolute pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the PCM varies from below 2 volts at idle (high vacuum) to above 4 volts with the key ON, engine not running or at wide open throttle (WOT) (low vacuum). The MAP sensor is used to determine manifold pressure changes while the EGR flow test diagnostic is being run, refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient . Also to update the barometric pressure reading (BARO), and as a enabling factor for other diagnostics. The Powertrain Control Module (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, refer to DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage will be set. If the PCM detects a MAP signal voltage that is excessively low, refer to DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage 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, check the 3X reference circuits from the ignition control (IC) module 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 (high voltage or low voltage) is when the engine is started, the high or low voltage MAP sensor DTCs will set.
    •  Poor connection at the PCM--Inspect harness connectors for:
       - Backed out terminals
       - Improper mating
       - Broken locks
       - Improperly formed or damaged terminals
       - Poor terminal to wire connection
    • Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    •  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 connectors and wiring harnesses related to the sensor. A change in the display will indicate 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

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. Inspect for the following conditions:
    2. •  MAP sensor seal missing or damaged
    •  Vacuum hoses disconnected, damaged, or incorrectly routed.
    •  Intake manifold vacuum leaks.
    •  Vacuum leaks at throttle body.
    •  Vacuum leaks at the EGR gasket.
    •  Positive crankcase ventilation valve faulty, missing, or incorrectly installed.
  2. If a problem is found, repair as necessary.

Did you find and correct any of the conditions?

--

Go to Step 14

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the MAP sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the MAP sensor voltage parameter.

Does the scan tool indicate that the MAP sensor voltage parameter is more than the specified value?

0.0 V

Go to Step 4

Go to Step 11

4
  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the 5 volt reference A circuit of the MAP sensor and the signal circuit of the MAP sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the MAP sensor parameter.

Does the scan tool indicate that the MAP sensor parameter is near the specified value?

4.95 V

Go to Step 5

Go to Step 8

5
  1. Connect a test lamp between battery positive voltage and the MAP sensor signal circuit at the MAP sensor harness connector.
  2. Observe the MAP sensor voltage parameter on the scan tool.

Does the scan tool indicate that the MAP sensor voltage parameter is near the specified value?

4.95 V

Go to Step 6

Go to Step 8

6
  1. Turn OFF the ignition.
  2. Inspect for poor connections at the harness connector of the MAP sensor.
  3. If a problem is found, repair as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 7

7
  1. Test the ground circuit for high resistance, an open between the PCM and the MAP sensor, or for a poor connection at the PCM.
  2. If a problem is found, repair as necessary. Refer to Measuring Voltage Drop , Wiring Repairs and Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

8
  1. Test the 5 volt reference A circuit for high resistance, an open between the PCM and the MAP sensor, or a poor connection at the PCM.
  2. If a problem is found, repair as necessary. Refer to Measuring Voltage Drop , Wiring Repairs and Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

9
  1. Turn OFF the ignition.
  2. Test the signal circuit of the MAP sensor for 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 Measuring Voltage Drop , Wiring Repairs and Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

10
  1. Test the signal circuit of the MAP sensor for a poor 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 you find and correct the condition?

--

Go to Step 14

Go to Step 13

11
  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Test the signal circuit of the MAP sensor 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 Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

--

12

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

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

13

Important::  Perform the set up procedure for the PCM.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Did you find and correct the condition?

--

Go to Step 14

--

14

With the engine idling, monitor the MAP sensor with a scan tool while increasing the engine RPM.

Does the MAP sensor value change?

--

System OK

Go to Step 2