Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

Manifold Absolute Pressure (MAP) and Manifold Differential Pressure (MDP) Sensors

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OPERATION



See Figures 1 and 2

Only TFI-equipped engines use a MAP sensor for fuel delivery control. The MFI-equipped engines use a MDP sensor for EGR system diagnostics.

The Manifold Absolute Pressure (MAP) sensor measures and responds to the changes in the intake manifold pressure. As manifold pressure changes, the electrical resistance of the sensor also changes. By monitoring the sensor's output voltage, the ECM can calculate the engine load condition, and determine the engine's fuel requirements. When there is high pressure (low vacuum) in the intake manifold, the engine requires more fuel. When there is low pressure (high vacuum) in the intake manifold, the engine requires less fuel. High intake manifold pressure produces a high voltage MAP sensor signal, whereas low intake manifold pressure produces a low voltage MAP sensor signal.



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Fig. Fig. 1: Manifold Differential Pressure (MDP) sensor circuit-1996-98 MFI engines



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Fig. Fig. 2: Cut away view of the internal Manifold Absolute Pressure (MAP) sensor components

The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the ECM to automatically adjust for different altitudes.

The 1996-98 1.6L MFI and 1.8L engines use a Manifold Differential Pressure (MDP) sensor, which functions exactly like the MAP sensor. However, the ECM uses the MDP sensor information only for EGR system self-diagnostics.

The MAP/MDP sensor is mounted on the right-hand side of the firewall.

TESTING



1.3L TFI, 1.6L MFI and 1.8L Engines

See Figures 3, 4 and 5

The 1.3L TFI engine uses a MAP sensor, whereas the 1.6L and 1.8L MFI engines utilize a MDP sensor.

  1. Detach the vacuum hose from the sensor, then disengage the wiring harness connector from the MAP/MDP sensor.
  2.  
  3. Remove the MAP/MDP sensor retaining bolts, then lift the sensor out of the engine compartment.
  4.  
  5. Arrange 3 new 1.5 volt batteries in series (positive-to-negative, positive-to-negative, etc.). Using jumper wires connect the battery assembly negative end to the ground terminal of the sensor, and the positive end of the battery assembly to the Vin terminal.
  6.  



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Fig. Fig. 3: A hand-held vacuum pump and a Digital Volt-Ohmmeter (DVOM) is necessary to properly test the MAP/MDP sensor-MFI engine shown



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Fig. Fig. 4: Although different in appearance, the MAP sensor used on 1.3L TFI engines is tested the same as on MFI engines



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Fig. Fig. 5: Compare the voltage reading of the MAP sensor to this chart

  1. Using a Digital Volt-Ohmmeter (DVOM), switched to the voltmeter function, measure the voltage between the ground terminal and the VOUT terminal of the sensor. For this measurement, ensure that the negative DVOM lead is attached to the ground terminal, and the positive lead is connected to the VOUT terminal. Compare the voltage reading with the accompanying chart.
  2.  

If unfamiliar with metric pressure measurements, divide the barometric pressure column numbers of the chart by 2.54 to calculate the applicable barometric pressure in inches of Mercury (in. Hg).

  1. Connect a hand-held vacuum pump to the MAP/MDP sensor vacuum nipple. While observing the voltage of the sensor (as described in Step 4), slowly apply vacuum to the sensor until 15.7 in. Hg (40 cmHg) vacuum is achieved. As the vacuum increases, the sensor voltage should gradually decrease.
  2.  
  3. If the sensor does not function as described, replace the sensor with a new one.
  4.  

1.6L TFI Engine

  1. Perform a visual inspection of the sensor connector to ensure it is properly engaged. Inspect the connector to ensure there are no bent, corroded, loose or damaged terminals.
  2.  
  3. Perform a visual inspection of the sensor vacuum hose to ensure it is properly attached. Inspect the hose to ensure that it is not cracked, obstructed or leaking.
  4.  
  5. Disengage the wiring harness connector from the sensor.
  6.  
  7. Connect the positive lead of a Digital Volt-Ohmmeter (DVOM), set to the voltmeter function, to the sensor wiring harness connector terminal 1 and a good engine ground.
  8.  
  9. Turn the ignition switch ON , without starting the engine, then measure the voltage at the connector. The voltage should be 4-5 volts at 0 in. Hg vacuum.
    1. If the proper voltage is not present, working backwards, check the sensor circuit to the ECM for a short or open circuit. Be sure to backprobe the circuit connectors; NEVER pierce the wiring.
    2.  
    3. If the voltage is present, proceed to the next step.
    4.  

  10.  
  11. Turn the ignition switch OFF .
  12.  
  13. Reattach the wiring harness connector to the MAP sensor.
  14.  
  15. Connect the positive lead of the Digital Volt-Ohmmeter (DVOM), set to the voltmeter function, to the sensor wiring harness connector terminal 2 and a good engine ground.
  16.  
  17. Connect a hand-held vacuum pump to the vacuum port of the MAP sensor.
  18.  
  19. Turn the ignition switch ON .
  20.  
  21. Usinng the vacuum pump, apply 10 in. Hg of vacuum slowly to the sensor and observe the DVOM. The sensor's resistance should decrease smoothly to 1.32-1.2 volts.
    1. If the reading is within the specified range, the MAP sensor is good.
    2.  
    3. If the values observed are not within the specified range, or do not change smoothly, the MAP sensor is faulty. Replace the sensor with a new one.
    4.  

  22.  

REMOVAL & INSTALLATION



  1. Disconnect the negative battery cable.
  2.  
  3. Detach the vacuum hose from the sensor.
  4.  
  5. Disengage the wiring harness connector from the sensor.
  6.  
  7. Loosen the mounting bolt(s), and remove the sensor from the firewall.
  8.  

To install:
  1. Position the sensor on the firewall, then install and tighten the mounting bolt(s) securely.
  2.  
  3. Reattach the vacuum hose and the wiring harness connector to the sensor.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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