Toyota Celica 1994-1998 Repair Guide

Manifold Air Pressure (MAP) Sensor

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OPERATION



This sensor advises the ECM of pressure changes in the intake manifold. It consists of a semi-conductor pressure converting element which converts a pressure change into an electrical signal. The ECM sends a reference signal to the MAP sensor; the change in air pressure changes the resistance within the sensor. The ECM reads the change from its reference voltage and signals its systems to react accordingly.

TESTING



See Figures 1, 2, 3 and 4

  1. Disconnect the MAP sensor wiring.
  2.  
  3. Turn the ignition switch ON .
  4.  
  5. Using a voltmeter, measure the voltage between the connector terminals VC and E2 of the wiring harness side. Voltage should be 4.5-5.5 volts.
  6.  



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Fig. Fig. 1: MAP sensor terminal identification



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Fig. Fig. 2: Measuring voltage terminals VC and E2 of the MAP sensor

  1. Turn the ignition switch to LOCK .
  2.  
  3. Reattach the MAP sensor wiring.
  4.  
  5. To inspect the power output of the sensor, turn the ignition switch to the ON position.
  6.  
  7. Disconnect the vacuum hose from the sensor.
  8.  
  9. Connect the voltmeter to terminals PIM and E2 of the ECM, and measure the output voltage under ambient atmospheric pressure.
  10.  
  11. Apply vacuum to the MAP sensor in 3.94 inch Hg. (13.3 kPa) segments to 19.69 inch Hg. (66.7 kPa).
  12.  
  13. Measure the voltage drop from step 8 above for each segment.
  14.  



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Fig. Fig. 3: MAP sensor specifications



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Fig. Fig. 4: Connect an ohmmeter to terminals PIM and E2 of the ECM and measure the output voltage

  1. Reattach the vacuum hose to the sensor.
  2.  

REMOVAL & INSTALLATION



See Figure 5



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Fig. Fig. 5: View of the MAP sensor attached to the firewall

Label and disconnect all hoses and wiring to the MAP sensor. Unbolt the sensor from the firewall. Attach ands secure a new sensor, then connect all wires and hoses.

 
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