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Home >> American Motors >> 1985 >> Alliance Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> 1.4L TBI System >> Component Testing >> Manifold Absolute Pressure (Map) Sensor

Manifold Absolute Pressure (Map) Sensor

  1. Inspect MAP sensor vacuum hose connections at sensor and throttle body. Repair as required. Test MAP sensor output voltage at MAP sensor connector pin B (as marked on sensor body) with the ignition switch on and engine off. See Fig 1 . Output voltage should be 4.0-5.0 volts.
    NOTE: Voltage should drop 0.5-1.5 volts with hot engine, at idle.
    Fig 1: MAP Sensor Terminal Identification If markings on MAP sensor vary from illustration, use markings on sensor.
    G1160
  2. Test pin 12 of ECU connector J2 for 4.0-5.0 volts to verify wiring harness condition. Repair if required.
  3. Check for MAP sensor supply voltage of 4.5-5.5 volts at sensor connector, pin C, with ignition on. Similar voltage should be present at pin 2 of ECU connector J2. Repair or replace wiring harness if required. Test for sensor ground between pin 13 of ECU connector J2 and pin A of sensor connector.
  4. Check for ground from pin 13 of ECU connector J2 to pin F of connector J1. If an open circuit is indicated, check for a good sensor ground on the flywheel housing near the starter motor.
  5. If ground is good, the ECU must be replaced. Before replacing ECU, check to see if pin 13 of ECU connector J2 is shorted to 12 volts. If so, correct the condition and test ECU before replacing. Refer to electronic control unit test.
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