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Home >> Jeep >> 1990 >> Wagoneer >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - 2.5L >> Manifold Absolute Pressure Sensor >> Functional Test
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Functional Test

  1. Inspect Manifold Absolute Pressure (MAP) sensor vacuum hose connections at throttle body and sensor. Repair as necessary. Test MAP sensor output voltage at MAP sensor connector terminal "B" (as marked on sensor body) with ignition on and engine off. Output voltage should be 4-5 volts. Voltage should drop to 1.5-2.1 volts with a hot, neutral idle condition.
  2. Test ECU terminal No. 33 for the same voltage as above to verify wire harness condition. Repair as necessary. Test MAP sensor supply voltage at sensor connector terminal "C" with ignition on. The voltage should be 4.5-5.5 volts. Same voltage should also be at terminal No. 16 of ECU wire harness connector. Repair or replace wire harness as necessary.
  3. Test MAP sensor ground circuit at sensor connector terminal "A" and ECU connector terminal No. 17. See Figure or Figure . Repair wire harness as necessary. Test MAP sensor ground circuit at ECU connector between terminal No. 17 and terminal No. 2 with ohmmeter.
  4. If ohmmeter indicates an open circuit, inspect for defective sensor ground connection on flywheel/drive plate housing near starter motor. If ground connection is good, replace ECU. If terminal No. 17 has a short circuit to 12 volts, correct condition before replacing ECU.
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