1990 Jeep Wrangler Laredo, AutomaticFACTORY OEM SERVICE PROCEDURE

Manifold Absolute Pressure Sensor Functional Test

  1. Inspect the MAP sensor vacuum hose connections at the throttle body and the MAP sensor. See Fig 1. Repair vacuum hose or connections as necessary.
    Fig 1: Manifold Absolute Pressure (MAP) Sensor Connectors
    G50C04612Courtesy of CHRYSLER MOTORS.
  2. With the ignition switch ON and engine OFF, test the MAP sensor output voltage at the MAP sensor connector terminal "B". See Fig 1. With a hot idle condition, the voltage reading should drop to between 0.5-1.5 volts.
  3. Test ECU terminal "C-6" for the same voltage as described in step 2) to verify the wiring harness. Repair as necessary.
  4. Test the MAP sensor supply voltage at the sensor connector terminal "C" with the ignition ON. Voltage reading should be between 4.5-5.5 volts. Check that the voltage reading at terminal "C-14" is also 4.5-5.5 volts.
  5. Repair or replace the wire harness as necessary.
  6. Test the MAP sensor ground circuit at the sensor connector terminal "A" and ECU connector terminal "D-3". Repair the wire harness as necessary.
  7. Using an ohmmeter, test the MAP sensor ground circuit at the ECU connector between terminal "D-3" and terminal "B-ll". If an open circuit is indicated, check for a defective sensor ground connection. The MAP sensor ground is located on the right side of the engine block.
  8. If, after performing step 7), the ground connection is verified to be good, check for a short to 12 volts at terminal "D-3". If a short is found, repair the short and then replace the ECU.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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