Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Manifold Absolute Pressure (Map) Sensor Test
1987 Jeep Cherokee LimitedSECTION Manifold Absolute Pressure (Map) Sensor Test
- 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.
- 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.
- Test ECU terminal "C-6" for the same voltage as described in step 2) to verify the wiring harness. Repair as necessary.
- 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.
- Repair or replace the wire harness as necessary.
- Test the MAP sensor ground circuit at the sensor connector terminal "A" and ECU connector terminal "D-3". Repair the wire harness as necessary.
- 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.
- 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.