Cherokee 2WD L4-150 2.5L VIN H TBI (1988)
Manifold Pressure/Vacuum Sensor: Testing and Inspection
MAP Sensor Description
NOTE: Before starting the test, check the condition of the electrical and vacuum hose connections. Repair if needed.
1.
Turn the ignition switch ON (the engine should remain off), and test the voltage from connector terminal B to ground with a voltmeter.
Voltage should be between 4 to 5 volts. With the engine started, warmed to normal operating temperature, and idling, the voltage output
should drop to 1.5 to 2.1 volts.
2.
Check for voltage at ECU electrical terminal 33 under the same conditions as in step 1. The voltage readings should be the same as in step 1.
If the voltages are different, then the wiring harness should be suspected as the problem area.
3.
Check the supply voltage to the sensor by connecting a voltmeter to connector terminal C and a ground. Voltage reading should be 5 +/- 0.5
volts with the ignition switch ON. There should also be 5 +/- 0.5 volts at ECU electrical terminal 16. Repair wiring harness if necessary.
4.
Check the sensor ground circuit between electrical terminal A on the sensor and ECU connector terminal 17. Connect one lead of an
ohmmeter to electrical terminal A of the sensor and the other to ECU connector terminal 17. The ohmmeter should indicate continuity.
Repair wiring harness if necessary.
5.
Check the sensor ground circuit at the ECU electrical connector. Connect an ohmmeter between terminals 17 and 2 of the ECU electrical
connector. If the ohmmeter does not indicate continuity, check the sensor ground connection on the flywheel/drive plate housing near the
starter. If the ground connection is good, replace the ECU.
WARNING:If ECU connector terminal 17 has a short to 12 volts (battery voltage), this is most likely the reason the first ECU failed;
consequently, it is imperative that this circuit be repaired before installing a new ECU.
