See Figure 1
The manifold absolute pressure sensor is mounted on the dash panel behind the engine. The MAP sensor reacts to absolute pressure in the intake manifold and provides an input voltage to the ECU. Manifold pressure is used to supply mixture density information and ambient barometric pressure information to the ECU. A hose from the intake manifold provides the input pressure.
- Inspect the MAP sensor vacuum hose connection at the throttle body and sensor and repair as necessary.
- Test the MAP sensor output voltage at the MAP sensor connector terminal B (as marked on the sensor body) with the ignition switch and the engine OFF . The output voltage should be 4-5 volts.
The voltage should drop to 0.5-1.5 volts with a hot, neutral idle speed condition.
- Test ECU terminal C-6 for the same voltage as in Step 2 to verify the wire harness condition and repair as necessary.
- Test the MAP sensor supply voltage at the sensor connector terminal C with the ignition ON . The voltage should be 4.5-5.5 volts. The same voltage should be present at terminal C-14 of the ECU wire harness connector. Repair or replace the wire harness as necessary. If the ECU is suspect, use Diagnostic Tester M.S.1700, or equivalent, to test ECU function. Follow the manufactures instructions.
- Test the MAP sensor ground circuit at the sensor connector terminal A and ECU connector terminal D-3. Repair the wire harness as necessary.
- Test the MAP sensor ground circuit at the ECU connector between terminal D-3 and terminal B-11 with an ohmmeter. If the ohmmeter indicates an open circuit, check for a defective sensor ground connection located on the right side of the cylinder block. If the ground connection is good, replace the ECU.
If terminal D-3 has a short circuit to 12 volts, correct this condition before replacing the ECU.