Manifold Pressure/Vacuum Sensor: Testing and Inspection
Output Voltage Check1. Remove ECM according to previously outlined.
2. Connect couplers to ECM securely.
3. With coupler connected to ECM, connect digital type voltmeter as shown and check that ECM supply voltage 4.75- 5.25V is applied to coupler terminal B1.
4. Check output voltage at coupler terminal B3. Note that it varies with atmospheric pressure and altitude. Also, start engine, if it can, and check if output voltage varies.
Output voltage (ECM supply voltage 4.75 - 5.25V, ambient temp. 1O - 40°C, 50 - 104°F)
NOTE: Note that atmospheric pressure varies depending on weather conditions as well as altitude. Take that into consideration when performing above check.
If check result is not satisfactory in previous step 3) or 4), check MAP sensor and its circuit according to Diagnostic Flow Chart for Code No.31.
NOTE: If output voltage does not vary when engine is started, it is possible that vacuum hose and/or filter are clogged. Clean them. Another possibility is that filter in MAP sensor is clogged from freezing. If it is suspected, leave it at room temperature (2O°C, 68°F) for a while and recheck.
5. Upon completion of checking, install ECM and connect ECM coupler securely.
MAP Sensor Individual Check
1. Disconnect MAP sensor vacuum hose from filter.
2. Disconnect coupler from MAP sensor.
3. Remove MAP sensor.
4. Arrange 3 new 1.5V batteries in series (check that total voltage is 4.5 - 5.OV) and connect its positive terminal to "VIN" terminal of sensor and negative terminal to "Ground" terminal. Then check voltage between "Vout" and "Ground". Also, check if voltage reduces when vacuum is applied up to 40 cmHg by using vacuum pump.
Output voltage (VIN voltage 4.5 - 5.OV, ambient temp. 2O - 30°C, 68 - 86°F)
If check result is not satisfactory, replace MAP sensor.
5. Install MAP sensor and connect vacuum hose securely.
6. Connect MAP sensor coupler securely.