Manifold Pressure/Vacuum Sensor: Testing and Inspection

Pressure Sensor Schematic:

The intake air flow measuring system is a pressure sensor connected with a hose to the intake plenum. A faulty pressure sensor will set code 23 in the on-board diagnostic system. A disconnected or broken pressure sensor hose will set code 65. Refer to the schematic diagram and test the sensor with the diagnostic chart.

Wire color code identification:

L: Blue
B: Black
Y: Yellow
G: Green
R: Red
W: White
Br: Brown
Lg: Light green
Gr: Gray

Pressure Sensor Diagnostic Chart:

PRESSURE SENSOR DIAGNOSTIC CHART

Pressure Sensor Harness:

Pressure Sensor Testing:

CHECK ECU HARNESS

1. With ignition switch "OFF," disconnect ECU connector.
2. Measure resistance between ECU connector and pressure sensor connector as follows:

Connector & terminal: Resistance:
(F121)1-(F115)2 Below 1 Ohm
(F121)2-(F115)2 Below 1 Ohm
(F121)3-(F115)1 Below 1 Ohm
(F121)2-(F115)3 Below 1 Ohm

3. Connect ECU connector and measure resistance between pressure sensor connector (F115) terminals:

Connector & terminal: Resistance:
(F115)1-(F115)2 Infinite
(F115)3-(F115)2 Infinite

CHECK PRESSURE SENSOR VOLTAGE

1. With ignition "ON," voltage across pressure sensor connector terminals should be as follows:

Connector & terminal: Voltage:
(F115)3-(F115)2 4.5-5.5V

2. Connect pressure sensor connector and turn ignition "ON."
3. Measure voltage across ECU connector terminals as follows:

Connector & terminal: Voltage: [1]
(F121)3-(F121)1 3.4-3.8V
(F121)3-(F121)2 3.4-3.8V

4. Start and idle engine. Measure voltage across ECU connector terminals as follows:

Connector & terminal: Voltage: [1]
(F121)3-(F121)1 1.6-2.1V
(F121)3-(F121)2 1.6-2.1V

[1] With atmospheric pressure at 760mmHg (29.92 inHg).