Pressure sensor circuit

Description

This dtc is output when the refrigerant pressure is either extremely low (0.19 Mpa [2.0 Kgf/cm2, 28 psi] or less) or extremely high (3.14 Mpa [32.0 Kgf/cm2, 455 psi] or more). The air conditioning pressure sensor, which is installed on the pipe of the high pressure side, detects the refrigerant pressure and sends refrigerant pressure signals to the air conditioning amplifier. The air conditioning amplifier determines the pressure from the signals in accordance with the sensor characteristics, and controls the compressor accordingly.

Wiring diagram

Inspection procedure

1. Check refrigerant

1. 1
   Check the sight glass of the cooler unit refrigerant liquid pipe.
2. 2
   Prepare the vehicle in accordance with the chart below.
3. 3
   Compare the sight glass to the following chart.

   

Hint:

*: If the ambient temperature is higher than usual but cooling is sufficient, bubbles in the sight glass are permissible.

1. 1
   Read value of intelligent tester (reg press sens)
2. 2
   Connect the intelligent tester (with can vim) to the dlc3.
3. 3
   Turn the ignition switch on and turn the intelligent tester main switch on.
4. 4
   Select the item below in the data list, and read the value displayed on the intelligent tester.

   

Ok: the display is as specified in the normal condition column.

3. Check wire harness (pressure sensor - air conditioning amplifier)

1. 1
   Disconnect the a21 pressure sensor connector.
2. 2
   Disconnect the e36 amplifier connector.
3. 3
   measure the resistance of the wire harness side connectors.

Standard resistance

4. Check air conditioning amplifier

1. 1
   Remove the air conditioning amplifier with its connectors still connected.
2. 2
   Measure the resistance of the wire harness side connector

Standard resistance

1. 1
   Turn the ignition switch on.
2. 2
   Measure the voltage of the wire harness side connector.

Standard voltage

1. 1
   Inspect air conditioning pressure sensor
2. 2
   Turn the a/c switch on.
3. 3
   Disconnect the a21 sensor connector.
4. 4
   Connect the three 1.5 V dry cell batteries' positive (+) lead to terminal 3 and the negative (-) lead to terminal 1.

Then connect the voltmeter's positive (+) lead to terminal 2 and the negative (-) lead to terminal 1. Measure the voltage. Ok: the voltage changes in accordance with the refrigerant pressure as shown in the graph.

Replace air conditioning amplifier