GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 DTC 🢒 DTC 027

Circuit Description

The air conditioning (A/C) system uses an air conditioning pressure (ACP) sensor mounted in the high pressure side of the A/C refrigerant system to monitor the A/C refrigerant pressure. The electronic control module (ECM) uses this information to turn the cooling fans ON at high speed when the A/C refrigerant pressure is high and to keep the A/C compressor disengaged when the A/C refrigerant pressure is excessively high or low.

Conditions for Setting the DTC
    • The ACP sensor reading is above 3 115 kPa (452 psi).
    • This condition is present for 10 seconds.

Diagnostic Aids
    • Inspect the wiring harness for damage. If the wiring harness appears OK, observe the A/C pressure display on the scan tool while moving the connectors and the wiring harnesses related to the ACP sensor. A change in the ACP display on the scan tool will indicate the location of the fault.
    • A fault in the A/C system or inoperative cooling fans may set an ACP DTC.

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Disconnect the air conditioning pressure (ACP) sensor connector.
  2. Turn ON the ignition.
  3. Measure the voltage between the ACP connector terminals 2 and 1.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 3

Go to Step 5

3
  1. Turn the ignition to LOCK.
  2. Connect the ACP sensor connector.
  3. Turn ON the ignition.
  4. Measure the voltage between the engine control module (ECM) connector terminal C15 and ground.

Does the voltage measure below the value specified?

2 V

Go to Diagnostic Aids

Go to Step 4

4

Inspect for a short to voltage in the wire between the ACP connector terminal 3 and the ECM connector terminal C15.

Did you find the condition?

--

Go to Step 8

Go to Step 9

5

Measure the voltage between the ACP connector terminal 1 and ground.

Does the voltage measure within the value specified?

4.5-5.5 V

Go to Step 6

Go to Step 7

6

Inspect the wire between the ACP connector terminal 2 and the ECM connector terminal D15 for a short to the battery voltage.

Did you find the condition?

--

Go to Step 8

Go to Step 10

7

Inspect for a short to battery voltage in the wire between the ACP connector terminal 1 and the ECM connector terminal D8.

Did you find the condition?

--

Go to Step 8

Go to Step 10

8
  1. Turn the ignition to LOCK.
  2. Repair the wire or the connector terminal as needed.
  3. Clear any DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

--

9
  1. Turn the ignition to LOCK.
  2. Replace the ACP sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC.
  3. Clear any DTCs from the ECM.
  4. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

--

10
  1. Turn the ignition to LOCK.
  2. Replace the ECM. Refer to Engine Control Module Replacement .
  3. Perform the Diagnostic System Check.

Did you complete the repair?

--

System OK

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