GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 DTC 🢒 DTC B1348 Very Low A/C Refrigerant Pressure

Object Number: 506753 Size: MF
HVAC Components
HVAC Compressor Control Schematics (Cell 67: A/C High and Low Pressure Sensors, A/C Compressor Relay)
Handling ESD Sensitive Parts Notice
Power Distribution Schematics

Circuit Description

In the process of controlling the compressor clutch, the heater and A/C programmer monitors certain system inputs for an indication of a low refrigerant charge. The heater and A/C programmer monitors the normally closed low refrigerant pressure switch at pin D14. Inspect the status of the low pressure switch prior to the compressor engagement. If the switch opens, the following actions occur:

    • The heater and A/C programmer sets DTC B1348.
    • The message VERY LOW REFRIGERANT--A/C COMPRESSOR OFF displays on the driver information center (DIC).

If a DTC B1348 is set, the compressor clutch disengages and remains disengaged until DTC B1348 is cleared.

Failure Conditions
    • The low refrigerant switch remains open for several minutes.
    • The vehicle must be traveling above 48 km/h (30 mph) for at least 30 seconds. This code may not set at idle or in city traffic.

Action Taken When the DTC Sets
    • The system disables the compressor until the DTC is cleared.
    • The system disables the VERY LOW REFRIGERANT--A/C COMPRESSOR OFF message on the DIC.

Test Description

  1. Perform the Diagnostic System Check before continuing with the diagnosis of this DTC.

    2.

  2. This test inspects the current state of the low pressure switch.

    3.

  3. This test inspects the circuits to the low pressure switch.

    4.

  4. This test inspects for a restriction in the refrigerant system.

    5.

  5. This test inspects the HVAC refrigerant system pressure.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Ensure that the ambient temperature display is above 6°C (42°F).
  2. Turn the ignition switch to the ON position.
  3. Connect a Scan Tool .
  4. Display LOW PRESSURE SW on the Scan Tool .
  5. Note the status.

Is the status OPEN?

--

Go to Step 3

Go to Step 4

3

  1. Remove the low refrigerant pressure switch connector.
  2. Connect a fused jumper between the harness connector pin A and pin B. Refer to Using Fused Jumper Wires in Wiring Systems.
  3. Note the status.

Does the status remain OPEN (switches closed)?

--

Go to Step 5

Go to Step 12

4

  1. Connect a pressure gauge set to the refrigerant system service fittings.
  2. Start the engine.
  3. Select 75 AUTO.
  4. Use a Scan Tool in order to compare the gauge pressure to the low and high side temperature. Use the refrigerant temperature-to-pressure conversion chart.

Is the calculated and gauge pressure within the specified value?

10 %

Go to Step 8

Go to Step 9

5

Measure the voltage from the jumper to ground. Refer to Measuring Voltage in Wiring Systems.

Is the voltage equal to or greater than the specified value?

8 V

Go to Step 6

Go to Step 7

6
  1. Inspect for an open in CKT 603.
  2. If the CKT is not open, inspect for good terminal contact. Refer to Testing for Electrical Intermittents in Wiring Systems.
  3. If the contact is OK, replace the heater and A/C programmer. Refer to Programmer Replacement .

Did you complete the repair?

--

Go to Step 15

--

7

Repair the open or short to ground on switch feed 339 or replace the blown fuse. Refer to Wiring Repairs in Wirning Systems.

Did you complete the repair?

--

Go to Step 15

--

8
  1. Display LOW PRESSURE SW on the Scan Tool .
  2. Observe the status while manipulating the wiring to the low pressure switch.

Does the display cycle from HI to LO?

--

Go to Step 10

Go to Step 11

9

Inspect for a restriction within the refrigerant system between the temperature sensor and the service connection gauge that did not agree.

Did you complete the repair?

--

Go to Step 15

--

10
  1. Repair the intermittent open or short in the wiring to the switch. Refer to Wiring Repairs in Wiring Systems.
  2. Ensure that the heater and A/C programmer terminal contacts are OK. Refer to Testing for Electrical Intermittents in Wiring Systems.

Did you complete the repair?

--

Go to Step 15

--

11

Replace the low pressure switch. Refer to Temperature Sensor Replacement - Low Side .

Did you complete the repair?

--

Go to Step 15

--

12

  1. Connect an A/C pressure gauge to the LO side (open) fitting.
  2. Observe the pressure.

Is the pressure above the specified value?

10 psi

Go to Step 13

Go to Step 14

13
  1. Inspect for a good terminal contact at the low refrigerant pressure switch. Refer to Testing for Electrical Intermittents in Wiring Systems.
  2. If the contact is OK, replace the switch. Refer to Temperature Sensor Replacement - Low Side .

Did you complete the repair?

--

Go to Step 15

--

14
  1. Leak test the system and repair any leaks. Refer to Leak Testing .
  2. Recharge the A/C system as necessary. Refer to Refrigerant Recovery and Recharging .

Did you complete the repair?

--

Go to Step 15

--

15
  1. Use the Scan Tool in order to clear the DTC.
  2. Verify proper operation of the system.

Did you complete the repair?

--

Go to Diagnostic System Check

--