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For 1990-2009 cars only
Makes 🢒 Oldsmobile 🢒 1997 🢒 Aurora 🢒 DTC 🢒 DTC P1537 Air Conditioning (A/C) Request Circuit Low Voltage

Object Number: 13332 Size: SF
Engine Controls Components
A/C Compressor Controls
OBD II Symbol Description Notice
ESD Notice
ESD Notice

Circuit Description

This diagnostic indicates very low refrigerant pressure or an open low pressure switch/circuit by comparing the A/C request discrete line, which contains the low pressure switch, to the HVAC serial data A/C request status. If the A/C request line is low, no voltage present, while the HVAC serial data is requesting A/C operation then DTC P1537 is set.

Conditions for Setting the DTC

Test Conditions

    •  DTC P1605 not set.
    •  A/C compressor requested by the HVAC programmer serial data.

Failure Condition

A/C request line low, no voltage present, for 30 seconds.

Action Taken When the DTC Sets
    •  Disable A/C compressor.
    •  The Malfunction Indicator Lamp (MIL) will not illuminate.
    •  No message will be displayed.

Conditions for Clearing the DTC

    •  A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
    •  A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
    • Use a scan tool to clear DTCs.
    • Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.

Diagnostic Aids

If fault is not present operate the vehicle with a manifold gauge connected and watch for low A/C system pressure with engine and A/C ON for an extended period.

Whenever A/C request line is checked for voltage the engine must be running.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. Checking if fault is present.

    2.

  2. Checking if fault is circuit or sensor / pressure problem. Disabling the A/C compressor is required for system protection.

    3.

  3. Checking for voltage to switch.

    4.

  4. Checking for the A/C Low Pressure Switch (A/C Request) circuit shorted to ground.

    5.

  5. Checking for an open in the A/C Low Pressure Switch (A/C Request) circuit.

    6.

  6. Checking for voltage output from HVAC.

Step

Action

Value(s)

Yes

No

1

Was the On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

2
  1. Start and idle the engine.
  2. Turn the HVAC A/C controls to A/C ON, maximum cool and maximum blower.
  3. Using a scan tool note the DTC information Fail This Ign..
  4. Wait one minute.

Has this DTC set?

--

Go to Step 3

Fault not present. Refer to Diagnostic Aids

3
  1. Disconnect A/C low pressure switch connector.
  2. Remove the HVAC COMPRESSOR fuse or the A/C compressor clutch relay.
  3. Using a scan tool note the A/C Request display.
  4. With engine and A/C still ON, jumper A/C low pressure switch terminals A and B together.

Does A/C Request display Yes?

--

Go to Step 8

Go to Step 4

4
  1. Reinstall HVAC compressor fuse or the A/C compressor clutch relay.
  2. Remove the jumper.
  3. With engine and A/C still ON, use DVM J 39200 and measure the voltage to ground at A/C low pressure switch connector terminal A.

Is the voltage measured the same or more than the value specified?

10.5 volts

Go to Step 5

Go to Step 7

5
  1. Record the fluid life indexes, turn the key to OFF and wait 30 seconds.
  2. Disconnect PCM connector C1.
  3. Measure the resistance to ground at A/C low pressure switch terminal B.

Is the resistance less than the value specified?

10K ohms

Go to Step 6

Go to Step 9

6

Measure the resistance between PCM connector C1 terminal 76 and A/C low pressure switch terminal B.

Is the resistance the same or less than the value specified?

5 ohms

Go to Step 14

Go to Step 10

7

With engine and A/C still ON, use DVM J 39200 and measure the voltage to ground at HVAC terminal D15.

Is the voltage the same or more than the value specified?

10.5 volts

Go to Step 11

Go to Step 13

8
  1. Reinstall HVAC compressor fuse or the A/C compressor clutch relay.
  2. Connect a manifold gauge set to A/C system and note A/C low side pressure in system.

Is A/C low side pressure more than the value specified?

38 psi

Go to Step 12

System pressure is low. Go to Section 1, Heating and Air Conditioning.

9

Repair the short to ground in the A/C Low Pressure Switch signal circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

10

Repair the open in the A/C Low Pressure Switch signal circuit.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

11

Repair the open in the A/C Low Pressure Switch power feed circuit between the switch and HVAC prog.or poor terminal contact at the switch or HVAC prog.

Is the repair complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

12

Replace the A/C low pressure switch. Refer to Section 1, Heating and Air Conditioning .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

13

Replace the HVAC programmer. Refer to Section 1, Heating and Air Conditioning .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--

14
  1. Check terminal contact at the PCM connector C1 terminal 76.
  2. Repair terminal contact if needed.

Was terminal contact repaired.

--

Go to Powertrain Control Module Diagnosis for Verify Repair

Go to Step 15

15

Replace the PCM. Refer to PCM Replacement/Programming .

Is the replacement complete?

--

Go to Powertrain Control Module Diagnosis for Verify Repair

--