GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 DeVille 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC P1531 A/C Temperature Sensor Circuit Malf

Circuit Description

The dash integration module (DIM) monitors the refrigerant temperature through the A/C refrigerant low temperature sensor. When the refrigerant is cold, the sensor resistance and signal voltage are high. When the refrigerant is warm, the sensor resistance and signal voltage are low. The DIM will not request A/C compressor clutch engagement when the refrigerant temperature is low enough to cause the A/C evaporator core to freeze.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The DIM detects the signal circuit is less than 127°C (261°F) or greater than -36°C (-34°F).

Action Taken When the DTC Sets
    • A default value will be used by the DIM.
    • The A/C compressor clutch will not engage.

Conditions for Clearing the DTC
    • The DTC will become history if the DIM no longer detects a failure.
    • The history DTC will clear after 40 fault free ignition cycles.
    • The DTC can be cleared with a scan tool.

Diagnostic Aids

Test the following conditions:

    • Visually inspect the sensor for contamination or damage.
    • Inspect for the following that may affect the sensors accuracy.
       - A malfunction within the refrigerant system causing low pressure.
       - Visually inspect the A/C components and lines for damage:
    • If condition not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper operation of the circuit in the high voltage range.

    2.

  2. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

    3.

  3. Perform the recalibration procedure for the dash integration module.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Blower Control Schematics , HVAC Compressor Control Schematics , and HVAC Air Delivery/Temperature Control Schematics

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Evaporator Temp. parameter in the Dash Integration Module A/C Information data list.

Does the scan tool indicate that the Evaporator Temp. parameter is within the specified range?

-36°C to 127°C (-34°F to 261°F)

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the A/C refrigerant low temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Evaporator Temp. parameter in the Dash Integration Module A/C Information data list.

Does the scan tool indicate that the Evaporator Temp. parameter is less than the specified value?

-36°C (-34°F)

Go to Step 4

Go to Step 5

4

  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the signal circuit of the A/C refrigerant low temperature sensor and the sensor returncircuit of the A/C refrigerant low temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Evaporator Temp. parameter in the Dash Integration Module A/C Information data list.

Does the scan tool indicate that the Evaporator Temp. parameter is greater than the specified value?

127°C (261°F)

Go to Step 8

Go to Step 6

5

Test the signal circuit of the A/C refrigerant low temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

Test the signal circuit of the A/C refrigerant low temperature sensor or a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

Test the sensor return circuit of the A/C refrigerant low temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Inspect for poor connections at the harness connector of the A/C refrigerant low temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Inspect for poor connections at the harness connector of the dash integration module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Replace the A/C refrigerant low temperature sensor. Refer to Temperature Sensor Replacement - Low Side .

Did you complete the replacement?

--

Go to Step 12

--

11

Important: Perform the recalibration procedure for the dash integration module.

Replace the dash integration module. Refer to Dash Integration Module Replacement in Body Control Systems.

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK