GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The air conditiong (A/C) evaporator temperature sensor is a variable resistor that measures the temperature of the evaporator. The A/C evaporator temperature sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the signal circuit and a ground for the low reference circuit. If the ECM detects a low signal voltage, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1535 Air Conditioning (A/C) Evaporator Temperature Sensor Circuit Low

Conditions for Running the DTC

    • The ignition is ON or the engine is operating.
    •  DTC P1535 runs continuously once the above condition is met.

Conditions for Setting the DTC

The ECM detects a low voltage condition for more the 1 second.

Action Taken When the DTC Sets - European Emissions

    • The ECM will not illuminate the malfunction indicator lamp (MIL).
    • A history DTCs is stored.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored Failure Records.
    • The A/C compressor operation will be disabled while the low voltage indication exists.

Action Taken When the DTC Sets - Non European Emissions

The malfunction indicator lamp (MIL) will illuminate.

Conditions for Clearing the MIL/DTC - European Emissions

    • The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for 10 seconds.

Conditions for Clearing the MIL/DTC - Non European Emissions

    • The MIL will turn OFF when the diagnostic runs and passes.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for 10 seconds.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

Connect End View Reference: HVAC Connector End Views

1

Did you perform the Diagnostic System Check - HVAC System?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the DTC Info with a scan tool.

Did DTC P1535 fail this ignition?

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Go to Step 4

Go to Step 3

3

  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
  3. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Symptoms - Engine Controls

4

  1. Turn OFF the ignition.
  2. Disconnect the air conditioning (A/C) evaporaror temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage between the A/C evaporator temperature sensor signal circuit and a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 5

Go to Step 6

5

Probe the low reference circuit of the A/C evaporator temperature sensor with a DMM connected to battery voltage.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 7

6

Test the signal circuit of the A/C evaporator temperature sensor for one of the following conditions:

    • An open
    • A short to ground
    • A short to voltage
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 12

Go to Step 9

7

Test the low reference circuit of the A/C evaporator temperature sensor for an open or high resistance. 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

Test for an intermittent and for a poor connection at the A/C evaporator 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

Test for an intermittent and for a poor connection at the engine control module (ECM). 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 evaporator temperature sensor. Refer to Intake Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

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11

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

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12

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 13

13

Are there any DTCs that have not been diagnosed?

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Go to Diagnostic Trouble Code (DTC) List

System OK