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For 1990-2009 cars only

Object Number: 394191  Size: MF
HVAC Components
Cell 68: ECC Module and Temperature Sensors
Handling ESD Sensitive Parts Notice
Cell 68: ECC Module and Temperature Sensors

Circuit Description

The outside air temperature sensor is a thermistor used in order to control the signal voltage in the electronic climate control (ECC) module. The ECC module control supplies a reference voltage (about 5 volts) on CKT 636 to the sensor. When the outside (ambient) air temperature is cold, the thermistor resistance is high. Therefore, the ECC module will receive a high voltage input. If the outside air temperature is hot, the thermistor resistance is low. The ECC module will receive a low signal voltage input. Refer to Sensor Resistance Table .

Conditions for Setting the DTC

When the ignition switch is in the ON position, the ECC module will detect this DTC any time that CKT 636 is at or near zero voltage.

Action Taken When the DTC Sets

The ECC module will use a default value of -3.3°C (26°F) or 168 A/D counts until the fault is cleared.

Conditions for Clearing the MIL/DTC

This fault will clear as soon as the fault is repaired or when the fault disappears. The system will then return to normal operation. History DTCs may only be cleared by removing and restoring B+ or by using the scan tool.

Diagnostic Aids

Visually inspect the sensor connector and harness for corrosion and damage. The resistance value of the sensor must be 300-170,000 ohms. If the resistance is not within the specified value, replace the sensor.

Test Description

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

  1. This step measures the resistance of the outside air temperature sensor.

  2. This step inspects for a short to ground in CKT 636 (DK GRN/WHT).

  3. This step inspects for intermittents and tests for a malfunctioning ECC module

  4. This step repairs the short to ground in CKT 636 (DK GRN/WHT).

  5. This step replaces a defective outside air temperature sensor.

  6. This step replaces a defective ECC module.

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. Turn the ignition switch to the OFF position.
  2. Disconnect the outside air temperature sensor.
  3. Measure the resistance between sensor terminal A and terminal B.
  4. Compare the reading to the temperature/resistance table. Refer to Sensor Resistance Table .

Is the resistance within the range specified in the table?

--

Go to Step 3

Go to Step 6

3

  1. Disconnect the ECC module.
  2. Inspect for a short to ground in CKT 636 (DK GRN/WHT) at terminal D2 of the ECC module harness connector.

Did you find a short to ground?

--

Go to Step 5

Go to Step 4

4

  1. Reconnect the sensor.
  2. Reconnect the ECC module.
  3. Turn the ignition switch to the ON position.
  4. Clear any ECC module DTCs.

Does the DTC clear?

--

Go to Step 7

Go to Intermittents and Poor Connections Diagnosis in Wiring Systems

5

Repair the short to ground in CKT 636 (DK GRN/WHT).

Is the repair complete?

--

Go to Diagnostic System Check

--

6

Replace the outside air temperature sensor.

Is the replacement complete?

--

Go to Diagnostic System Check

--

7

Replace the ECC module. Refer to Control Assembly Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--