GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Envoy - 4WD 🢒 DTC 🢒 DTC B0185 Solar Load Sensor 1 Circuit Low

Object Number: 394209 Size: SF
HVAC Components
Cell 68: ECC Module and Temperature Sensors
Cell 68: ECC Module and Temperature Sensors
Handling ESD Sensitive Parts Notice

Circuit Description

The sun load temperature sensor is a reverse bias photo diode that measures sun load on the vehicle. The sensor is an input to the electronic climate control (ECC) module. High sensor impedance equates to full darkness. Low sensor impedance equates to bright sunlight.

Conditions for Setting the DTC

With the ignition ON, the ECC module will detect DTC B0185 any time that CKT 590 is at or near zero voltage.

Action Taken When the DTC Sets

The ECC module will use a default value of approximately 200 A/D counts until the fault is cleared.

Conditions for Clearing the MIL/DTC

This fault will clear as soon as the fault goes away or has been repaired. 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
    • The ECC module may set class 2 lost communication DTCs when the body control module (BCM) or the vehicle control module (VCM) is being reprogrammed. After reprogramming, inspect for DTCs in the ECC module. Clear any history U DTCs, then resume diagnostics.
    • Visually inspect the sensor connector and harness for corrosion and damage.

Test Description

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

  1. This step inspects for a short to ground in CKT 590.

    2.

  2. This step inspects for the display of sensor counts in the scan tool.

    3.

  3. This step repairs the short to ground in CKT 590.

    4.

  4. This step replaces a defective sun load temperature sensor.

    5.

  5. This step inspects for a malfunctioning ECC module.

    6.

  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 sun load temperature sensor.
  3. Disconnect the ECC module.
  4. Inspect for a short to ground in CKT 590 (LT BLU/BLK) at terminal C1 of the ECC module connector.

Is the resistance less than the specified value?

5 ohms

Go to Step 4

Go to Step 3

3

  1. Reconnect the sun load temperature sensor.
  2. Reconnect the ECC module.
  3. Turn the ignition switch to the ON position.
  4. Cover up the sun load temperature sensor in the defroster grille.
  5. Read the sun load temperature sensor counts in the scan tool.

Are the counts equal to or less than the specified value?

20 counts

Go to Step 5

Go to Step 6

4

Repair the short to ground in CKT 590 (LT BLU).

Is the repair complete?

--

Go to Diagnostic System Check

--

5

Replace the sun load temperature sensor.

Is the replacement complete?

--

Go to Diagnostic System Check

--

6

  1. Clear the ECC module DTCs.
  2. Inspect for ECC module DTCs.

Does the DTC reset?

--

Go to Step 7

Go to Intermittents and Poor Connections Diagnosis in Wiring Systems

7

Replace the ECC module. Refer to Control Assembly Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--