GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Blazer - 4WD - RHD 🢒 DTC 🢒 DTC B0186 Solar Load Sensor 1 Circuit High

Object Number: 425170 Size: MF

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 module. High sensor impedance equates to full darkness. Low sensor impedance equates to bright sunlight.

Conditions for Setting the DTC

When the ignition switch in in the ON position, the electronic climate control module will detect DTC B0186 any time CKT 590 (LT BLU) is at or near 5 volts or higher.

Action Taken When the DTC Sets

The electronic climate control 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 can only be cleared by removing and restoring B+ or by using the scan tool.

Diagnostic Aids
    • The electronic climate control 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 electronic climate control 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 B+ on CKT 590.

    2.

  2. This step determines is the short to B+ is in CKT 590 or in the electronic climate control module.

    3.

  3. This step inspects for an open in CKT 552.

    4.

  4. This step reads the sun load temperature sensor counts.

    5.

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

    6.

  6. This step repairs an open in CKT 552.

    7.

  7. This step inspects for intermittents and tests for a malfunctioning electronic climate control module.

    8.

  8. This step replaces a defective electronic climate control module.

    9.

  9. This step inspects for 5 volts on CKT 590.

    10.

  10. This step determines if the open is in CKT 590 or in the electronic climate control module.

Step

Action

Value(s)

Yes

No

Tools Required

    • Scan Tool
    • J 39200 Digital Multimeter (DMM)
    • J 35616-A Connector Test Adapter Kit

1

Was the Diagnostic System Check performed?

--

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. Turn the ignition switch to the ON position.
  4. Measure the voltage at terminal A of the sun load temperature sensor harness connector and ground.

Is battery voltage present?

--

Go to Step 3

Go to Step 12

3

Inspect for a short to B+ in CKT 590 (LT BLU/BLK).

Did you find a short to B+?

--

Go to Step 4

Go to Step 11

4

Repair the short to B+ in CKT 590 (LT BLU/BLK).

Is the repair complete?

--

Go to Diagnostic System Check

--

5

Inspect for continuity to ground at terminal B of the sun load temperature sensor harness connector and ground.

Is continuity present?

--

Go to Step 6

Go to Step 8

6

  1. Turn the ignition switch to the OFF position.
  2. Reconnect the sun load temperature sensor.
  3. Turn the ignition switch to the ON position.
  4. Place an incandescent shop light over the sun load temperature sensor in the defroster grille.
  5. Read the sun load temperature sensor counts in the scan tool.

Are the sun load temperature sensor counts above the specified value?

250 counts

Go to Step 7

Go to Step 10

7

Replace the sun load temperature sensor.

Is the replacement complete?

--

Go to Diagnostic System Check

--

8

Inspect for an open in CKT 552 (BLK) .

Did you find an open?

--

Go to Step 9

Go to Step 11

9

Repair the open in CKT 552 (BLK) .

Is the repair complete?

--

Go to Diagnostic System Check

--

10

Clear any electronic climate control module DTCs.

Does the DTC reset?

--

Go to Step 11

Go to Intermittents and Poor Connections Diagnosis in Wiring Systems

11

Replace the electronic climate control module.

Is the replacement complete?

--

Go to Diagnostic System Check

--

12

Measure the voltage on terminal A of sun load temperature sensor connector to ground.

Is the voltage within the specified range?

4-6 V

Go to Step 5

Go to Step 13

13

Inspect for an open in CKT 590 (LT BLU).

Did you find an open?

--

Go to Step 14

Go to Step 11

14

Repair the open in CKT 590 (LT BLU).

Is the repair complete?

--

Go to Diagnostic System Check

--