GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 DTC 🢒 DTC B1318 Sunload Sensor Open Circuit

Object Number: 506748 Size: MF
HVAC Components
Cell 68: Temperature Sensors
Handling ESD Sensitive Parts Notice
Power Distribution Schematics
Power Distribution Schematics
HVAC Compressor Control Schematics

Circuit Description

The sun load sensor is a light sensitive photodiode that controls the signal voltage to the heater and A/C programmer. This photodiode is different from the standard thermistor sensors. The resistance measurements will not produce accurate results. The heater and A/C programmer monitors the voltage on CKT 590 to the sensor. When the sensor is in direct light, the heater and A/C programmer reads a low voltage at pin C7. As the sensor becomes shaded, the signal voltage increases. The signal voltage varies between 5 V (open circuit) and 0 V (short circuit).

Conditions for Running the DTC

Turn the ignition to the ON position.

Action Taken When the DTC Sets

A substitute temperature reading of 250 counts is implemented in order to continue the operation of the system. There will be no automatic compensation due to sunload.

Notes On Intermittence

If an intermittent DTC B1318 is set, use a Scan Tool and select the following settings:

    • Data list
    • Open/shorts data
    • Observe the reading

Manipulate the wiring while observing the Scan Tool . If a failure is induced, the reading will jump. Inspect for the following conditions:

    • Faulty terminal contact
    • An obstructed or defective sensor

Test Description

  1. Perform the Diagnostic System Check before continuing with the diagnosis of this DTC.

  1. The Scan Tool displays the sun load sensor reading. Jumping the harness connector determines if the wiring or the sensor is the cause.

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 to the ON position.
  2. Connect a Scan Tool .
  3. Disconnect the sunload sensor.
  4. Attach a jumper between terminals A and B. Refer to Using Fused Jumper Wires in Wiring Systems.

Did the DTC change from B1318 to B1319?

--

Go to Step 4

Go to Step 3

3

Measure the voltage at terminal B. Refer to Using Fused Jumper Wires in Wiring Systems.

Is the voltage approximately equal to the specified value?

5 V

Go to Step 6

Go to Step 5

4
  1. Replace the sunload sensor. Refer to Sun Load Sensor Replacement .
  2. Use the Scan Tool in order to clear the codes.

Did you complete the repair?

--

Go to Diagnostic System Check

--

5

Measure the voltage at terminal C7. Refer to Measuring Voltage in Wiring Systems.

Is the voltage approximately equal to the specified value?

5 V

Go to Step 8

Go to Step 7

6
  1. Repair the open CKT 407 between terminal B and S217. Refer to Wiring Repairs in Wiring Systems.
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

7
  1. Inspect the terminal contact. Refer to Testing for Electrical Intermittents in Wiring Systems.
  2. If the contact is OK, replace the heater and A/C programmer. Refer to Programmer Replacement .
  3. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

8

Measure the voltage at cavity E of connector 203. Refer to Measuring Voltage in Wiring Systems.

Is the voltage approximately equal to the specified value?

5 V

Go to Step 10

Go to Step 9

9
  1. Repair the open in CKT 590 between the heater and A/C programmer and connector 203. Refer to Wiring Repairs in Wiring Systems.
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--

10
  1. Repair the open in CKT 590 between connector 203 and the sensor. Refer to Wiring Repairs in Wiring Systems.
  2. Use the Scan Tool in order to clear the code.

Did you complete the repair?

--

Go to Diagnostic System Check

--