GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 DeVille 🢒 DTC 🢒 DTC B1318 Sunload Sensor Open Circuit

Object Number: 315450 Size: LF
HVAC Components
Cell 68: Temperature Sensors
Handling ESD Sensitive Parts Notice
Cell 10: COMFORT Fuse
Cell 10: COMFORT Fuse
(Cell 67 (2 of 2))

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 signal voltage at pin C7. As the sensor becomes shaded, the signal voltage increases and voltage is pulled through sensor ground. 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 Intermittents

If an intermittent DTC B1318 is set, use a Scan Tool in order to 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:

    • A poor 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 the Scan Tool .
  3. Disconnect the sensor. Attach a jumper between the terminals.

Did the DTC change from B1318 to B1319?

--

Go to Step 4

Go to Step 3

3

Measure the voltage at terminal B.

Is the measure voltage approximately equal to the specified value?

5  V

Go to Step 6

Go to Step 5

4
  1. Replace the sensor. Refer to Sun Load Sensor Replacement
  2. Using theScan Tool clear the codes.

Is the repair complete?

--

Go to Diagnostic System Check

--

5

Measure the voltage at terminal C7.

Is the measured 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 A and S217.
  2. Using theScan Tool clear the code.

the repair complete?

--

Go to Diagnostic System Check

--

7
  1. Inspect the terminal contact.
  2. If OK, replace the heater and A/C programmer. Refer to Programmer Replacement
  3. Using theScan Tool clear the code.

--

Go to Diagnostic System Check

--

8

Measure the voltage at cavity E of connector 203.

Is the measure 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.
  2. Using theScan Tool clear the code.

Is the repair complete?

--

Go to Diagnostic System Check

--

10
  1. Repair the open in CKT 590 between connector 203 and the sensor.
  2. Using theScan Tool clear the code.

Is the repair complete?

--

Go to Diagnostic System Check

--