B1318

CIRCUIT DESCRIPTION

The sun load sensor is a light sensitive photodiode that controls signal voltage to the heater and A/C programmer. This photodiode is different from standard thermistor sensors and 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. Signal voltage will vary between 5V (open circuit) and 0V (short circuit).

TEST CONDITION(S)

1. Ignition ON.

ACTION TAKEN

1. A substitute reading of 250 counts will be implemented to allow continued operation of the system.

TEST DESCRIPTION

1. Scan tool displays sun load sensor reading. jumping the harness connector determines if the wiring or sensor is the cause.

NOTES ON INTERMITTENCE

If an intermittent DTC B1318 is being set connect scan tool, and select data list, open/shorts data and note reading.

Manipulate the wiring while observing scan tool.
If failure is induced, the reading will jump. Check for poor terminal contact, and an obstructed or defective sensor.