Many malfunctions in the electrical system are caused by poor connection. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration,or damage.

Has a problem been found?

	▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
	▶ Go to "W/Harness Inspection" procedure.

Ignition "OFF"

Disconnect Auto Defog sensor and Connect A/C control unit main harness connector.

Ignition "ON"

Measure voltage between Power terminal of Auto Defog sensor harness connector and chassis ground.

Is the measured voltage within specification?

	▶ Go to " Ground circuit Inspection " procedure .
	▶ Check for open and short to ground in harness & A/C control unit. ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure.

Ignition "OFF"

Disconnect Auto Defog sensor and A/C control unit main harness connector.

Measure resistance between Sensor ground terminal of Auto Defog sensor harness connector and chassis ground.

Is the measured resistance within specification?

	▶ Go to "Check for open in harness" as follows.
	▶ Check for short to open in control harness. ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure.

Ignition "ON"

Connect Auto Defog sensor and A/C control unit main harness connector.

Measure signal waveform between Defog Sck terminal of Auto Defog sensor harness connector and chassis ground.(M)1

Measure signal waveform between Defog Sck terminal of Auto Defog sensor harness connector and chassis ground.(M)2

Measure signal waveform between Defog Sck terminal of Auto Defog sensor harness connector and chassis ground.(M)3

Fig.1) M)1

Fig.2) M)2

Fig.3) M)3

Is the measured value within specifications?

	▶ Check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
	▶ Go to Next procedure.

Ignition "OFF"

Disconnect Auto Defog sensor and A/C control unit main harness connector.

Measure resistance between Defog Temp terminal of Auto Defog sensor harness connector and chassis ground.

Measure resistance between Defog Sck terminal of Auto Defog sensor harness connector and chassis ground.

Measure resistance between Defog Data terminal of Auto Defog sensor harness connector and chassis ground.

Is the measured resistance within specification?

	▶ Go to Next procedure.
	▶ Check for short to ground in control harness. ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure.

Ignition "OFF"

Disconnect Auto Defog sensor and Connect A/C control unit main harness connector.

Ignition "ON"

Measure voltage between Defog Temp terminal of Auto Defog sensor harness connector and chassis ground .

Measure voltage between Defog Sck terminal of Auto Defog sensor harness connector and chassis ground .

Measure voltage between Defog Data terminal of Auto Defog sensor harness connector and chassis ground .

Is the measured voltage within specification?

	▶ Go to Next procedure.
	▶ Check for short to battery in harness. ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure.

Ignition "OFF"

Disconnect Auto Defog sensor and A/C control unit main harness connector.

Measure resistance between Defog Temp terminal of Auto Defog sensor harness connector and Defog Temp terminal of A/C-ECU harness connector.

Measure resistance between Defog Sck terminal of Auto Defog sensor harness connector and Defog Sck terminal of A/C-ECU harness connector.

Measure resistance between Defog Data terminal of Auto Defog sensor harness connector and Defog Data terminal of A/C-ECU harness connector.

Is the measured resistance within specification?

	▶ Substitute with a known-good Auto Defog sensor and check for proper operation. If the problem is corrected, replace Auto Defog sensor and then go to "Verification of Vehicle Repair" procedure. ▶ Substitute with a known-good A/C-ECU and check for proper operation. If the problem is corrected, replace A/C-ECU and then go to "Verification of Vehicle Repair" procedure.
	▶ Check for open in harness. ▶ Repair as necessary and then go to "Verification of Vehicle Repair" procedure.