B1204 Air Mix Potentiometer Open (Low) - Automotive Repair Guides & Equipment

COMPONENT LOCATION

GENERAL DESCRIPTION

The Air mix actuator(Temperature actuator) located at heater unit. It contains temp motor that changes temp door position and potentiometer that monitors position of temp door. The Air mix actuator(Temperature actuator) regulates the temperature by the procedure as follows. Signal from control unit adjusts position of temp door by operating temp motor and then temperature will be regulated by the hot/cold air ratio decided by position of temp door. In operation, potentiometer delivers temp door position transformed into voltage value to A/C ECU.

DTC DESCRIPTION

The Airconditioner Control Module sets DTC B1204 if the Feed Back signal of Passenger Air mix actuator(Temperature actuator) has been detected open or below 0.1V for 0.3 seconds.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible Cause

DTC Strategy

Voltage check

1.	Poor connection of connected part

2.	Open in signal circuit (Feedback circuit), Power circuit or Ground Circuit

3.	Faulty passenger air mix actuator

4.	Faulty A/C control unit

Enable Conditions

IG KEY ON

Threshold value

Feedback signal has been detected open or below 0.1V for 0.3 seconds

Failsafe

setting temperature : 16°C(62.6°F)-24°C(76.1°F) fix at max. cooling position

setting temperature : 25°C(77°F)-31°C(89.6°F) fix at max. heating position

SPECIFICATION

※ Voltage value of Air Mix potentiometer as a function of temp door position.

Door position	Voltage
Max. cool	0.3±0.15V
Max. warm	4.7±0.15V

DIAGNOSTIC CIRCUIT DIAGRAM

MONITOR SCANTOOL DATA

■ Check Actuation Test

1.	Connect scantool with diagnostic connector.

2.	Warm up the engine to normal temperature after engine start

3.	Select “Air Mix Door Potentiometer-Passenger” parameter on the current data with scantool.

4.	Perform Actuation Test for “Passenger Air Mix Door – 0% / 50% / 100%.

With performing Actuation test, check that the value of Air Mix Door Potentiometer is changed and close to the value of Actuation Test.

Check that the value of Air Mix Door Potentiometer at current data should be close to the value of the actuation test .

Does the value of current data follow in accordance with the each actuation test ?

	▶ This is a intermittent problem caused by poor contact of component or Control Unit. ▶ Thoroughly check the looseness, poor connection, bent, corrosion, contamination, deformation or damage of connector. ▶ Repair or replace as necessary
	▶ Go to ” Inspection/Repair ” procedure.

TERMINAL AND CONNECTOR INSPECTION

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

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

Has a problem been found?

	▶ Repair as necessary.
	▶ Go to “W/Harness Inspection” procedure.

SIGNAL CIRCUIT INSPECTION

■ Check for open in harness

1.	Ignition “OFF”

2.	Disconnect passenger air mix actuator and A/C control unit main harness connector.

Measure resistance between Signal(F/B) terminal of passenger air mix actuator harness connector and Signal(F/B) terminal of A/C-ECU harness connector.

below 1Ω

Is the measured resistance within specification?

	▶ Go to “Check short to ground in harness” as follows.
	▶ Check for open in harness. ▶ Repair as necessary.

■ Check short to ground in harness

1.	Ignition “OFF”

2.	Disconnect passenger air mix actuator and A/C control unit main harness connector.

Measure resistance between Signal(F/B) terminal of passenger air mix actuator harness connector and chassis ground .

Infinity

Is the measured resistance within specification?

	▶ Go to “Power circuit Inspection” procedure.
	▶ Check for short to ground in control harness. ▶ Repair as necessary.

POWER CIRCUIT INSPECTION

■ Check power in harness

1.	Ignition “OFF”

2.	Disconnect passenger air mix actuator and Connect A/C control unit main harness connector.

3.	Ignition “ON”

Measure voltage between Sensor REF(5V) terminal of passenger air mix actuator harness connector and chassis ground .

approx. 5V

Is the measured voltage within specification?

	▶ Go to “Ground circuit Inspection” procedure.
	▶ Check for open and short to ground in harness. ▶ Repair as necessary

GROUND CIRCUIT INSPECTION

■ Check for open in harness

1.	Ignition “OFF”

2.	Disconnect passenger air mix actuator and A/C control unit main harness connector.

Measure resistance between Sensor ground(-) terminal of passenger air mix actuator harness connector and Sensor ground(-) terminal of A/C-ECU harness connector.

below 1Ω

Is the measured resistance within specification?

	▶ Go to ” Component inspection” procedure .
	▶ Check for open in harness. ▶ Repair as necessary

COMPONENT INSPECTION

■ Check passenger air mix actuator

1.	Ignition “OFF”

2.	Disconnect passenger air mix actuator and connect A/C control unit main harness connector.

3.	Connect (+) terminal of battery to WARM(+) of passenger air mix actuator and (-) terminal to COOL(-). (Component side)

4.	Verify that the Air mix actuator(Temperature actuator) operates to the WARM position.

Verify that the Air mix actuator(Temperature actuator) operates to the COOL position with reverse connecting. ( COOL(+) and WARM(-) ). (Component side)

Refer the specifications in Fig.1)

Fig.1)

Actuator harness	WARM(+)	COOL(-)	Door position
Battery terminal	12 V	ground	Max.warm
Battery terminal	ground	12 V	Max.cool

Fig.1) ※ Function of the actuator motor according to terminal connection type. (observe safety regulations)

Is “Door position” display near the specified value?

	▶ Go to “Check potentiometer” procedure.
	▶ Substitute with a known-good passenger air mix actuator and check for proper operation. If the problem is corrected, replace passenger air mix actuator

■ Check potentiometer

1.	Ignition “OFF”

2.	Connect passenger air mix actuator and A/C control unit main harness connector.

3.	Ignition “ON”

Measure voltage between Signal(F/B) terminal of passenger air mix actuator harness connector and Sensor ground(-) terminal of A/C-ECU harness connector. (Component side)

Refer the specifications in Fig.2)

Fig.2)

Door position	Voltage
Max. cool	0.3±0.15V
Max. warm	4.7±0.15V

Fig.2) ※ Voltage value of Air Mix potentiometer as a function of temp door position.

Is “voltage” display near the specified value?

	▶ 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.
	▶ Substitute with a known-good passenger air mix actuator and check for proper operation. If the problem is corrected, replace passenger air mix actuator

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