VERACRUZ(EN) >2009 > G 3.8 DOHC > Heating,Ventilation, Air Conditioning > Troubleshooting>B1208 Intake Potentiometer Open (Low)  
Component Location

General Description
Intake door located at heater unit controls the inlet of car. It contains intake motor that changes intake door position and potentiometer that monitors position of intake door. When driver operates the intake switch, ECU receives mode signal from intake switch and operates intake door motot to turn intake door to intended positiony. (with FRE mode signal, intake door is closed and with REC mode signal, intake door is opened)In operation, potentiometer delivers intake door position transformed into voltage value to A/C ECU .
DTC Description
The ECM sets DTC B1208 if there is an open circuit or poor connection in the Intake actuator signal harness
DTC Detecting Condition
Item
Detecting Condition
Possible Cause
DTC Strategy
Voltage check
Poor connection of connected part
Open circuit in signal/power harness
Short circuit in signal/power harness
Faulty Intake potentiometer
Threshold value
< 0.1V
Detecting time
0.3sec
FAIL SAFE
Setting mode : REC Fix at REC position
Setting mode : Except REC Fix at FRE position

Signal Waveform And Data
※ Voltage value of Air Mix potentiometer as a function of temp door position.
Door position
Voltage
Error Detecting Condition
FRE
0.3±0.15V
Undervoltage : 0.08V or less
REC
4.7±0.15V
Overvoltage : 4.9V or more

Schematic Diagram

Monitor Dtc Status
1.
Connect scantool to Data Link Connector(DLC).
2.
Warm up the engine to normal operating temperature.
3.
Monitor DTC(Diagnostics Trouble Code) on the scantool.

4.
Is the same DTC displayed again?

▶ Go to " Inspection/Repair " procedure .

▶ Fault is intermittent caused by poor contact in the sensor's and/or A/C-ECM connector or was repaired and A/C-ECM memory was not cleared. Thoroughly check connectors for looseness, poorconnection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of vehicle Repair" procedure.

W/harness 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.
3.
Has a problem been found?

▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure

▶ Go to "Signal circuit Open Inspection" procedure.

Signal Circuit Open InspectioN
1.
Ignition "OFF"
2.
A/C-ECU, Intake actuator : Disconnect.
3.
Measure resistance between Signal(F/B) terminal of Intake actuator harness connector and Signal(F/B) terminal of A/C-ECU harness connector.

Specification : 1Ω below

4.
Is "resistance" display near the specified value?

▶ Go to "Signal circuit Ground short Inspection" procedure.

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

Signal Circuit Ground Short Inspection
1.
Ignition "OFF"
2.
A/C-ECU : Connect, Intake actuator : Disconnect.
3.
Measure resistance between Signal(F/B) terminal of Intake actuator harness connector and and chassis ground .

Specification : Infinity

4.
Is "resistance" display near the specified value?

▶ Go to "Power circuit Open Inspection " procedure.

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

Power Circuit Ground Short Inspection
1.
Ignition "OFF"
2.
A/C-ECU, Intake actuator : Disconnect.
3.
Measure resistance between Sensor REF(5V) terminal of Intake actuator harness connector and Sensor REF(5V) terminal of A/C-ECU harness connector.

Specification : 1Ω below

4.
Is "resistance" display near the specified value?

▶ Go to "Power circuit Inspection" procedure.

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

Power Circuit Inspection
1.
Ignition "OFF"
2.
A/C-ECU : Connect, Intake actuator : Disconnect.
3.
Ignition "ON"(ENGINE "OFF").
4.
Measure voltage between Sensor REF(5V) terminal of Intake actuator harness connector and and chassis ground .

Specification : approx. 5V

5.
Is "voltage" display near the specified value?

▶ Go to "Sensor ground circuit Open Inspection " procedure.

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

Component Inspection
Check Intake actuator
1.
Ignition "OFF"
2.
A/C-ECU, Intake actuator : Disconnect.
3.
Connect (+) terminal of battery to FRE(+) of intake actuator and (-) terminal to REC(-) .(Component side)
4.
Verify that the actuator operates to the REC position
5.
Verify that the temperature actuator operates to the FRE position with reverse connecting.( REC(-) and FRE(+)) (Component side)

Specification : Refer the specifications in fig.1

Actuator harness
WARM(+)
COOL(-)
Door position
Battery terminal
12 V
ground
FRE
ground
12 V
REC

※ Function of the actuator motor according to terminal connection type. (observe safety regulations)
6.
Is "Door position" display near the specified value?

▶ Go to "Check potentiometer" procedure.

▶ Substitute with a known-good Intake actuator and check for proper operation. If the problem is corrected, replace Intake actuator and then go to "Verification of Vehicle Repair" procedure.

Check potentiometer
1.
Ignition "OFF"
2.
A/C-ECU : Connect, Intake actuator : Disconnect.
3.
Ignition "ON"(ENGINE "OFF").
4.
Measure voltage between Signal(F/B) terminal of Intake actuator harness connector and and chassis ground .(Component side)

Specification : Refer the specifications in fig.2

Door position
Voltage
Error Detecting Condition
FRE
0.3±0.15V
Undervoltage : 0.08V or less
REC
4.7±0.15V
Overvoltage : 4.9V or more

Specifications : Voltage value of intake potentiometer as a function of intake door position.
5.
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 Intake actuator and check for proper operation. If the problem is corrected, replace Intake actuator and then go to "Verification of Vehicle Repair" procedure.

Verification Of Vehicle Repair
After a repair, it is essential to verifying that the fault has been corrected.
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2.
Using scantool, Clear DTC.
3.
Operate the vehicle within DTC Enable conditions in General information.
4.
Are any DTCs present?

▶ Go to the applicable troubleshooting procedure.

▶ System is performing to specification at this time.