ON-BOARD DIAGNOSTIC SYSTEM


BHE070261190T03

Malfunction Detection Function

• Detects errors in the input and output signals. (The ignition switch is at the ON position or the engine is operating.)

• If a malfunction is detected, a DTC is output to the information display through the malfunction display function. At the same time, malfunction detection results are sent to the fail-safe and memory functions.

Fail-safe Function

• If a malfunction is detected by the malfunction detection function and a malfunction is determined, the following controls are performed to prevent mis-operation of the full-auto air conditioner and malfunction of output parts.

Fail-safe Function Table

Malfunction determination part

When malfunction is determined at IG SW ON

When IG SW is turned to ON during malfunction

Cabin temperature sensor
Cabin temperature sensor input value is set at 25 °C {77 °F}.
Ambient temperature sensor
Ambient temperature sensor input value is set at the value just before the malfunction.
Evaporator temperature sensor
Evaporator temperature sensor input value is set at 0 °C {32 °F}.
Solar radiation sensor
Solar radiation sensor set value is set at 0 W/m2.
ECT sensor
ECT sensor input value is set at 80 °C {176 °F}.
Air mix actuator
(Potentiometer)
Stops the air mix actuator drive signal at the point a malfunction is determined.
However, MAX COLD when the manually set temperatures is at 18.0, and MAX HOT when the manually set temperature is 32.0.
Airflow mode actuator
(Potentiometer)
Stops the mode actuator drive signal at the point a malfunction is determined.
However, for manual operation with the airflow mode selector switch, only vent mode is operable.
Defroster switch operation is operable
Air mix actuator
(Motor lock)
Stops the air mix actuator drive signal at the point a malfunction is determined. Then a drive signal is output to the air mix actuator for approx. every 5 min and malfunction determination is performed.
After the IG SW is at ON, regular output of the air mix actuator drive signal recommences. Then a drive signal is output to the air mix actuator approx. every 5 min and malfunction determination is performed.
Airflow mode actuator
(Motor lock)
Stops mode actuator drive signal at the point a malfunction is determined. Then a drive signal is output to the mode actuator approx. every 5 min and malfunction determination is performed.
After the IG SW is at ON, regular output of the mode actuator drive signal recommences. Then a drive signal is output to the mode actuator approx. every 5 min and malfunction determination is performed.

Memory Function

• Stores the signal determined to be malfunctioning by the malfunction detection function, and the memory cannot be cleared even if the ignition switch is at the LOCK position or the malfunction has been repaired.

• To clear stored malfunction information, press the climate control unit AUTO switch and the REC/FRESH switch simultaneously during past malfunction display mode.

Malfunction Display Function

• Function for outputting present or past malfunctions to the information display as DTCs.

• DTCs are output by turning the ignition switch to the ON position while simultaneously pressing both the A/C switch and the REC/FRESH switch for 3 s or more.

• Redundant DTCs are output with lower-numbered DTC numbers.

DTC Display Example

1
Example: DTC 02
2
Information display

Present Malfunction Display Mode

• Presently occuring malfunctions (open/short circuit) are detected and the DTCs are indicated on the information display.

DTC TABLE

-: Not applicable

No.

Output pattern

Malfunction Location

Detection Condition

Memory Function

02

Solar radiation sensor (present malfunction)
Solar radiation sensor circuit short
 
06

Cabin temperature sensor (present malfunction)
Cabin temperature sensor circuit open/short circuit
 
10

Evaporator temperature sensor (present malfunction)
Evaporator temperature sensor circuit open/short circuit
 
12

Ambient temperature sensor (present malfunction)
Ambient temperature sensor circuit open/short circuit
 
14

ECT sensor (present malfunction)
ECT sensor circuit open/short circuit
 
18

Air mix actuator (potentiometer) (present malfunction)
Air mix actuator (potentiometer) circuit open/short circuit
 
21

Airflow mode actuator (potentiometer) (present malfunction)
Airflow mode actuator (potentiometer) circuit open/short circuit
 

Past Malfunction Display Mode

• Past occurence of sensor and other input circuit malfunctions (open/short circuit) are stored and the DTCs indicated in the table are displayed on the information display. Once a past malfunction has been stored and after the malfunctioning part has been repaired, the past malfunction will continue to remain in the memory. Therefore, after repairing, clear the past malfunction from the memory.

• To clear stored past malfunction information, press the climate control unit AUTO switch and the REC/FRESH switch simultaneously during past malfunction display mode.

DTC TABLE

X: Applied

No.

Output pattern

Malfunction Location

Detection Condition

Memory Function

07

Cabin temperature sensor (past malfunction)
When an open/short circuit has occured in the cabin temperature sensor circuit 1 time or more in the past.
X
11

Evaporator temperature sensor (past malfunction)
When an open/short circuit has occured in the evaporator temperature sensor circuit 1 time or more in the past.
X
13

Ambient temperature sensor (past malfunction)
When an open/short circuit has occured in the ambient temperature sensor circuit 1 time or more in the past.
X
15

ECT sensor (past malfunction)
When an open/short circuit has occured in the ECT sensor circuit 1 time or more in the past.
X
19

Air mix actuator (potentiometer) (past malfunction)
When an open/short circuit has occured in the air mix actuator (potentiometer) temperature sensor circuit 1 time or more in the past.
X
22

Airflow mode actuator (potentiometer) (past malfunction)
When an open/short circuit has occured in the airflow mode actuator (potentiometer) temperature sensor circuit 1 time or more in the past.
X
58

Air mix actuator (motor lock) (past malfunction)
When motor lock has occured in the air mix actuator circuit 1 time or more in the past.
X
59

Airflow mode actuator (motor lock) (past malfunction)
When motor lock has occured in the airflow mode actuator circuit 1 time or more in the past.
X

A/C Operation Check Mode

• The A/C amplifier forces operation of output related moving parts according to the operation check table regardless of the input, while simultaneously displaying changes on the information display that match the A/C amplifier control as well as performing automatic illumination of each switch indicator light. Each transition is verified whether it is as according to the operation check table through visual inspection, listening to operation sound or placing the hand on the blow-off opening to determine a malfunction.

Operation Check Table

Step

Target part

Operation condition

Monitor display*

1
Blower motor

1
2
Air mix door

20.0 (0 %)
20.5 (50 %)
21.0 (100 %)
20.5 (50 %)
3
Airflow mode door

3
4
Air intake door
A/C compressor
FRESH⇔REC
ON⇔OFF
4

* :
Shown on the information display (at the set temperature display) according to each step.