Pinout Values and Diagnostic Parameters
ECU Pin Voltage Testing
AIR CONDITIONING SYSTEM
FAULT FINDING
WARNING: The microprocessor is an extremely sensitive and expensive unit, and should only be tested using a digital multimeter with no less than a 3.5 digit display and a resistance of no less than 2 megaohms. Any other form of multimeter will irreversibly damage the microprocessor.
Note: Always allow time for the servo motors and blower motors to come to a rest before starting a check.
The car should be in a workshop and the ambient temperature should be stable e.g 24°C (75°F) for at least 30 minutes before commencing the automatic check.
At 24°C the sensor voltage is 2.972 mV ± 2 mV. The rate of change is 10mV per 1°C. Unless stated otherwise, all checks are carried out at the ECM test plugs
Signal Pin No Voltage
MODE SWITCH: OFF IGNITION SWITCH: AUX 2
Battery supply 1 11 to 14V
Recirc input 9 2 to 6V
Earth/ground 2 0 to 40mV
Earth/ground 6 0 to 40mV
Earth/ground 10 0 to 40mV
Earth/ground 38 0 to 40mV
Earth/ground 45 0 to 40mV
From mode switch 44 0 to 12V
To mode switch 12 10 to 13.3V
MODE SWITCH: (MANUAL) LOW
Low input 13 150 to 350mV
Clutch output - Evap
sensor below 2.72V 20 0.6V
Clutch output - Evap
sensor above 2.72V 20 11.4V
Medium input 14 3 to 5V
High input 15 3 to 5V
Defrost 27 3 to 5V
From ON/OFF Sw. 44 10.3 to 13.3V
Output 43 4.73 to 5.2V
Recirc. output 3 0 to 200mV
HS Relays 16 0 to 200mV
Water valve solenoid 17 0 to 200mV
Centre vent solenoid 18 0 to 200mV
MODE SWITCH: (MANUAL) MEDIUM
Low input 13 3 to 5V
Medium input 14 150 to 350mV
High input 15 3 to 5V
Defrost 27 3 to 5V
MODE SWITCH: (MANUAL) HIGH. SERVO MOTORS: STATIONARY
Low input 13 3 to 5V
Medium input 14 3 to 5V
High input 15 150 to 350mV
Defrost input 27 3 to 5V
MODE SWITCH: (MANUAL) DEFROST
Low input 13 3 to 5V
Medium input 14 3 to 5V
High input 15 3 to 5V
Defrost input 27 150 to 350mV
MODE SWITCH: (MANUAL)
Face level Maximum 28 2.665 to 3.105V
Face level Minimum 28 0 to 200mV
MODE SWITCH: (MANUAL).
Temp. Maximum demand 35 4.75 to 5.25V
Temp. Minimum demand 35 0 to 200mV
MODE SWITCH: (AUTO) TEMPERATURE DEMAND SWITCH: MID-RANGE
Servo motor lower flap 37 0 to 2.0V
Servo motor lower flap 41 0 to 2.0V
Servo motor upper flap 40 0 to 2.0V
Servo motor upper flap 42 0 to 2.0V
MODE SWITCH: (AUTO) TEMPERATURE DEMAND SWITCH: HIGH
Servo motor lower flap 37 7.0 to 9.5V
Servo motor lower flap 41 7.0 to 9.5V
Servo motor upper flap 40 7.0 to 9.5V
Servo motor upper flap 42 7.0 to 9.5V
MODE SWITCH: (AUTO) TEMPERATURE DEMAND SWITCH: MID-RANGE
Recirc. input 9 3 to 5V
Recirc. output 3 0 to 500mV
Reference voltage 7 2.875 to 2.895V
Defrost output 11 0 to 500mV
High speed relays 16 0 to 500mV
Lower feedback pot.. 29 0.6 to 0.9V
Upper feedback pot. 30 1.15 to 1.45V
Water temp.switch engine cold 21 260 to 460mV
Water temp.switch engine hot 21 4.5 to 5.5V
Defrost output 11 0 to 500mV
Clutch output - evaporator
above 2.745 V 20 10.3 to 13.3V
RH Blower feedback 33 10 to 13V
LH Blower feedback 22 10 to 13V
RH Blower control 32 0 to 0.5V
LH Blower control 31 0 to 0.5V
Water valve solenoid 17 0 to 500mV
Centre vent solenoid 18 0 to 500mV
MODE SWITCH: (AUTO) LOW. TEMPERATURE DEMAND SWITCH: MINIMUM
Face Level to mid-range 28 1.43 to 1.45V
SERVO MOTORS STOPPED
Servo motor lower flap 37 0 to 40mV
Servo motor lower flap 41 0 to 40mV
Servo motor upper flap 40 0 to 40mV
Servo motor upper flap 42 0 to 40mV
Lower feedback pot. 29 0 to 0.2V
Upper feedback pot. 30 0 to 0.2V
MODE SWITCH:(AUTO) LOW. TEMPERATURE DEMAND SWITCH :MID-POS.
Temperature demand 35 1.43 to 1.45V
SERVO MOTORS STOPPED
Servo motor lower flap 37 0 to 40mV
Servo motor lower flap 41 0 to 40mV
Servo motor upper flap 40 0 to 40mV
Servo motor upper flap 42 0 to 40mV
Lower feedback pot. 29 0.57 to 0.87V
Upper feedback pot. 30 0.6 to 0.9V
MODE SWITCH:(AUTO) LOW. TEMPERATURE DEMAND SWITCH:MAX.
Temp demand 35 2.665 to 3.105V
Lower flap feedback pot. 29 0.979 to 1.279V
Upper flap feedback pot. 30 1.18 to 1.9V
MODE SWITCH:(AUTO). FACE LEVEL: MAXIMUM
Differential temp. 28 2.665 to 3.105V
Lower flap feedback pot. 29 0.979 to 1.279V
Upper flap feedback pot. 30 1.340 to 1.640V
BLOWER MOTOR TEST
FACE LEVEL: MINIMUM. TEMPERATURE DEMAND SWITCH: MINIMUM
Differential temp. 28 0 to 200mV
Temperature demand 35 0 to 200mV
Note: Allow the servo motors to come to rest before checking voltage levels. Typical figures are given in brackets.
MODE SWITCH RH CONTROL LH CONTROL RH FEEDBACK LH FEEDBACK
Position Pin No.32 Pin No.31 Pin No.33 Pin No.22
Low 1-2V (1.77V) 1-2V (1.77V) 4-6V (5.8V) 4-6V (5.63V)
Med 2-3V (2.28V) 2-3V (2.27V) 3-5V (3.7V) 3-5V (3.4V)
High 1-2V (1.17V) 1-2V (1.19V) 1-2V (1.22V) 1-2V (1.27V)
SET FACE DIFFERENTIAL POT. TO MID POINT
MODE SWITCH RH CONTROL LH CONTROL RH FEEDBACK LH FEEDBACK
Position Pin No.32 Pin No.31 Pin No.33 Pin No.22
Low 1-2V (1.24V) 1-2V (1.27V) 6.5-9V (8.7V) 6.5-9V (8.7V)
Med 1-2V (1.4V) 1-2V (1.4V) 6.9-9V (7.5V) 6.5-9V (7.5V)
High 2-3V (2.2V) 2-3V (2.2V) 3-5V (4.1V) 3-5V (4.0V)
SET FACE DIFFERENTIAL POTTO MAXIMUM
MODE SWITCH RH CONTROL LH CONTROL RH FEEDBACK LH FEEDBACK
Position Pin No.32 Pin No.31 Pin No.33 Pin No.22
Low 1-2V (1.67V) 1-2V (1.63V) 6.5-9V (6.25) 6.5-9V (6.1V)
Med 2-3V (2.17) 2-3V (2.1V) 3-5V (4.25V) 3-5V (4.2V)
High 2-3V (2.3V) 2-3V (2.2V) 3-5V (3.7V) 3-5V (3.5V)
OPEN WATER TEMPERATURE SWITCH LEADS
SET TEMPERATURE DEMAND SWITCH TO MID-POINT
Pin 35 1.43 - 1.45V
RH Servo control Pin 32 0 - 0.5V
LH Servo control Pin 31 0 - 0.5V
SHORT WATER TEMPERATURE SWITCH LEADS MODE SWITCH: Low
Clutch output Pin 20 9.3 - 12.3V
RH Servo control Pin 32 1 - 2V
LH Servo control Pin 31 1 - 2V
Set diff to minimum Pin 28 0 - 200mV
Set temp demand to minimum Pin 35 0 - 200mV
Recirc. output Pin 3 9.3 - 12.3V
High speed relays Pin 16 0 - 200mV
Water valve solenoid Pin 17 9.3 - 12.3V
Centre vent solenoid Pin 18 9.3 - 12.3V
Defrost output Pin 27 0 - 500mV
MODE SWITCH: DEFROST Pin 27 150 - 350mV
High speed relays Pin 16 9.3 - 12.3V
Lower feedback pot. Pin 29 2.709 - 3.100V
Upper feedback pot. Pin 30 1.714 - 2.014V
MODE SWITCH: OFF
Pin 44 0 - 1V
Recirc. output Pin 3 9.3 - 12.3V