Electric Load Sensor: Testing and Inspection

Electrical load signals (component "ON") are sent to the ECU from the headlight switch, blower motor switch and cooling fan switch.

HEADLIGHT SWITCH

Headlight switch signal can be checked at ECU terminal 1U. With headlights "ON," terminal voltage should be approximately 12V. With headlights "OFF," voltage should be approximately 0V. If headlight operation is okay but terminal voltage is always approximately 0V, check for short or open circuit in wiring from headlight relay to ECU terminal 1U.

BLOWER MOTOR SWITCH

Blower motor switch signal can be checked at ECU terminal 1S, ignition "ON." With blower switch "OFF" or in low position, terminal voltage should be approximately 12V. With switch "ON" in mid, high or super high position, voltage should be approximately 0V. If blower motor operation is okay but terminal voltage is always approximately 0V, check for short in wiring from blower switch to ECU terminal 1S, bad connection at ECU connector or ECU malfunction. If blower motor operation is okay but terminal voltage is always approximately 12V, check for open circuit in wiring from blower switch to ECU terminal 1S.

COOLING FAN SWITCH

Cooling fan switch signal can be checked at ECU terminal 1R with engine running. With fan operating or diagnosis connector terminal TFA grounded, terminal voltage should be approximately 0V. With engine idling and fan "OFF," terminal voltage should be approximately 12V. If cooling fan operation is okay but terminal voltage is always approximately 0V, check for open or short circuit in wiring from fan relay to ECU terminal 1R or ECU malfunction.