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Andy
Andy, Truck Diagnostic Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 1586
Experience:  International trucks, International, Maxxforce and Cummins engines, diagnostic, electrical, Hvac and refrigeration repairs
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Last 8 of vin #. Yc083674

Customer Question

Last 8 of vin #. Yc083674
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Andy replied 1 year ago.

There are ten LEDs plus a magnetically actuated reset switch in the controller diagnostic display. The first six LEDs locate the defective condition to a specific area of the vehicle, while the next three indicate the problem component (or its wiring). The LEDs are software driven and either ON or OFF, depending upon their monitor function. The ten LEDs are as follows:

LED FRT

Red LED

LED MID

Red LED*

LED RER

Red LED

LED RHT

Red LED

LED LFT

Red LED

LED TRC

Red LED

LED MOD

Red LED

LED SEN

Red LED

LED ECU

Red LED

LED VLT

Green LED

RESET +

No LED

* This LED is not used for diagnostic purposes. It will, however, light when a magnet is placed on the RESET switch in the diagnostic display

"FRT" (Front) LED
This Red LED illuminates and latches ON to indicate the location of a problem component or its wiring. It will be illuminated at the same time as either the RIGHT or LEFT LEDs and either the MOD or SEN LED.

"MID" (Mid Axle) LED
Only 6x4 vehicles with traction control feature and wheel sensors on all four rear axle wheel ends will use this LED. Standard installations will not include wheel sensors on all four rear wheel ends. On 6x4 vehicles with traction control, the Red LED illuminates and latches ON to indicate the location of a problem with a speed sensor or speed sensor wiring. The MID LED should not illuminate at the same time as the MOD LED .

"RER" (Rear) LED
This Red LED illuminates and latches ON to indicate the location of a problem component or its wiring. It will be illuminated at the same time as either the RHT or LFT LED and either the MOD or SEN LED.

"RHT" (Right) LED
This Red LED illuminates and latches ON to indicate the location of a problem component or its wiring. It will be illuminated at the same time as either the FRT or RER LED and either the MOD or SEN LED.

"LFT" (Left) LED
This Red LED illuminates and latches ON to indicate the location of a problem component or its wiring. It will be illuminated at the same time as either the FRT or RER LED and either the MOD or SEN LED.

"TRC" (Traction) LED
This Red LED illuminates and latches ON indicating a permanent or intermittent problem in the traction control system. It may be illuminated with the MOD LED or by itself.

"MOD" (Modulator) LED
This Red LED illuminates and latches ON to indicate a permanent or intermittent short or open circuit in one of the M-21 modulator valve solenoids or wiring to the solenoids from the controller. There are four M-21 modulator valves, each having two solenoids. This LED should be illuminated at the same time as either the RHT or LFT LED, and either the FRT or RER LED.

"SEN" (Speed Sensor) LED
This Red LED illuminates and latches ON indicating permanent or intermittent failure. The failures that are indicated are:

  1. Open or shorted wheel speed sensor.

  2. Open or shorted wheel speed sensor circuits.

  3. Wheel speed signal not present or is not within expected range (pushed back sensor).

The SEN LED will be illuminated at the same time as either the RHT or LFT LED and either the FRT, MID or RER LED.

"ECU" (Electronic Control Unit) LED
This Red LED illuminates to indicate that the controller itself has failed. It illuminates and latches ON for all controller failures except low voltage. If the controller supply voltage is less than 9 volts DC, the LED illuminates to indicate that the controller is inactive. When the supply voltage goes above 9 volts DC, the LED will turn OFF.

"VLT" (Voltage) LED
This Green LED illuminates and remains ON during vehicle operation to indicate that vehicle power is reaching the controller. If the power supply to the controller from the vehicle electrical system is out of range (below 11 volts or above 17 volts) the Green VLT LED will flash until the power supply returns to the acceptable voltage range.

"RESET"
Under the RESET area of the LED display is a magnetically sensitive switch used to reset the diagnostic system. The device will respond to a magnet sufficient to lift a 3 ounce weight. Holding the magnet against the RESET causes all the LEDs to light while the magnet is against the reset.

Customer: replied 1 year ago.
Can the truck travel safely by removing the relay so that the light turns off. Need to travel a distance to shop.
Expert:  Andy replied 1 year ago.
but I believe the light stays on in the dash anyway . That's fine . You still have brakes . It's just that antilock won't work until the problem is repaired .
Expert:  Andy replied 1 year ago.
Hi there ! Just looking for an update ! Do you still need help ? I see the question is still open ! Let me know !
Please do not forget to rate my answer ! Feedback is important and bonus is appreciated . Thank you !

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