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EBS Trailer Testing With ISOCheck

What Is The ISO EBS Truck & Trailer Lead

How does the EBS truck & trailer Susie lead work?

Everyone seems to have there own ideas how it works, ranging from; "if it’s not plugged in your trailer brakes wont work", & "it’s only a back up power anyway"

Both are incorrect!

The truth is...

The Electronic Braking System (EBS) Susie or the ISO 7638 (its correct name) is essential for the trailers Electronic Braking System (EBS) to operate correctly.

So, if a truck has an ISO7638 socket a tractor and trailer must be connected with an ISO7638 Susie and the EBS must be working correctly!

Also this means the EBS warning light the truck operator should be checking is in the cab and not the one on the trailer headboard (if there is one).
This is where the problems start, how does the EBS lead actually work, well this is how:
Pin 1 in most trucks is permanent live
Pin 2 is switched ignition live
Pin 3 is common return to battery negative
Pin 4 is common return to battery negative
Pin 5 is the warning light control (positive)
Pin 6 is “CAN” High
pIn 7 is “CAN” Low

Pin 5 which is the warning light control wire, this pin seems to be continually misunderstood. Some people think pin 5 is controlled by the trucks EBS system or even by the truck itself, both of these are incorrect, how it works is quite simple, a basic explanation is detailed below:

Power from the truck battery routes to a fuse, then to the ignition switch and then to the warning light in the dash board, finally then to pin 5 in the socket.

When an EBS Susie ISO7638 lead is connected to the trailer the trailer EBS system sees 24 volts down pin 5, which and then reduces that voltage inside the trailer ECU to below 5 volts (earth) which then activates the EBS light on in the truck cab.

Once a truck & trailer is in motion and the the trailer EBS system is happy with the wheel speed signals, the ecu then raises the voltage back up to 24 volts and the warning light in the cab goes out, if a fault appears when a truck & trailer is on the road, the ecu lowers the voltage again activating the In Cab Warning Light.(Please Note This Is a Basic Description).

An easy way to test the truck & trailer ISO Connection socket is the ISOCheck

Truck ISO Tester

This simple to use tester will diagnose any pin fault in seconds, just plug it in and within 10 seconds a full pin test will identify and pin faults and by flashing the red LED’s according to which pin is faulty, example 4 flashes, pin 4 faulty.

Most new trucks don’t actually have a warning light as such, Instead the dash is an LCD display which shows a picture of a trailer or trailer warning but pin 5 still works the same way,
It’s always controlled by the trailers ECU.

Furthermore pin 6 and 7 are utalised within an EBS Susie Lead, these are the “CAN” connections “CAN” means "control area network" which in simple terms is a connection between two or more ECU's allowing information to pass back and forth.
With an EBS truck and an EBS trailer the braking is done through the “CAN” lines, when the truck brake is pressed the truck sends a “CAN” signal to the trailer ECU to tell the brakes to apply, if the “CAN” signal fails the brakes will still work via the air pressure signal through the service line.

Some seem to think that if an ABS truckis connected to an EBS trailer then the trailer brakes will not work properly, this is not the case as the truck can't send the “CAN” signal to the trailer then the trailer brakes will work as normal via the air pressure.

The ISOCheck can also be used continuously between a truck unit and trailer as a constant visual aide.

To purchase the ISOCheck product range via our online PayPal shop - Click On Purchase ISOCheck Now!

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