ABS powering up question

Normally when you forst turn your key on, pretty much all your dash lights come on, then go out. The others that stay on usually turn off after the engine has been started.
If you've replaced the sensor wire, ... is it the proper distance away from the pick up!?

Cheers,

 

ABS light must be on for 2 seconds according ECE/DOT laws. It is lamp test.

If ABS light stays on - u have ABS fault code active.

Ok, how to read and reset ABS codes? U need to identify system first.

Ways of identification: look for unit and read unit part #.
What truck? what year?

 

Your trailer ABS lamp should come on for 2-3 seconds, then go out. You will hear the solenoids clicking as it runs through it's self check, if they do not go through the self check with the key on, check voltage at the blue wire. I've found many with corrosion giving enough power to activate the ECU and light, but as soon as it powers a solenoid for a self check, voltage is pull below 9v which isn't enought to power the ECU anymore.

It sounds like your system may be working OK though, you need a 2nd person to turn on the key while you're in the back to listen for the clicks. With brake pressure, you hear the chuffs, but with the key only no serice brakes wont chuff, they only click much quieter.

You don't have to clear codes if you don't want to, they will stay in there and show inactive. I personally clear all codes once it's fixed so there is no confusion if there is another problem. You don't want a mechanic wasting time diagnosing old codes.

Also keep in mind that most systems hold the ABS light on after a fault was repaired until it senses wheel speed. If you fix something and the light stays on, drive 5-7 mph and it will go out if it's fixed. Once it senses a fault, it needs to go through a full self check to clear the lamp, which means sensing wheel speed.

 

The ABS system is powered by the center post on your 7 way. If that power source fails, the secondary source is the brake light wire. If the system activates and does the system check (ABS light flashes) every time you hit the brakes, you need to check the primary power supply. If you have power at the 7 way center pin, check the trailer mounted 7 way box. If there isn't power to the center pin coming off the tractor, check your fuses.

 

Ive got an iteresting problem...
Original haldex plc-plus 1m+ miles, commands abs light on, no codes.
Drive it 5-7 mph, light doesnt go off. Check again, no codes. So i replace the module (because i have one)...
Now, ABS light on (full time), flashes codes on my Haldex info center so quickly, you cant read them and there is no control of the menu buttons on the info center.