wondering if someone can guide me please. I’m gonna try to diagnose
When I turn key on or start my trailer abs doesn’t show up on dash and abs light on trailer doesn’t blink like it’s supposed to.
Do I just test every connection with a volt meter with key on or do I have to start the truck ?
Any other steps I can take ?
Trailer abs light doesn’t come up on dash
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Greggg, Oct 19, 2019.
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Light bulb bad?
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No I still checked but the “trailer abs” doesn’t even come on and go off when o turn the truck on either so my abs ecu isn’t getting power somehow. I’m thinking just running new wire if I have trouble isolating the problem.
Just wondering if there are any tips or something I should look for. I’m no mechanic or electrical guy unfortunately. -
Is this a truck, or trailer problem?
Class 8 truck?Rideandrepair Thanks this. -
Well,from my understanding, if the Trailer has a light, it doesn’t send the signal to the Trucks light on dash. My Trailer abs wasn’t working.it wouldn’t come on with key. ( normal test mode) . I had to replace tha main power cord. It went from a plug near the Left side rail, to the abs module. Once it was replaced, light stayed on, then did blink code diagnosis, and replaced a wire from module to sensor. So starting at module testing supply wire for power, working your way back towards, and including ( if necessary) the pigtail, and to fuse box. ( if necessary). I’m terrible with electrical, if I could figure it out, so can you.
Intothesunset Thanks this. -
Just a note, If I remember correctly, the blue wire in pigtail receptacle supplies the power to Trailer abs. Only the newer trailers without a yellow abs light at left rear, send a signal to the dash.
Intothesunset Thanks this. -
Did you test with key on or engine running ? if it gives me too much trouble I might just run a new wire from the pigtail back to where it’s getting voltage, if that’s the case.
Rideandrepair Thanks this. -
Check with key on. Blue has constant power. abstroubleshooting.com has Wabco codes. Although mine had been spliced together by Penske, before I bought it. It’s against DOT rules to splice abs wires, from what I’ve read.
Working2party Thanks this. -
First Question on trailer ABS is where either Truck or Trailer built on or before July 1, 1997? Older units are not required to have ABS.
Next Question is was either unit built before 2000? Older units did not require the truck to have a working ABS light. Or in other words truck to trailer communications weren’t required.
If both are newer than the dates above, turn Key on (engine off) and listen for ABS modulator clicks on truck and trailer (lights on trailer should come on at this time) . This checks that the Blue Constant (key power) Wire has power. (Center pin of ABS cord)
If there are no clicks at the trailer. Press the brake pedal and again listen for the clicks, (this time they may “chuff”) and make sure the trailer brake lights come on. This checks that the Red brake light wire circuit is getting power. (Opposite of the 7way cord Ground pin) If it fails this test then you need to look for a grounding issue.Rideandrepair Thanks this. -
Rideandrepair Thanks this.
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