ABS/Brake Light

[fastdel]

i have a 2001 3500 cummins that for some reason the ABS and Brake light came on a couple days ago.
used the key check to look at codes and i show no codes at all. any suggestions as to what could be causing this?

 

[DavidC]

2 wd, 4 wd ?. speedometer ok ?

 

[fastdel]

2 wd, 4 wd ?. speedometer ok ?

4wd dually speedometer is fine. there are no symptoms other than some unrelated power issues i need to address soon as well.
i did replace a broken LF abs sensor about 300 miles ago and reset codes at that time. the lights came back on about 100 miles ago.

 

[DavidC]

It is usually a front sensor. I believe they ohm around 600 across the 2 pins. You could also have a wiring issue near the wheels. If it was the rear you would have speedometer issues also. I would ohm both front ones, a bad sensor usually or a rock may have done some modifications.

 

[Road Dog]

Most code readers scan the ECM and PCM only. You need a reader that can access the ABS module. The ABS light will come on if your brake fluid is low so check that too.

 

[fastdel]

checked brake fluid and checked resistance on LF front sensor 1024ohms. had ABS checked with tester and showed no error codes.
brake and abs light still on. i have ordered a new sensor and will try connecting it without installing to see if that will make any difference.
will update once i have checked that out.

 

[DavidC]

Thanks

 

[Curtis Johnson]

Thanks

 

[Curtis Johnson]

Sorry, I’m mildly retarded. Anyway, it’s probably your speed sensor on the rear diff. It doesn’t always mess with your speedometer. I replaced mine a month ago with an eBay unit and it is now turning on same two lights again. No problem with speedo though.

 

[fastdel]

Well I checked the RF sensor and it showed open resistance so i replaced it. The rear sensor showed 1020ohm resistance (about the same as the new LF sensor. found i was a little low on PS fluid so i topped it off, then checked every connector under the hood. now when i start up the light goes off. if i sit still it will stay off, but as soon as i drive a couple hundred feet both ABS and Brake light comes on again. it is looking like i may have to pony up and send this thing to the dealer after all.

 

[DavidC]

I had an issue once. Startup and get to 40mph the abs/brake light would come on, the only way to reset was shut the truck off and restart, then the same routine hit 40 and lights on. As a last resort I unplugged the trailer hitch on the back of the plug. No more lights. I dielectric greased the cavity of the plug and no more issues.

 

[DavidC]

FYI, my 99 rear sensor ohm's around 1800.

 

[Timd32]

Anyway the clock spring could be part of this?

Not sure if that will just cause a intermittent ABS light only with no brake light.

The not coming on till rolling a bit down the road would think it's not the clock spring. Just throwing it out there.

 

[Road Dog]

checked brake fluid and checked resistance on LF front sensor 1024ohms. had ABS checked with tester and showed no error codes.
brake and abs light still on.

You need a better tester. The lights turn on when there are fault codes.

I had an ABS issue in a 1500 (rear wheel ABS). The limited slip clutch pack came apart, chipped several teeth on the tone ring and caused a "erratic ABS signal fault". All it took was a new carrier to fix the problem. That fault showed up after driving a while and reset every time I started the truck.

 

[GAmes]

I followed the troubleshooting procedure in the FSM and found one of the harness connectors behind the left front tire was full of water.

 

[KATOOM]

When my ABS/Brake light was illuminated it was the brake light switch under the dash. Easy fix.

 

[fastdel]

well i broke down and took it to dealer who condemned the abs controller. i have sent it off for rebuild and will update as soon as it comes back

 

[GAmes]

When mine failed I unplugged it. No more lights and money in my pocket.

 

[NIsaacs]

When mine failed I unplugged it. No more lights and money in my pocket.

On an '01, the ABS module also controls the speedometer and cruise control. On my '91, I did the same thing, just unplugged it, all is good.

 

[GAmes]

When I swapped over to the G56 I tapped the ABS sensor in the differential to power the speedometer through a Dakota Digital SGI-5. It was easy to bypass the module, one splice.