ABS dash light on

[grainhauler08]

what makes the ABS light stay on along with my trac. control light. Just came on the other day not any kind of bad road conditions to cause this,just came on. I was thinking that maybe I need to adjust up my brakes,could this have a cause for the lights to come on. I have an 01' IH 9400I . Also what is the button on my dash labeled(Diag. ) and hows this work?

[Jumbo]

You may have a bad wheel sensor or maybe a broken wire. The switch marked "Diag" is for getting fault codes if the check engine light comes on.

[bob h]

what makes the ABS light stay on along with my trac. control light. Just came on the other day not any kind of bad road conditions to cause this,just came on. I was thinking that maybe I need to adjust up my brakes,could this have a cause for the lights to come on. I have an 01' IH 9400I . Also what is the button on my dash labeled(Diag. ) and hows this work?

The abs fault code needs to be checked to determine the problem. Adjusting the foundation brakes will NOT turn the abs light off.

The DIAG switched is used to flash engine fault codes.

[grainhauler08]

I checked wiring over couldn't find any broken wires but could be a sensor. What ABS code? My ABS light was on but no code any where.

[allan5oh]

First, you need to know how to get ABS codes out of the computer. This will tell you what's going on. More then likely it is a rear axle.

From there, go to that axle and swap the wiring side to side(put right side wiring on left sensor, and left sensor on right side wiring). This will tell you if it's the wiring or the sensor. If it's the sensor, the code will switch from left side to right side, or vice versa. If it's wiring, the code will not change. Make sure to pay attention to "active" or "stored" codes.

ABS units are usually behind the transmission somewhere. You may have to change the wiring all the way from there right to the plug for the sensor. It is a good idea to use quality light cord wire(good to -65, nice and flexible!). It's not cheap but it will outlast the truck if installed correctly.

Good luck.

[Kranky]

Since all this snow & cold has been happening around here, we have had a couple instances of the ABS wire going to the sensor on one of the front wheels breaking off. I would suspect that slush & ice is buiding up on the wire making it heavy and breaking it off.

Double check the wiring coming from the wheel speed sensors, that would be the most likely place that a problem would occur.

Also keep in mind that during the time that the dash lights are indicating a fault with ABS & Trac, the ABS & Traction control systems are inoperative.

[boneebone]

Could be a bad sensor or a improperly positioned sensor not reading the tone ring.

[Shnerdly]

It's not uncommon for the ABS light to come on with many trucks. Sometimes it's just dirt or rust particles on the exciter ring inside the drum. If it stays on for more then a day or two then it's probably a bad sensor or wire. The ABS computers don't fail too often.

[Larry227]

Most of the time it's a sensor or the wiring for the sensor. Since it's an IH it's probably a Bendix system. If all the wiring looks ok then you pretty much need to pull the codes to pinpoint it. There are a couple things you can check though. You can unplug the sensors and check them with a multi-meter. A good sensor should have a steady reading of between 900-2500ohms.
Don't forget to check the ABS fuse.
Have you had a wheel seal replaced recently? A lot of times when a hub is pulled if the sensor isn't re-adjusted it will throw an air gap code after it's put back together.
Some ABS faults are as simple to find as testing a sensor or checking a fuse and I've had others that took hours if it was a bad wire in the middle of the harness.

[grainhauler08]

Thanks everyone,It has been bad as far as weather and roads are concerned,probably slush frozen on a sensor or wire and broke. I never knew had a abs fuse,will check that out. If its something else will have to go until warms up,don't have abs on trailer and never use trac control so not really going to bother me much except the freaking lights. I wish I knew how to pull codes,this is new to me. I never got a book with this truck,thought maybe that would help me on alot of things i don't know,if the book gives much info.

[pdm]

If its a Bendix system the ecu should be on top of the rear relay valve. There will be LED lights on the side to indicate where the problem is. The fault codes can be reset by holding a magnet next to the lights for 20- 30 seconds.

If its a Rockwell/Meritor there may be a blink code switch somehwere, near the diagnostic connector? Hold the switch for 1 sec & release & it will blink out a 2 digit code. Hold it for more than 3 sec to clear the codes. Light will blink fast 8 times to indicate codes were cleared, The light will stay on till the truck is driven more than about 4 mph .

maybe try googling bendix abs, meritor abs

[grainhauler08]

ECU relay and where is this? and where does this stuff light up at? by pushing switch what does this do to light things up and hopefully the switch works. Totally confused.

[bob h]

If its a Bendix system the ecu should be on top of the rear relay valve. There will be LED lights on the side to indicate where the problem is. The fault codes can be reset by holding a magnet next to the lights for 20- 30 seconds.

If its a Rockwell/Meritor there may be a blink code switch somehwere, near the diagnostic connector? Hold the switch for 1 sec & release & it will blink out a 2 digit code. Hold it for more than 3 sec to clear the codes. Light will blink fast 8 times to indicate codes were cleared, The light will stay on till the truck is driven more than about 4 mph .

maybe try googling bendix abs, meritor abs

Bendix has been "off and on" with those indicator lights; the ec-16 used them, the ec-17 didn't for example. ...so, I wouldn't look too hard for them. If they ARE used on the ECU, they are; green to indicate power, and a series of 3 red lights to identify the fault.

However, in an '01 9400, my fading memory tells me that the ECU will be found inside the cab, behind the driver's side kick panel (to the left of the clutch pedal), and it's not even easy to locate once that panel is removed; BTDT. There will be a small, round twist-type ?black? connector (maybe 12-wire?) that passes out through the firewall just in front of the driver's feet... I would first remove that connector (from the outside) and inspect for green death.

There is not much point in resistance testing the sensors unless you know which one to check; I would use allan's "sensor connector swap" idea to narrow it down if the firewall connector checks ok.

[Larry227]

You didn't happen to get a phone installed recently did you? Just joking. Today I worked on a 2000 Mack that had an ABS light on. Driver said it started after he had a phone installed. Pulled the codes and it just showed a short to ground on right rear sensor. Harness from sensor to firewall connector tested good. Went inside and saw where they mounted some type of booster or something for the phone. It was screwed onto the metal panel under the right side of the dash. Pulled the panel to continue tracing wires from the firewall and found the Wabco ECU on the backside of the panel. You guessed it. The phone installer put a self tapping screw right through the panel and into the back side of the ABS ECU and shorted out the circuit board. New ECU is 985.00. Driver wasn't happy and I"m pretty sure who will get the next call on his new phone. The MACK VCU module was right next to it and it had a screw through the back of it also but it didn't go deep enough to hit the circuit board.

[grainhauler08]

I better see if my trucker neighbor can help me out on this.No didn't install a phone recently but if I had probably would have found the problem quicker. Me and that guy with the screw gun would have some serious talking to do! The nasty cold winter weather here is probably the cause of the problem,wash the ol" girl up and see what I can find. Sure alot I don't know about this truck wish I had a manual to explain and show me where this stuff is.