Where are the brains for ABS?

scooter_scum · **Posted:** Mon Oct 12, 2009 11:00 am

Well, I love my Liberty CRD. Bought it used and still working out the kinks from the previous owner. I discovered the Cruise Control did not work. Took it to the Dealer and the best they could determine was the previous owner did their own wiring harness for the trailer and may have damaged the computer. My MPG is down too. Seems to run rich. My MPG is around 21.5 with mixed highway driving and City driving over 3600 miles. I have had one tank at 24 MPG. All others have been in the 20-22 MPG range.

WE got our first snow in Colorado. Tried the ABS/ESP out on the ice roads and nothing. No warning lights on the dash either. No pulsing when the tires were locked up.

So the general question is, where is the ABS controlled from?

If it is the general ECU, does anybody know where I might find one cheap?

Don't mean to whine. I dearly love this car. The power is amazing. I guess I like my cars like my women .... high maintenance

BBB · **Posted:** Mon Oct 12, 2009 1:04 pm

The ABS controller is located on the ABS power/ pump unit in the engine compartment. You will see the multi-wire connector to the lower right of the ABS unit if your looking at it from the drivers side over the fender. Ours lost the ability to communicate so we've been driving with standard brakes and the ABS light for a while now. Interestingly the ABS unit tried to run the ABS pump on occasion when braking so I pulled the ABS pump fuse to take it off line until I replace the complete ABS unit. Note: If replaced the ABS power unit/ controller HAS to be bleed at the dealer with the correct computerized tool. :roll:

e_poirier2004 · **Posted:** Mon Oct 12, 2009 7:36 pm

I also have a good one. Sometimes, the pedal goes slowly down when pressed firmly. Then I activate the abs by driving hard and braking hard and the pedal becomes hard again. Any idea what it might be? By the way, the master cylinder has been changed, 3 calipers, all rotors, all pads and liners and all the system bled and flushed. That's a good one!!!

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The brake booster uses vacuum from the engine to provide assist. The diesel makes less vacuum than a gasoline engine. A gasser has natural vacuum in the intake, while the diesel uses an internal vacuum pump. The vacuum produced is tied to engine rpm, so the booster assist recovery can take a few seconds to build back up after pushing the brakes hard. This is normal, but if you have a vacuum leak somewhere, the hard pedal will be more pronounced and take longer to recover.

RabidRdKill · **Posted:** Tue Oct 13, 2009 9:12 pm

Do the ABS telltale and ESP event telltale (car w/ squiggly lines) light up during the bulb check at vehicle startup? Does the ESP lamp light up when you turn off the system using the ESP OFF button on top of the steering column? If so then the ECU is at least alive and talking.

If the ESP module is dead you should get the lamp on the cluster as BBB described. The lamp is turned on by the CCN if there is a lack of messaging from the ESP module - In addition to it getting a message from the module if there are faults.

scooter_scum · **Posted:** Tue Oct 13, 2009 11:03 pm

There are no warning lights. Initial diagnoses is a rear wheel sensor needed to be replace. Let's hope this is it.

You guys rock!!

scooter_scum · **Posted:** Wed Oct 21, 2009 7:58 pm

Well, they finally found all the problems. Not one. Not two, but 4 sections of wire that were broken. Unreal!!

$550 later, all my options now work!! ABS, Cruise control, etc. Whew!

BBB · **Posted:** Sun Oct 25, 2009 10:49 pm

Did they give any indication where the 4 wires were broke so I can check mine?

By the way, all should check the 1" wire harness loom that goes behind the alternator bracket. Mine was worn thru the aluminum over rap tape and black plastic loom into the wire insulation due to sharp casting flashing left on the alternator bracket when it was produced. Filing the flashing and a loom re-wrap stopped that potential issue before it hit copper.

:idea:

We should get a thread/ sticky/ tech list of all the places folks find shorted and/ or broken wires on the CRD :wink:

Where are the brains for ABS?

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