Mechanics

ABS LIGHT ON, MOTOR ON ABS SYSTEM RUN AF

1996 Jeep Cherokee

Brakes problem
1996 Jeep Cherokee 6 cyl Four Wheel Drive Automatic 160000 miles

The small " booster" motor on the ABS system continues to run even after the engine is off. It ran all night last night and drained my battery. In my repair manual it says to check the fuses, and get the trouble code read. My problem is now that the battery is dead I am stuck with having it towed somewhere and I am afraid that once I get it to a shop I will be stuck there and have to pay for whatever repairs they want to impose upon me. I would like to get an idea of what the problem could be before walking into a shop. Thank you to whomever takes the time to help my with the problem.
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Tylarinyosemite
October 31, 2008.



First, charge or replace the battery, if you cant read the codes, remove the ABS fuse, the brakes will work without the ABS sytem, you can drive it like this until you decide to fix it.
ANTI-LOCK BRAKE SYSTEM -1996 Jeep Cherokee Classic
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OPERATION
The Teves Mark IVG Anti-Lock Brake System (ABS) ABS modulates brake fluid apply pressure during high pedal pressure and high vehicle deceleration to prevent wheel lock-up. Wheel lock-up does not mean wheel has stopped, but wheel is turning slower than other wheels.
Hydraulic Control Unit (HCU) consists of a valve body with a pump body, pump motor and accumulators attached. Accumulators store extra fluid released to system for ABS mode operation. Pump/motor provides fluid volume needed and is operated by a DC type motor. Pump/motor is controlled by Controller Anti-Lock Brake (CAB). Valve body contains CAB controlled solenoid valves that modulate brake pressure during ABS operation.
When ignition is switched on, CAB performs a static system initialization. When vehicle speed reaches approximately 6 MPH, CAB briefly cycles pump to verify operation. HCU solenoids are checked continuously. If a Diagnostic Trouble Code (DTC) is detected during system initialization, Amber ABS warning light will be activated and a DTC will be stored in CAB memory.
When ABS is activated, vibrations and/or pulsations may be felt in brake pedal. Pump/motor and solenoid valve cycling may be heard. Some wheel slip is required for best braking performance. This wheel slip may be heard as tire chirping. DO NOT confuse tire chirping with tire skidding. Braking on rough road surfaces can cause wheel hop. CAB may detect wheel hop as a lock-up condition, causing ABS system to activate.

NOTE: For more information on brake system, see the BRAKE SYSTEM article.

10/31/2008

Merlin2021
Oct 31, 2008.
OK, I have removed the ABS fuses, and drove it around for a while. Thanks for the tip. This will help me while I decide what to do.

I have called 3 different repair shops asking what might cause the electric pump motor to continue running, Brake masters said it was more than likely an electrical problem and to go have the codes read. Midas said the relay was more than likely sticking and that they would charge $90 to scan for the code(s). And another local repair shop said it was most likely either the pump motor being shorted out or that the relay was sticking. These shops also told me that this would cost around $1300 to repair, is this a fair estimate?

Auto zone used to scan codes for free but apparently about a month ago the state of California made them stop doing this. Now all they can do is sell the scanners and they are non-refundable. Is there any place to perhaps get the codes scanned for cheaper than $80-$100? Thanks again!

Tiny
Tylarinyosemite
Oct 31, 2008.
The scanners sold by Autozone will not read " C" codes, these are what ABS codes are. I wll tell you it is the CAB as noted above, the solinoid is sticking, but it's built into the CAB. I junkyard may be a good place to get one. But scan for codes BEFORE you spend any money!

Merlin2021
Oct 31, 2008.