Piston Slap: (ABS) Lights, Scanner, Action

by Sajeev Mehta

June 3rd, 2009 10:03 AM

TTAC Commentator Kericf asks:

I have a 1998 Isuzu Rodeo 4×4 with the ABS light starting to come on intermittently. The first time it happened I thought I heard a clicking noise under the dash like a bad solenoid. I had to replace the solenoid for my turn signals once and it made a similar noise when they would go haywire. A lot of forums on the Rodeos point to bad speed sensor on the rear axle, but if it’s just a bad solenoid that would be easier. The truck has 214,786 miles as of this email and I am wondering if I should also worry about rubber brake lines deteriorating. I can’t find any leaks but I don’t want to blow a brake line in Houston traffic.

Sajeev answers:

First and foremost, check your rubber brake lines for cracking or collapsing. Even if you pay a mechanic for their trained eyes, that’s still cheap insurance. Then again, our Houston freeways have more than adequate shoulder room for an emergency run off.

More often than not, an illuminated ABS light is from a computer generated trouble code. You must, must, MUST check for this code before replacing anything on the system.

If you’re lucky, you can borrow the correct scan tool from a parts store ($100-ish deposit on your credit card) and pull the code yourself, for free. If not, expect to pay the standard diagnostic fee at a local shop.

Get the code and Google it for a diagnosis. I’m not a gambling man, but I’d bet on the speed sensor too: that’s a very common wear item on ABS systems. If accessible, clean the sensor and ring with a can of brake cleaner to remove any debris on its magnetic parts. That probably isn’t your problem, but it never hurts to first try a free fix.

As far as the clicking noise under the dash, it’s probably not ABS related [NB: I have never touched an Isuzu’s braking system] because most of the system is normally self-contained under the hood, including the wiring and modules.

[Send your technical queries to mehta@ttac.com]

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2 of 13 comments

T-truck on Jun 04, 2009

My 1995 Rodeo has had the same problem for the decade that I have owned it. The ABS light blinks when ever I hit a bump on the road. I guess I could have spend thousands a replacement sensor, but why really? The brakes seem to work fine despite the intermittent light.

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Rpn453 on Jun 05, 2009

Check all the ABS wiring you can get at. My mother's car had an intermittent ABS light which eventually became constant. I found a broken wire right at the speed sensor. Easy fix.

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