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Post by Greg K on Nov 19, 2023 16:58:34 GMT -6
I love, love, love my 1997 bright-white diamond Autobahn with Acoustimass Bose and sunroof -- but its fickle ABS system is trying our relationship!
I've hooked up my voltmeter and spun each wheel, and I'm getting a signal from each wheel.
I've pulled each tire and cleaned each ABS connection, and checked the resistance: each is testing almost a perfect number.
I've installed a brand-spanking new ABS electronic control module I bought on eBay.
Yet still those gosh-darn (original expletive unsuitable for public consumption) ABS and Traction Control lights won't go out.
I'm wondering if the 'exciter' ring on the wheel bearing may be worn or bad in a spot or two?
And praying that the costly ABS pump unit is isn't glitchy; although regular braking is fine. I haven't been able to access its electrical plug yet to give connections a good cleaning.
Looks like I'm going to have to buy an ABS-capable code scanner; neither of the ones I have will do my ABS system.
QUESTION: Do any of you have any suggestions I might still try short of buying a scanner? (Up here in Edmonton, Canada, I can't think of any auto part stores that will scan for me, and I don't know any friends who have one, sigh....)
Or perhaps one of you have bought a really cheap scanner that can do ABS and one that you're really happy with and can recommend?
Thanks, as always, for any thoughts you can share,
Greg "Dr K" Kennedy
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Post by Marc on Nov 19, 2023 17:19:20 GMT -6
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Post by Greg K on Nov 19, 2023 17:26:29 GMT -6
Thanks Marc for the suggestion!
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Post by Marc on Nov 19, 2023 17:43:21 GMT -6
Thanks Marc for the suggestion! OK! I hope it works out. |
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Post by AuroraGirlFromMars on Nov 19, 2023 19:05:39 GMT -6
I love, love, love my 1997 bright-white diamond Autobahn with Acoustimass Bose and sunroof -- but its fickle ABS system is trying our relationship! I've hooked up my voltmeter and spun each wheel, and I'm getting a signal from each wheel. I've pulled each tire and cleaned each ABS connection, and checked the resistance: each is testing almost a perfect number. I've installed a brand-spanking new ABS electronic control module I bought on eBay. Yet still those gosh-darn (original expletive unsuitable for public consumption) ABS and Traction Control lights won't go out. I'm wondering if the 'exciter' ring on the wheel bearing may be worn or bad in a spot or two? And praying that the costly ABS pump unit is isn't glitchy; although regular braking is fine. I haven't been able to access its electrical plug yet to give connections a good cleaning. Looks like I'm going to have to buy an ABS-capable code scanner; neither of the ones I have will do my ABS system. QUESTION: Do any of you have any suggestions I might still try short of buying a scanner? (Up here in Edmonton, Canada, I can't think of any auto part stores that will scan for me, and I don't know any friends who have one, sigh....) Or perhaps one of you have bought a really cheap scanner that can do ABS and one that you're really happy with and can recommend? Thanks, as always, for any thoughts you can share, Greg "Dr K" Kennedy The Teves IV ABS system is finicky. Have you checked the fluid level at the abs unit |
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Post by AuroraGirlFromMars on Nov 19, 2023 19:07:26 GMT -6
An amber "ANTILOCK" indicator lamp, located in the instrument panel cluster, operates as follows under normal conditions:
-When ignition switch is turned to "RUN" prior to starting the engine, the "ANTILOCK" lamp comes on for a short period of time, and then goes out.
-As engine is cranked, the red "BRAKE" and amber "ANTILOCK" lamps come on. When the key is returned to the "RUN" position, both lamps will go off. Neither the red "BRAKE" warning lamp or the amber "ANTILOCK" indicator lamp should come on while the vehicle is being driven.
-The "ANTILOCK" lamp will come on also when a malfunction in the ABS is detected by the control module. If only this lamp is on, normal braking is available. However, if both the red "BRAKE" and amber "ANTILOCK" lamps are on during vehicle operation, something might be wrong with the hydraulic brake system.
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Post by AuroraGirlFromMars on Nov 19, 2023 19:09:17 GMT -6
The "BRAKE FLUID" indicator and the low brake fluid input to the instrument cluster are connected to the brake fluid level switch and the ignition switch. The "PARK" indicator is connected to the park brake switch and the ignition switch. The ignition switch "BULB TEST" position does not have a detent, but the ignition switch closes to ground to light the "BRAKE FLUID" and "PARK" indicators before reaching the "START" position.
The master cylinder reservoir brake fluid level switch closes to light the "BRAKE FLUID" indicator, display the "LOW BRAKE FLUID" message on the DIC and briefly sound a fast chime when the brake fluid level in the reservoir is low. This condition may be caused by a leak in one of the brake lines. The engine must be running with the brake fluid level switch closed for approximately 10 seconds before the "LOW BRAKE FLUID" message appears on the DIC. Filling the master cylinder reservoir to its normal level opens the brake fluid level switch contacts. However, make sure to repair the brake system before filling the master cylinder reservoir.
The park brake switch loses when the park brake is applied, lighting the "PARK" indicator and turning on the "PARK BRAKE SET" message on the DIC once the engine has been running for approximately 10 seconds. If the vehicle travels 15 meters (50 feet) with the park brake applied, the Body Control Module (MALL) sounds a chime. Releasing the park brake opens the switch and turns off the "PARK" indicator, turns off the "PARK BRAKE SET" message on the DIC and disables the chime.
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Post by AuroraGirlFromMars on Nov 19, 2023 19:11:47 GMT -6
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Post by Greg K on Nov 19, 2023 21:36:11 GMT -6
Well, AuroraGirl, first of all, thanks so much for the info. You are always on the ball, and so kind to take time for us.
I will say the RED BRAKE LIGHT does not come on, and only shows briefly when starting car, as you indicated, and as it should.
It's the TCS and ABS orange lights that flicker, and stay on.
You mentioned brake fluid level. I will investigate that further, for sure. Does it have a level separate from the regular brake fluid reservoir under the hood?
Greg
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Post by Greg K on Nov 19, 2023 21:41:50 GMT -6
Aurora Girl: How do you check the fluid level at the ABS pump unit?
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Post by Greg K on Nov 20, 2023 0:10:18 GMT -6
Full confession time.
D'OH!!!
Just realized I totally forgot to check 40A and 30A fuses under hood that power ABS pump.
Fingers crossed! 🤞😁
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Post by AuroraGirlFromMars on Nov 20, 2023 5:16:51 GMT -6
Aurora Girl: How do you check the fluid level at the ABS pump unit? there is a small reservoir at the abs unit  at least there should be |
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Post by RCA1186 on Nov 20, 2023 8:56:25 GMT -6
Full confession time. D'OH!!! Just realized I totally forgot to check 40A and 30A fuses under hood that power ABS pump. Fingers crossed! 🤞😁 Any luck? For what it's worth, I've had these lights appear for a few days and go off on their own. Maybe try to get the ABS system to activate to see if it's even functional, in a safe manner of course (think hard brake on a gravel road) |
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Post by Greg K on Nov 20, 2023 23:56:32 GMT -6
No luck yet; fuses were fine under the hood.
Will keep you posted. I'm thinking a twitchy bearing, but can't confirm until I get a scanner.
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Post by Greg K on Nov 26, 2023 22:21:51 GMT -6
I may have isolated the problem to my rear left (driver's side) wheel bearing or the wiring that connects it. Sensor issue.
The resistance is all wrong. Instead of giving me about 1 ohm, it's showing "OL" overload on my tester.
When I had the wheel off, the isolated wheel bearing said the right resistance, but when I test it from the main plug to the abs computer module, it's wrong.
Will pull the wheel again tomorrow and sort this puppy out!
Greg
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Post by Greg K on Nov 26, 2023 22:31:23 GMT -6
With regard to scanners, I wanted to share a warning that while all of them will read the OBD2 engine codes, many of them don't cover the ABS, airbags and more of the fancier features for our Gen I and Gen II Auroras.
I find it's always wise to go to the manufacturer's website and search for "vehicle coverage" or "vehicle compatibility" and see for yourself that the 'extras' like all system scans, bidirectional information, live data and more are indeed functional for our particular models and years.
For example, while the popular Blue Driver plug in module has all kinds of features, it will not do ABS at all for my 97.
Another scanner I almost bought, when I read the fine print online, only does American cars from 2005 and up when it comes to ABS, SIR and more.
In any event, just thought I'd pass this on. These scanners brag up a storm, but many of them have overlooked the Auroras when it comes to the more detailed scanning functions -- which is why we wanted to buy them in the first place.
Frustrating, but now we know!
Greg
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Post by AuroraGirlFromMars on Nov 27, 2023 0:23:34 GMT -6
so you tested the wheel bearing AT the wheel with connector undone, the wheel bearing tested fine on resistance? Testing a wheel bearing you should instead use AC voltage and spin the wheel. if you could find a way to consistently spin the same speed, such as someone turning it or even a drill , you would see a constant voltage. But OL sounds like the wire paths are crossing internally maybe..? But you say it tests wrong at the connector to the ABS unit? To me that points toward the wiring not the wheel bearing. But 1997 auroras had a one year only (or maybe a couple) rear wheel bearing setup.  The one on the right is a 1997. In 1998 GM G and C(park avenue) cars went to a new design rear wheel bearing(left in the picture) The one on the right is dependant on an air gap between the toothed wheel and the sensor pickup. A loose wheel bearing can cause this to be inaccurate and erratic. So if you put the weight on the bearing with the wheel before you tested at the module, that could be why. |
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Post by Greg K on Nov 27, 2023 3:29:36 GMT -6
You make excellent points, Aurora girl! Because the bearing in question did test the correct resistance when I had the wheel off but says open circuit when I test the wiring from the ABS computer back to the wheel has me convinced almost certainly that I just have a bad wire or a bad connection from the bearing to the ABS computer. I will keep my fingers crossed, and it did occur to me too if I only had a way to spin those Wheels at a consistent speed it would be the poor man's way of getting live data if there were a variance in the speed being sent to the computer, which would indicate some wear and tear or breakdown on the Exciter ring or teeth in the bearing or whatever they call that magnetic thing.
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Post by AuroraGirlFromMars on Nov 27, 2023 15:43:53 GMT -6
You make excellent points, Aurora girl! Because the bearing in question did test the correct resistance when I had the wheel off but says open circuit when I test the wiring from the ABS computer back to the wheel has me convinced almost certainly that I just have a bad wire or a bad connection from the bearing to the ABS computer. I will keep my fingers crossed, and it did occur to me too if I only had a way to spin those Wheels at a consistent speed it would be the poor man's way of getting live data if there were a variance in the speed being sent to the computer, which would indicate some wear and tear or breakdown on the Exciter ring or teeth in the bearing or whatever they call that magnetic thing. No the speed wouldnt have to be consistent from wheel to wheel, just consistent to see if it can produce a consistent voltage at the same speed. (ac voltage) |
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Post by Greg K on Nov 27, 2023 16:15:22 GMT -6
 Hi Aurora Girl and Team Aurora: Got outside today and pulled rear driver's side wheel, unplugged ABS sensor/bearing and confirmed resistance (about 1 ohm) and spin test (yes, it generates current) so bearing is good. So then I tested continuity on wires by running a wire from the plug, through my multimeter, and then up the side of the car to the ABS Computer plug under the hood. The white wire is good, the black wire has an open/break somewhere. Once I establish where P100 and P402 connections are, and as fate would have it, it's somewhere under the car or buried in engine compartment, which I cannot reach at the moment, it will be a quick fix. I have the manuals, and am just now looking for the location. (Of course, if my Aurora were up on a hoist, I could do it sooooooo much easier.) Thanks for all your help, and so far so good, Greg "Dr K" |
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Post by Greg K on Nov 27, 2023 19:21:31 GMT -6
 This collection of very important looking plugs are under the rear driver side passenger seat, just ahead of the wheel well. They SURE look like they could use a good blast of contact cleaner. And the middle one looks like it may be the culprit that's preventing my ABS from working. It has a black and white wire, just like the sensor plug on the wheel bearing nearby. Heck, that middle one even looks like it's not seated tightly into its socket, with that gap on the left side. I'm hopeful. Tomorrow, weather permitting, we'll see if we can solve this. That's all for now. |
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Post by Greg K on Nov 28, 2023 19:13:19 GMT -6
 Well, esteemed fellow Auroranauts, my saga of diagnostic pain has ended! It turns out the 2-3 feet of black wire from the rear left wheel sensor/bearing to the junction plug under the rear seat had a break/open somewhere. So I took a length of wire, tapped into the wire near the sensor, and tapped the other end into the wire near the junction plug, then carefully zip-tied it to the original wiring, and voila! When I started m 97 Aurora, the ABS and Traction amber lights went out after 2-3 seconds. This dysfunctionality of my ABS had been bugging me for months, and it doesn't help that I can be obsessive-compulsive at times about having everything working in my car. Once I had the rewiring done, I took my multimeter, set the resistance dial to 2K, and tested the circuit from the main plug at the ABS computer. Perfection. 1 ohm. And I came THIS CLOSE to spending a few hundred bucks on a better scan tool, or a hundred bucks on a new rear bearing. The moral of the story? Always take the time to diagnose thoroughly. Use your GM manual, if you have one, or ask someone here at the club. I'm a happy camper again, till the next fun challenge my 1997 or 2001 Aurora throw my way. Thanks to everyone on this site for your kind guidance. Greg "Dr K" Kennedy |
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Post by AuroraGirlFromMars on Nov 28, 2023 20:18:46 GMT -6
Glad to hear you had found it in the easiest to repair section of the wiring! Im glad those plugs were there to narrow down the area to run a new wire. Fantastic!
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Post by AuroraGirlFromMars on Nov 28, 2023 20:19:24 GMT -6
PS, a tech 2 clone or a tech2win capable device and a computer would go VERY far for a gm car owner and would do every function a dealer could do to your car for you. something to think about
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Post by Greg K on Nov 28, 2023 20:47:57 GMT -6
I will definitely buy one of those high-end devices before spring! I have a couple of more basic scanners, but they don't do ABS, SIR, etc. And I am VERY glad that the bad patch of wire was so easily defined by the junctions at each end, so easily accessible with a hydraulic jack and jack stand. God was kind to an old Aurora fool today  |
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