Code C1232 left front open or short

Tiny
ABEAUCHOT
  • MEMBER
  • 1998 OLDSMOBILE INTRIGUE
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 223,000 MILES
I'm having trouble with a proper diagnosis. I have a c1232 code left front sensor open or short. I have gained access to the brake module and have measured AC voltage from both the left and right sensor. So I know that signal is getting to the module. Also the resistance at the left sensor is 1k ohms. So it seems that all my tests check out, that's why I replaced the module. However I'm still getting left front open or short c1232. As soon as I clear the code it immediately pops back up again. At this point I'm baffled at why I cannot diagnose the problem. I have changed this hub I believe around 2010-11. But again its producing an AC voltage, has a resistant of 1k ohms and the signal is measurable at the pigtail harness to the brake module. What could be the problem?

Thanks,

Adam
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Saturday, March 30th, 2019 AT 2:20 PM

7 Replies

Tiny
CARADIODOC
  • EXPERT
Did you measure the resistance from either sensor wire to ground?

I can get you started with a few comments of value. The first is these GM front-wheel-drive cars are notorious for many repeat failures due to the normal play that develops in the front wheel bearings. The dealer's scrap metal bins are full of these. (By the way, the old ones will work just fine on cars without ABS). Those sensors develop real wimpy signals to start with, then, when a little normal play develops in the bearings, the tone ring moves away from the sensor far enough to reduce the signal strength even more, to the point the computer can't read it. Movement between parts is always a requirement, so since the signal strength goes down as road speed decreases, this usually results in false activation at low speeds. It is real common for a new bearing assembly to cause the same problem after as little as 15,000 miles.

Next, you can't use a digital voltmeter to read these signals. The AC Volts range is only accurate with a 60 hertz sine wave. These sensors develop a square-wave signal at a much higher frequency. If you have a "Frequency" range on your meter, you are likely to get a reading, but that won't tell you if it's high enough in voltage to be read by the computer. The best we can do is use a scanner to view live data and see what the computer is seeing.

Since you are obviously not a do-it-yourselfer, there is one more thing I've heard multiple times in training classes. There was a software glitch with some scanners that only pertained to some '90s GM vehicles. It would confuse the front left and right sensors. I can't remember if it set a fault code for the wrong wheel, or if the square wave signals were switched on the graphing display. You might try performing the resistance tests on the other wheels. 1,000 ohms could be okay, but when I've measured these sensors, it's more common to find around 400 - 800 ohms. The point is you don't have an open circuit.
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Sunday, March 31st, 2019 AT 12:19 AM
Tiny
ABEAUCHOT
  • MEMBER
I tested short to ground on the front left side. And I am getting a measurement on both wires to ground. One was around 450 ohms the other wire was over 1,000 ohms. So I think now it's a positive diagnosis on a bad hub assembly? The front right side has no continuity on the short to ground test on either of the two wires.
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Tuesday, April 2nd, 2019 AT 2:11 PM
Tiny
CARADIODOC
  • EXPERT
Unplug the left front wheel speed sensor, then measure those two wires again. The better suspect is a wire is rubbed through and grounding to the body. There could also be corrosion between two adjacent terminals in a connector.

If the short is on one of the wires, you'll read it on the other wire too by reading through the sensor. That second reading will be higher by the amount of resistance in the sensor. When you unplug the sensor, the short will still be read on a grounded wire, but you'll find infinite resistance on the other one.

If it is indeed a shorted sensor, both wires at the computer will read infinite resistance when the sensor is unplugged. If you find that, to verify the sensor is what is shorted, just measure from ground to the two terminals in the sensor's plug.
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Tuesday, April 2nd, 2019 AT 4:38 PM
Tiny
ABEAUCHOT
  • MEMBER
It did turn out to be the hub assembly. I replaced some of the wiring that was typically prone to failure and still had a short to ground. After installing the new hub assembly all is well and fixed. Thanks for all the help.
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Friday, April 5th, 2019 AT 1:00 PM
Tiny
CARADIODOC
  • EXPERT
Dandy. I find that hard to believe, but I say that just about every week.

What you might consider, if you're a pack rat like I am, is to save a few sensors so you don't have to buy a whole new bearing assembly. In fact, we found that bearing for GM cars is a lot more expensive when you buy it without the sensor. When the car doesn't have anti-lock brakes, buy the less-expensive bearing with the sensor, then just don't plug it in, or tap it off to save it.

Happy to hear you solved it.
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Friday, April 5th, 2019 AT 4:42 PM
Tiny
ABEAUCHOT
  • MEMBER
Thanks again for the advice and help. I had changed this bearing in 2017. A AutoZone Duralast dl513121. I cut the wires at the sensor and measured a short to ground. 500 ohms and 1500 ohms on each wire. Somewhere on the internal winding it developed a short. It only had 15,000 miles on it. Very disappointed that it didn't last longer.
Best regards,
Abeauchot
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Friday, April 5th, 2019 AT 4:51 PM
Tiny
KEN
  • ADMIN
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help.
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Monday, April 8th, 2019 AT 6:42 PM

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