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strange noise AND C1243


davnport

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Mama said something terrible is wrong with her '97 deVille, so I took it for test drive and to get coffee for the AM. Noticed nothing until I backed out of supermarket parking spot when the car shuddered-like while backing. First thought was CV joint as I was turning too, but tried again backing without turning. It feels like something is grabbing hold of something, not constantly, but sort of catch, release, then once again.

Got it back home (nothing noticeable going forward) and dumped the codes, to find only the C1243 code.

Is the noise/shuddering symptomatic of BPMV (whatever that means!) problems or unrelated?

Any education/direction cheerfully accepted.

davnport

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Mama said something terrible is wrong with her '97 deVille, so I took it for test drive and to get coffee for the AM. Noticed nothing until I backed out of supermarket parking spot when the car shuddered-like while backing. First thought was CV joint as I was turning too, but tried again backing without turning. It feels like something is grabbing hold of something, not constantly, but sort of catch, release, then once again.

Sounds like the brakes are being applied for a short period. Your C1243 indicates the BPMV (brake pressure modulator valve) is stalled and I don't know what GM means by stalled. Is that the only code presented?

If it was my car, I would find a suitable section of road or parking lot (wet if possible) and do a series of full panic stops in an attempt to activate ABS action. Alternate with a series of jack rabbit starts to get the traction control system to operate. This might not clear the problem with the modulator valve, but you will not do any damage by trying. It would be best if Mama did not witness this.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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It feels like something is grabbing hold of something, not constantly, but sort of catch, release, then once again.

Sounds like the ABS was activating.

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If the BPMV motor stalled, the ABS fluid circuit is stopped up. Look for a kinked or clogged brake line.

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Mama said something terrible is wrong with her '97 deVille, so I took it for test drive and to get coffee for the AM. Noticed nothing until I backed out of supermarket parking spot when the car shuddered-like while backing. First thought was CV joint as I was turning too, but tried again backing without turning. It feels like something is grabbing hold of something, not constantly, but sort of catch, release, then once again.

Got it back home (nothing noticeable going forward) and dumped the codes, to find only the C1243 code.

Is the noise/shuddering symptomatic of BPMV (whatever that means!) problems or unrelated?

Any education/direction cheerfully accepted.

davnport

Ok, I have a new code, C1226, which points at RF wheel speed variation. Since the noise seems to be at left front, I should examine the right side wheel area for something amiss?

Cursory examination RF reveals nothing obvious. Reseated the cable but same results. Did not remove caliper to expose further. One other discovery; When the display icons 'ABS' and 'Traction control' are lighted, left side brake doesn't engage while backing. This would support ABS problems. Is there no 'turn off the abs' switch?

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Maybe a bad bearing. That will usually cause a wheel speed sensor to eventually fail. Try the "S" turn technique and see if the sound comes and goes.

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