Posted: Tue Jun 14, 2011 11:27 pm Post subject: ABS problems, 2002 Impala
My son's 2002 Impala is giving him some ABS problems. The system occasionally turns on the ABS light, and it's happening more frequently. He says the problem seems to coincide with making turns and running thru our alley way. The alleys are dished so they load the wheel bearings differently than a typical flat or crowned roadway. An intermittent, low humming noise also occurs.
I've heard the noise in the past and it's hard to identify. It sorta reminds me of wheel bearing noise, but it seems a little louder. And it's intermittent, so I'm doubtful it's wheel bearings. Plus, we just put new Timkens (from Rockauto) on the front a couple months ago - surely they haven't died that quickly. When we put them on, the noises and ABS problems seemed to go away.
But now they're back. We're getting these ABS codes:
DTC C1221 LF Wheel Speed Sensor Input Signal is 0
DTC C1225 LF Excessive Wheel Speed Variation
DTC C1226 RF Excessive Wheel Speed Variation
DTC C1248 Dynamic rear proportion (DRP) )disabled
If the wheel hubs weren't brand new, I'd think that was the problem.
I checked the wiring harness to the RF wheel. This bulletin. found on this forum, indicates that's a common problem, but I've carefully examined that wiring and don't see any signs of failure. (But now I need to get some new wire loom and put everything back together )
So, what could the noise be? Does the ABS system make low, humming noises? It's definitely not the sound of the ABS system engaging. That noise is much louder. Could one of these new hubs have somehow failed so soon? Does the ABS Control Module make noises other than when pulsating the brakes? How can I diagnose this? Thanks.
If new hubs were put on, then they should not make noise. Looks like on the left front the sensor inside the hub could be fragged. Were the hub nuts torqued to the proper torque?
Thanks for your reply.
Yes, I used a torque wrench, and new bolts. 96 foot-pounds per the Haynes book.
Could the noise be some sort of low-level assertion of the ABS system? It's definitely not the normal sound of the ABS kicking in, but I wondered if there's another, lower level that would make the sound I'm hearing.
Visually inspecting the hubs, they look fine.
I need to see if I get the sound with the ABS system disabled. That should help me eliminate some of the possibilities.
/// [Edit] I just got it buttoned back together, took it for a drive, and everything is fine. No codes - none - zip - nada. Go figure.
The other day, it was giving codes for both front wheels, the car was making noises, and the ABS light came on.
Since then, I went thru the front right sensor cable inspecting for breaks all the way back to the split near the starter. No signs of breaks, so I put it back together. Included with that were several insertions/extractions of the connecter at the hub to clean the connector contacts, thinking maybe a poor connection there could be part of the problem. Did the same on the left front connector, too.
I then cleared the codes, took it for a test drive, reading the codes repeatedly, with no sign of problems. No low, grinding-humming noises, no ABS light, no nothing.
For now, I'm relieved. But, as much as I wanna believe it's fixed, I can't help but think this isn't the last we've heard of this. I'll keep my fingers crossed it doesn't come back any time soon.
I recently purchased the Impala and there is ABS light. Could you please explain how you figured out the ABS codes? (I think I need to check them too)
Did you use soething like OBD II Scanner or somthing else?
You need a scanner that does ABS codes. Most of the cheap OBD2 things the auto parts stores sell don't do this. You can either go to a shop and have them pull the code for you or go and buy an expensive scanner.
Protip: If you don't know what you're doing, don't do it.
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