2005 Impala "Service Traction system"

My vehicle is a 2005 Impala LS with 3800 v6, 81000 miles. When it was parked on Saturday all was well. When I started it on Sunday morning, the "TRAC OFF" light and "ABS" light remained lit, and the chime bonged like crazy. The message display showed "Service Traction System". The CEL light goes off shortly after engine start like it normally would. While driving on the highway, all seems normal except for the "TRAC OFF" light and "ABS" light being lit (chime stops after about 15 seconds, and message center goes blank after about 60 seconds). No anomalies noted when braking, though I haven't braked hard enough to engage the ABS. A local mechanic hooked up a code reader, but it indicated "No codes". The only work done recently was changing the snow tires for summer tires, done in my driveway 3 weeks ago. The dash was dis-assembled a year ago to repair the instrument cluster (replaced stepper motors). Last fall the local GM dealer replaced the heater core, though it turned that the condensation on the inside of my windshield was not coolant as they said it was (never going back there!). The car has not been driven by anyone but myself, and that has been on paved streets around town. Nothing hit that I know of that might have damaged anything under the car. Any ideas on what to look at? I am considering dis-assembling the dash to check the TRAC OFF switch, and removing the wheels one at a time to see if anything looks out of whack there.
If the ABS light is ON then there is a code(s) but you would need a scanner capable of doing so.

Bad front wheel bearings or the ABS speed sensor wiring that is clipped to the front lower control arms gets damaged seem to be the most common.
:) Thanks for your reply. I think I'll visit my mechanic again to see if he has a different scanner. I trust him as he has done work for me before. I am thinking, as you are, that maybe the wiring at one of the wheels is broken or corroded. Here in Utah they use a lot of salt on the winter roads. And sometimes I force my way thru the heavy crusty snow that the plow piles up. That may have damaged something. Wheel bearings seem to be OK.
I just pull the ABS module connector off and check the resistance for all four sensors, should all read the same, even detects the weak ones that are about to go soon. No single cable goes to each wheel, has connectors buried all over the place. Then check the resistance right at the wheel sensor.

Some have separate sensors with a single bolt, but not yours, damn it, part of the wheel hub.


Have to replace the entire wheel hub if the sensor is bad. Vast majority of ABS coded deal with the sensors, others are with the ABS main and pump relays, and the ABS pump itself. If the ABS light comes on and stays on, typically and open or a short in any of the sensors or the relays have dirty contacts, the so called static mode. With a low output signal, and resistance even close, ABS light will go off, but will come on after you hit about 5-8 mph.

Looks like yours is a two pin, just a coil of wire in there. Did destroy a good hub just to see that coil, idiots couldn't even put t thin coat of silastic on it, immersed in epoxy where constant thermo cycling broke off the top layers of that coil. What a cheap piece of crap.

Let me know what your ,mechanic gives for an estimate with ABS problems. One of my kids took his car in for an estimate, wanted more than what his car was worth. Fortunately, just got by with a poor connector, cut it off, and soldered it.
I agree.....if the ABS light is on, then a code is set.....most scanners/code readers only can read "P" codes......ABS codes are "C" codes......

Don't pull any dash apart.....as stated, more often then not, it's the hub assembly or the wiring harness to it.....if there is water intrusion, BOTH have to be replaced......the code will point you in the direction of the right circuit....
Would need someone with an IQ of greater than two to explain this to me. When any idiot or even a kid can buy and install any brake part from any store and improperly install with with no restrains whatsoever. Ha, I was buying brake parts when I was ten years old.

If you read any owners manual, states don't worry if your ABS will still have normal service brakes. But they don't seem to mention if your ABS module has a shorted transistor or corroded solenoid valve, you won't have any brakes to that particular wheel at all. In theory at least, ABS is a secondary system.

But then if you read all this literature on affordable scanners, they state, due to liability reasons, we do not offer the reading of ABS codes. So need to raise at least 4,000 bucks to buy one.

Now its law to have ABS, wish my congressman was with me this morning that passed this law. Had an ice rain last night, if I hit the brakes hard enough, all four wheels would lock up. No differential signal from the two opposite wheels, ABS didn't even come on. Had to leave before the salt truck drivers woke up, but again, sure wish I had studded snow tires on my car that were outlawed a long time ago.

All that scanner tells you is which wheel is bad, but still a long ride from that ABS module to that wheel sensor. Even found a problem in the ABS module itself due to a poorly soldered I/O connector. Yeah, was a label on it, do not open, no user serviceable parts on the inside. But feel the major reason of that label is they didn't want you to see the cheap crap on the inside they were charging a fortune for.

If your ABS is not working, even if some idiot hits you, his insurance company wouldn't be liable because your vehicle has a fault in it. Tell me I am not being truthful in this response.
" Had an ice rain last night, if I hit the brakes hard enough, all four wheels would lock up. "

Typically, ABS won't work at speeds below, say, 10mph. So if you were crazy enough to go that slow on ice, you might notice an "ABS problem".
NickD, you think ABS is suppose to make you stop on ice? If you had base brakes, and you hit them hard, your wheels would lock up and you could spin.....so what do they tell you to do when on ice with base brakes?...pump the pedal like hell.....you could never pump the pedal as fast as an ABS module.....

What ABS does is give you "control" during a slide......which may allow you to steer away from trouble rather than slide/spin into it....
Not sure I want to get into this discussion, one thing for sure to activate the ABS is to get a flat tire on one side. ABS is only activated besides applying the brakes, is to have unequal pulse trains from opposite wheel sides. We can go on about the conditions that cause this.

So how do you get unequal pulses when slamming on the brakes with all four wheels on solid ice? Not a good idea to slam on your brakes either under these conditions. But many idiots do, sliding right through a four way stop sign.

Major vehicles I find in the ditch are 4WD pickup's with an empty bed. Front end is way heavy, get some traction there, but the light back end just spins around. ABS or not.


Full Member
Had a similar issue with a 2005 Pontiac, code pointed to left front wheel sensor. What wiring I could see looked good, unplugged connector and checked sensor with VOM. Buttoned everything up and no problem since. Go figure.
Putting your pickup into 4wd on snowy roads can give you a false sense of road conditions. It fixes your wheelspin problem during takeoff, you smile and think "Yeah, these roads aren't slippery now, so I can drive like I always do!" And so you hit the brakes about 50 ft before the stop sign like you did all summer, and end up sliding through the intersection (if you are lucky)!
Thanks to all for their help. Found someone to read the ABS codes. Shows 2 codes:c1223 and c1234. One indicates open or shorted sensor at the LR wheel, the other indicates no signal from LR wheel. Following tests were done at the LR wheel using a Fluke 73 DVOM. Checked the harness for continuity: OK. Checked DC voltage at the wheel with key on: 5.03VDC. Checked resistance across the pins of the sensor and got 120K ohms (checked several times to make sure). I've heard thru the grapevine that the resistance should be much lower, somewhere between 1000 and 1300 ohms. Is that correct? If so, it looks like I may need a new hub. Problem here is I absolutely will not take it the dealer. They did an incorrect diagnosis last year that cost me a lot of money for parts and labor that were not needed. Not sure who else to trust to fix it.
Sounds like my kids cars when parked in Madison or Milwaukee in college and had to park their cars on the street to get mostly the left side blasted with those salt trucks. Could pull the right side brakes off with ease, left side was positively miserable.

Recall around 1200 ohms to be about right, and gather you tested right at the sensor terminals on the hub. Did you clean off those pins with 600 grit wet/dry sandpaper first. If oxidized, no amount of probe pressure would break through that stuff, those pins have got to be bright. Then the pins on the connector.

Who do I trust to change hubs? Me of course, caliper has to be removed, use a larger C-clamp just to push the pads in a bit so they clear the rotor, use a piece of wire to hang it as not to kink that hydraulic hose.

This one is held by four bolts, have to align those holes in the flange to remove those. In theory at least, old hub should just slide out. This one doesn't look as bad as some, that flange that fits into the yoke doesn't look that deep, Using an air hammer with a chisel on the outside flat side on the inside. Don't care about that old hub, but want to protect the hub. May not be a bad job. See new hubs are as cheap as 50 bucks each.

Can also check the resistance of the sensors on the other side, all four should read the same.
Many thanks, Nick. Pins were nice and bright. No sign of water intrusion. I don't have any air tools, but I'll have a go at it anyway. I'll get a hub ordered (from NAPA perhaps). Meanwhile I'll check the other sensors. Wish me luck!