ABS Light With No Codes

[MassHoe04]

then they must be historical codes, must be things that a previous owner fixed because a bad knock sensor would def have a check engine light on
when you swap the sensor, if the code follows then it is a bad sensor if it stays on left then it'a bad hub
I am guessing it's not really a broken wire then because it wouldn't read at all and you would have trouble coming to a complete stop because the abs would be kicking in
swapping the abs sensor is simple, it's 1 bolt and a couple clips that hold the wire along the control arm and then it unclips from the harness. left & right are identical.

On Sunday, there were 8 of those codes in the "Chevrolet OEM Enhanced - ECM" section of my scanner. I cleared them. Today, there were 11. The same 8, plus another 3. Two were related to knock sensor circuit low voltage.
They weren't in there Sunday, but now they are. I agree, there should be a CEL, if sensors were bad. Engine purrs like a kitten and no CELS or DTM codes. Feels like the system is almost making these things up. Or maybe the scanner can't really clear codes stored in that part of the computer... ?

 

[TJ Baker]

Just tossing this out here for what it's worth. The trouble with scanners is they don't always tell you the true status byte value but their intepretation. I read my codes hands-on, issuing the requests with a serial terminal so I see the actual response from the module, not some softwares translation.

First image is from SAE J 2190 describing the 8 levels of code status.



Second image is an annotated screenshot from my reading of codes from a PCM using a mode $19 request and asking for all codes with bit 5 set. May look like confusing gibberish but it isn't really all that hard to do and only requires a $15 OBD2 adapter.



Last image here is some of the basics of decoding the messages...

 

[MassHoe04]

Just tossing this out here for what it's worth. The trouble with scanners is they don't always tell you the true status byte value but their intepretation. I read my codes hands-on, issuing the requests with a serial terminal so I see the actual response from the module, not some softwares translation.

First image is from SAE J 2190 describing the 8 levels of code status.

View attachment 356231

Second image is an annotated screenshot from my reading of codes from a PCM using a mode $19 request and asking for all codes with bit 5 set. May look like confusing gibberish but it isn't really all that hard to do and only requires a $15 OBD2 adapter.

View attachment 356232

Last image here is some of the basics of decoding the messages...

View attachment 356233

Thanks! I am fairly tech. savvy, but my head was spinning a bit after seeing that. I do get your point that the scanners do a bit of interpretation and translation that may or may not be the full or true story... Thanks for the information.

 

[Walchit]

Switch those abs sensors around. I was getting an ECBM motor relay circuit code, because the new sensor I put in was shorter that the original, I had to remove a shim, and now everything seems fine.

 

[MassHoe04]

Switch those abs sensors around. I was getting an ECBM motor relay circuit code, because the new sensor I put in was shorter that the original, I had to remove a shim, and now everything seems fine.

I decided I won't bother swapping sensors. I have a new Echlin sensor waiting at NAPA for me.

 

[Walchit]

Look at it next to your old sensor, and use the shims to make sure it's the same distance from the tone ring. Then you shouldn't have to take the caliper off twice like I did, lol

 

[MassHoe04]

SOLVED!

I finally got to front rotors, pads and looking into the ABS sensor issue that was driving me bonkers on the highway... The issue I had was ABS check ran OK on start-up, no ABS lights/chimes driving anywhere around town. Only on the highway, after a couple of miles, the light/chime would come and go constantly. On my weekend commute of 30 miles each way, the chimes were driving me insane! Then they would go off and stay off, once I got off the highway and drove less than 50/55 MPH.

Potential suspect causes:
Bad wires/connections.
Bad sensor.
Bad hub.

Instead of cleaning and replacing the old sensor in the same hub or swapping positions with the problematic left sensor over to the right side to see if the issue follows or replacing the entire hub with a new one including a new sensor, I decided to try a new sensor first. Fewer steps and less chance of having to re-do hub and brake removals.

I bought NAPA brand ABS sensor (Echlin in this case) for $38. NAPA Part # UP 531158.
I got it on sale and had $5 in rewards points to use. Final total cost for the order was $28.90.

Hub was solid. It rotated easily and smoothly. It made no unusual groans or grinding noises. That was promising.

I pulled the old sensor out and inspected. There was a single shim under it, but the sensor looked like the tip was grinding into the reluctor ring in the hub. Kind of looked like the tip of the sensor was ground off and slightly curved. Maybe the last time the ABS light/chime came on, someone ordered an Amazon special or generic part that was just a hair too long. Not sure...



I sprayed down the reluctor wheel with BrakeKleen and blew it out with compressed air. That cleaned up the ring good. There was a very slight groove in the ring, probably from a sensor that was too long grinding into it... But, it didn't look too serious. I test fit the new sensor. It seemed like it made slight contact, so I re-used the single shim that was under the old sensor. Felt like it cleared perfectly. I put it in and completed the front brakes.

ABS test on start-up was OK. Things were off to a good start. No light/chime around town. Also a good sign. Real test was my usual weekend commute on the highway Saturday.

As of Sunday, I have driven 3 runs on the highway of 25 miles each. Highway aversion therapy is finally over!!! My sanity has been restored! No ABS lights or brain piercing chimes!!! I actually love driving my "new" Tahoe on the highway now. It just cruises along nice and quiet. These are fantastic vehicles and I am glad I got into one!

Thanks for all your support/advice! I managed to get off the hook pretty cheap and easy on this one. I am happy my Zurich scanner from Harbor Freight was able to narrow down the issue to the left front sensor. That saved me a lot of time trying to find the source of my problem and save me a lot of money by me not just replacing all the sensors to see what worked.

Thanks!

P.S.: Raybestos pads and rotors from our forum sponsor, RockAuto, for less than $100 shipped! Could not be beat. I normally go premium coated, but had to do a budget job this time. Similar basic pads and rotors were averaging about $200 locally.

 

[Walchit]

I'm happy for ya! I got mine for the wife/family hauler, so I feel like ABS is a necessity. I would have probably re-soldered my ABS module if I didn't buy the scanner, so I feel like it's probably paid itself off already.

 

[corvette744]

Good info guys.