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Stilettobob 04-05-2016 03:22 PM

ABS Light on but no OBDII Codes found
So I just got this 2003 Ion 3 Sedan for my son's first car. Everything is sweet about the car with the following; The ABS light on the dash is illuminated. I've run an OBDII code diagnostic and there are no codes. The previous owner said it might be the wiring harness. Anyone out there able to provide some guidance before I start tearing things apart?:xeye:

fdryer 04-05-2016 03:45 PM

Re: ABS Light on but no OBDII Codes found
1-Generic low cost readers are basically designed to read emissions errors, 'P' type codes like P0341, P0300, P0422, etc.. Most low cost readers will not decode many other error codes with prefixes; 'B', C', 'U', and 'N'. ABS error codes are 'C' type. Google 'ABS error codes' for a general list that aren't read by most readers. You may be in luck if your local Autozone has the newer updated reader capable of reading abs error codes. Call or visit one if you have one nearby as other members just started reporting their Autozone's are now reading abs error codes.

2-The previous owner is more or less correct. ABS faults basically falls into three areas that are all external to the abs control module sitting next to the brake master cylinder and protected in the engine bay; all external wiring from abs module to each wheel, the wheel speed sensors and the reluctor (the toothed steel ring used to help generate timing signals from each wheel speed sensor).

Having a reader decode abs errors narrows down the problem immensely otherwise it can be as simple as a visual inspection of each wheel where the wiring, wheel speed sensor and reluctor are mounted. Some parts are hidden in some models while all parts are visible in other models. Damaged reluctors are usually cracked or missing altogether. Wheel speed sensors are damaged, bent in their brackets or out of range/dead (ohm resistance). Wiring from the abs module to each wheel speed sensor can be obvious when inspecting where wiring is tied/clamped.

fdryer 04-05-2016 04:37 PM

Re: ABS Light on but no OBDII Codes found
And while I was distracted, I forgot to mention the check engine light doesn't turn on for abs errors because the abs light turning on and staying on is the indication that abs errors occurred and stores the code in either the abs module or passes it on for storage in bcm memory for retrieval by better readers. Outside of emissions error codes, I think abs errors are stored in the abs module. The bcm acts as the electronic gateway for communicating with the ecm/pcm, abs, airbag, tcm, OnStar and other modules communicating thru canbus wiring. Original (OBD I) comms are serial but became too slow as more modules were added, forcing engineers to use canbus comms for higher comm speed. This created problems with readers originally wired for serial comms. The OBD II port connection for readers are serial but the extra pins on some OBD II ports in our cars are for canbus communications requiring readers with the ability to connect to canbus pinouts to retrieve the error codes not read from readers using the serial pinouts. More electronics, more comm protocols, more expensive readers/scan tools..........

Stilettobob 04-06-2016 04:46 PM

Re: ABS Light on but no OBDII Codes found
Thanks for the response. Just came back from my local garage to check out any OBDII codes..... There were none. No DTC. Nada. Nothing. On the way back from the garage I simulated a panic stop. The ABS did not kick in. No pulsing what so ever. I returned home, completely disconnected the battery, reconnected the battery. Still the ABS dash indicator is illuminated. I tried to turn on the traction control by pushing the TC button. It did not light up either. Hummmm. What to do. What to do.

All help is very much appreciated.


fdryer 04-06-2016 08:33 PM

Re: ABS Light on but no OBDII Codes found
Traction control [I]is[/I] ABS but used in the opposite sense - ABS prevents wheels from locking up by releasing and braking at high speed just short of locking any brake as long as high pedal pressure is applied and a wheel or wheels are not in contact with a surface to slow it down. Traction control does the opposite by stopping a wheel from spinning up compared to the other drive wheel by using the same abs technology without a driver applying brakes. The abs unit applies braking to the wheel that spins faster than the wheel having traction. the reason the abs light is ON without a check engine light is as explained before; abs is completely self contained and indicates its status with one light, the ABS light.

1-OFF = ignition is OFF or ignition is ON, engine running and car is moving above 5 mph/8 km/h.

2-ABS flashing = abs actively cycling at high speed one or more wheel brake to prevent brake lockup to allow as much traction as possible while slowing the car down.

3-ON = ABS detected a failure during power up self tests(@ignition ON time) or while driving and completely disables itself from interfering with braking. Thiis means ABS is no longer available but does not prevent brakes from operating as they always do.

As you found out, without abs the brakes are still working and can lock up any wheel(s) on slippery uneven surfaces.

Try Autozone's reader or consider a walk around careful inspection of; wiring to each wheel speed sensor, sensors and reluctors. At home diagnosing with error codes read by A-z or visual examination of ABS components are the least costly methods. Paying GM or brake shop capable of decoding and repairing abs will cost more unless asked to perform diagnostics and provide a report for you to make any repairs.

2006 ion2 04-07-2016 02:01 AM

Re: ABS Light on but no OBDII Codes found
I had an abs light on my van touchy after we bought it. The abs malfunctioning (light on) disables traction control and possibly cruise control, also. That button disables tcs, not enable.

Do you have a bad wheel bearing? I've had this happen on gm vehicles and disable abs because the damage extended into the elucidate wheel. On my van, we were able to read the codes with the reader at advance auto and it pointed out what wheel was the problem. Then you just have to determine if the wiring is bad, or in my case the wheel bearing was bad.

The abs choose will tell you what circuit is bad, if ions are 3 channel you would only get a channel 3 error for the whole back. In either case, you remove the suspected wheel(s) and disconnect the connector. Measure the sensor for an open. If it's not open, spin the hub and measure for voltage. It's a slight voltage, but it should be there and constant with constant wheel speed, not jumping around. If this isn't the problem, then you need to look into the wiring.

Stilettobob 05-05-2016 12:21 PM

Re: ABS Light on but no OBDII Codes found
sorry for taking so long to respond. Just got the car back from the RI emissions test and had them put it on the super duper OBDII code reader. Came up with a C0045 & C0046 indicating a bad left rear speed sensor/wiring harness issue. I'll follow the above advice and hook a VOM across the two sensor pins and expect to see voltage. I'm also thinking of breaking the rear brake wiring harness under the back seat and check from there which might rule out the exposed (and suspect) rear wiring harness to the rear left wheel sensor. What are your thoughts?

2006 ion2 05-05-2016 02:13 PM

Re: ABS Light on but no OBDII Codes found
You hit it on the head. It's either the sensor, or the wiring. If it's the wiring, it would be the section of harness you mentioned.

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