Lexus dealership cannot figure out what's wrong!!!
 

So my car has a c1296 code come on whenever I past 60 mph,... Then it clears itself when I get back to city speeds. I also have abs pulses coming on when turning at low speeds when I'm on the brake. Dealership spent 3 hrs and couldn't figure out what's wrong. They checked the signals from all abs sensors, used tech stream etc and still don't know what the problem is. Now they think it's something "electrical".

I'm at a loss what to do next... Any suggestions or experience similar to mine is much much appreciated! Could it be a harness issue? Hopefufly it's not the 4wd or skid Ecu!!

If a malfunction in the speed sensor signal circuit occurs, the 4WD control ECU will output this DTC. When slip is detected based on signals sent from the 4 vehicle speed sensors, the 4WD control ECU controls torque distribution between front and rear wheels according to the amount of slip.


DTC Detecting Condition

C1296/96

1. When the following continues for 30 seconds or more:
◦ At a vehicle speed of 6 mph (10 km/h) or more, an open or short in the speed sensor signal circuit occurs.

2. When the following continues for 0.5 seconds or more:
◦ An open or short in the speed sensor signal circuit occurs.

3. When the following continues for 5 seconds or more:
◦ At a vehicle speed of 12 mph (20 km/h) or more, noise occurs in the signal sent from the speed sensor at the abnormal wheel.

4. While the vehicle is driving, momentary interruption in the speed sensor signal circuit occurs 255 times or more.

Trouble Area

• Brake control system (speed sensor circuit)
• Wire harness (Speed signal circuit)
• 4WD control ECU

They don't know what's wrong? You paid to have diagnostic work done any they have no resolution at all? Not even a "it could be.."?

Thanks Othic. They said they have no idea how long it will take. Could be another 10 hours was what the advisor said...This was what frustrated me the most and made me lose confidence in their capabilities. Hence I didn't authorize them to do more diagnostics. They only said it could be something electronic....sigh...
From the work order, they said they checked the speed readings on techstream, checked all sensor signals from each wheel...and confirmed the signals are all good.

I'm wondering if I should do a zero point calibration and or even do a test mode procedure to see if I get any other codes. Thought?

On ebay wheel abs sensors are pretty cheap. Might want to considers buying all 4 and installing them at an independent shop

I have heard of speed sensors going bad.

That's one option definitely... I've already replaced one of the rear sensors with no luck.

Just an update, I did the test mode procedure and got at 78 code which indicates a speed sensor rotor issue. Anyone know how to remove and inspect the speed sensor rotor?

I'm not sure if the GS has a tone ring (reluctor ring) on each wheels. If you have a broken tone ring it will give you this code. I had this issue on my RX, broken tone ring.

Take your old sensor thats good and put it on another wheel. Do that to all 4 corners it may work out for you.

Ok now a c1239 code triggered today. Foreign matter attached to sensor is what the code meant. However looking at the sensor tip it is pretty clean and this is a sensor I already replaced a month ago,,,

Could wiring be an issue?

The dealer should never tell you idk, they have t/a to help them and they could compare and eliminate issues. But it looks like they going to need a minimum of 5 hours of labor time. Good luck try a different dealer

I've lost confidence in the dealer on this matter... Anyway, I've checked continuity and the wires going to the Ecu are all good. I'm strongly suspecting it is a dirty magnetic encoder within the hub. Now I need ideas how to clean the encoder without removing the hub.... (Afraid of ruining a good bearing during the removal process)

if you are handy with the tools, here is a great article to help you. First step, inspect the tone ring, second determine the system type and then test the sensors:

http://www.underhoodservice.com/whee...rs-and-scopes/

another great resource:


http://www.cvel.clemson.edu/auto/sen...cle-speed.html

Take out the wheel sensor and then look into the hole while you turn the axle. if you cannot see into the hole get an inspection camera. They are pretty cheap now, or if you have a laptop you can get one of these:


just make sure that the hold for the speed sensor is large enough to insert the camera.


Your not going to hurt the bearing if you use a puller to get it off the axle.

Thatnks cschroder! I'm going to remove the hub .... Never tried this. Does anyone have a TIS instructions on removing the rear hub with torque sepcifications? Thx