I'm starting this thread to document and track progress on this issue I'm having with my 2013 GX460. The issue began when my wife reported that her dash was lit up with blinking lights: ABS, Traction control, 4Lo and some others. She thought it was related to the heat, as it would come and go.....

This picture shows what it looks like: ABS, Brake and Traction lights are illuminated. 4Lo, CDL and MTS lights are blinking. No Check Engine Light.

 

I've had the secondary air injection pump warranty repair, and this is not that issue. There is no CEL, just the other dash indicators as shown. Fortunately I have a copy of Techstream TIS, and was able to plug it into the OBD2 port and see if anything showed up there. In the Chassis->ABS/TRAC/VSC section, Techstream showed DTC C1408 - Open or short in left rear speed sensor circuit.

Most (all?) cars with ABS have speed sensors at each wheel that are used to detect speed at the wheel, and pass that signal to the computer for logic determination for the ABS/VSC/TRAC systems. Usually it's an easy fix, albeit somewhat expensive for a little plastic part. While the code indicates a wiring condition, I assumed it was a faulty sensor and that was step 1.

Toyota/Lexus part number 89543-60050 for the left rear speed sensor: retails for just under $200.

Given that my diagnosis was a failed OEM part at 75k, at that price point I decided for the Chinese knock off that I found on Amazon for $25 for a pair.

This is what the part looks like:

 

It's an easy R&R for one of these sensors. It mounts to the wheel hub on the opposite side of the brake caliper (toward the front of the vehicle on the driver side). It's the only thing with a wire coming out of it on the wheel. A single M6 (10mm) nut holds it in place. Remove the nut, and wiggle the plastic piece up and out of the wheel. The wire connector is weatherproof and a bit snug, so it takes a bit of wiggling and a small screwdriver to separate the two. Once you get this done, then pop the new sensor into the wire connector, push it into the hole on the wheel, and secure the nut back in place.

 

After I installed the new sensor, I used Techstream to clear the DTC C1408. There was a similar DTC on the KDSS page which indicated a general malfunction of a speed sensor. I cleared this as well.

My wife took the GX to Denver the next day, and the dash lit up again.

 

There's certainly a possibility that the sensor I received was bad, but I'm not convinced at this point. The other potential issue is that the wiring itself has an issue: corrosion, moisture, damage to the wire, or something similar. When I separated the connector to install the new sensor, the inside of the connector looked brand new - no evidence of rust, corrosion or any dirt. I did a cursory clean up and added some dielectric grease just in case, but I don't think that connection is the issue.

The wiring for the rear ABS is a single harness that has a connector above the top of the rear axle, and then runs out to both wheels for the sensor connectors. Toyota PN 89516-60300 - Skid Control Sensor Wire, and retails for around $100.

But doing a bit of Googling on the issue to see if other GX's, Tacomas, 4Runners or similar have seen this issue, I found limited data. A lot of intermittent codes and resets, but nothing systemic from what I saw. But I did find this interesting Russian site for Corollas.

https://corolla-club.ru/doc1/b6ff07e...0f1aba30b.html

Translating the page, it's a great resource for troubleshooting these trouble codes. The most interesting thing I found was this section:


C1407 Open or short in right rear speed sensor circuit

Any of the following conditions are logged: C1408 Open or short in left rear speed sensor circuit

Any of the following conditions are logged: Note the 3 Defective Site possibilities: The sensor, the circuit (wires) or the Skid Control ECU. That latter part, the skid control ECU, is central to the system that I've impacted by replacing the Driver Support Computer (to add MTS I added part number859A1-60020). Makes me wonder if that new computer has somehow affected the Skid Control system in such a way that is causing the DTC. I haven't seen anyone else report this issue, so it may not be the cause, or it may be a problem with my part specifically.

I think at this point, before I spend the money on new wires, I'm going to reinstall the original computer and see if the trouble codes go away. That should tell me if the new part is the source of my issue.

 

Interesting.. keep us posted.

Hopefully it isn't a critter related issue on the wiring.

 

I've gotten some bad goods from China lately so I wouldn't rule out a bad sensor too. I'm actually getting eBay to force a Hong Kong seller to pay for shipping back at like $40 on a $100 item.

 

How long ago did you install the MTS computer?

I installed my computer and the crawl control last month. I then took the truck our for a week long trip in the Northern Sierra's using both crawl and MTS quite often (the ABS solenoids definitely got a workout) and haven't had an issue. I've put about 2,500 miles on my truck since the install.

 

I've used mine quite a bit now as well. I've got about 4500 miles on mine since February install.

 

It was back in April. CC just recently, but the DTC's were happening before I installed the CC switch, but after I installed and activated MTS.

Good news is that I installed the original computer, and even after letting the battery rest for 20+ minutes, I got the same error and dash lights. With the old computer, the MTS indicator wasn't illuminated along with the other dash lights, so I know the system was reading the computer correctly. So I can all but rule out the Driver Support Computer change as the cause.

I'm back to the possibility that the wiring has a short, or the sensor(s) are bad. Visual inspection of the wire shows nothing - it looks clean and in tact from the wheel all the way up to the next connection. Next steps TBD.

 

Did you check the connector above the rear axle? Maybe check the connectors at the skid control ECU?

 

I did a basic check - it looks cleaner than the connectors at the wheels. The trouble code is specifically pointing to the LR circuit so I'm focused on that one. At this point, running full diagnostics using the data list in TS and checking resistance numbers is the next step.

 

If you do find it is defective aftermarket sensor and want to go OEM.

Motor Heads Japan has it for $107.78 plus probably less than $10 shipping. This is the place that sells the 020 MTS module.

It isn't searchable on their site... I had to email them.

 

Thanks. That's a good price on the sensor.

 

If one is looking for small interior plastic trim pieces that are also used on other JDM Toyota models or the Prado you can usually get them pretty cheap from that place. Shipping is cheap too on small parts.