Speed Sensor

The beat goes on

I have done a lot of reading to try solve my TCS-OFF and ABS light on problem.
The real reason to fix this problem is that this is the fundamental reason why this vehicle drives so well and handles the bad weather.

I took it to the dealer (this must be one of the worst in the nation) to have a diagnosis done. After a three day diagnosis I was told that the 'ABS Computer' will need replacing for $1400.
No problem says I, I have two Tribecas, I will swap these 'computers' when I find out where it is and confirm this diagnostic before spending the money. Lights stayed off all the way home and I hoped that by scratching around the dealer had inadvertently fixed it but it started again the next day. Probably only reset the fault codes.

And so the study started.
The Result is that there is no such thing called an 'ABS Computer' the Vehicle Dynamic Control (VDC) Control Module & Hydraulic Control Unit (VDCCM&H/U) module contains all the computing and hydraulic controls. A mouthful.
This unit is easily accessible, R/H side of the engine compartment, but looks like a whole day job that will disable both vehicles so I have nothing to report there yet.

The vehicle with the fault lights has an odd tire with more tread, and both vehicles needed tire rotation, so on an off chance I swapped and rotated wheels between them. This did not solve the light problem nor did it solve the hum which is getting quite noticeable >50MPH.

So it was back to the manual and forums.
There is a procedure to determine the faulty component in the system by the Diagnostic Trouble Code (DTC) reported by the Subaru Select Monitor. Could be I should trust the dealer and hope they saw the code for the VDCCM&H/U.
My studies show that the DTC provided on the ODO/TRIP meter using this method have no bearing on the fault code I need. This is known as the Combination Meter System and provides codes for ECU and TCM.
It does however display communication errors between devices when they occur.

The FreeSSM software and cable only gets you access to the Engine Control Module (ECU) and Transmission Control Module (TCU) so that is useless for my diagnostic.

I am a stubborn one and want to find this myself. I get to learn that way.

Next test is to hook an oscilloscope to each wheel sensor and see what the output looks like. Supposed to be a square wave between 0.7V and 1.4V across a 100 Ohm resistor according to the manual.
Hope to find a faulty wheel sensor.

After that, it is getting the right day for swapping the VDCCM&H/U between the two Tribecas.

Keep you posted.

How does a leaking hot water heater help solve my TCS-OFF and ABS light on problem?

Its a long story.

Just before Christmas I was at the store and a guy mentioned to me in the parking lot that there were no taillights working on the Tribeca. Only the reverse light were working.
Went home and did some troubleshooting, starting with the lamp bulbs, I discovered one element (tail light) of one of the bulbs was broken. Swapped the break light relay with the one next to it and all the tail lights started to work. Swapped the relay back and they continued to work. Conclusion: faulty relay socket contact.
Instead of replacing the broken light bulb I ordered a pair of LED bulbs on Ebay and installed them. (All part of the modernization effort)

Well the wife then noticed the TCS-OFF and ABS light illumination problem. She asked if the tail light trouble shooting I had done had anything to do with the problem. Never could that be the cause, what does she know.

Fast forward: After hours of research, swapping tires, checking wheel speed sensors, $200 to the dealer for diagnostics and still no closer to solving the problem.

Then the hot water heater started leaking and needed replacement. Hooked the trailer and went off to the hardware store. Drove there, forgot the straps, drove home and back to the store, collected the hot water heater and drove home. All this driving and the TCS-OFF and ABS light did not illuminate.
I had got used to when the failure lights would typically illuminate: Turn on the ignition and start driving then after the first stop it would normally trigger the failure.

Thinking: The extra load of the trailer lights is being sensed by the electronics to indicate that the brake light bulb current load is enough to show that the bulbs are working. This load was below tolerance because of the LED light bulbs in the circuit.
Also it seemed that the longer first brake pedal push the sooner the TCS-OFF and ABS light would illuminate. Indicating that it is a function of current and time that is being sensed by the computer.

Verified my theory by unhooking the trailer and the failure re-occurred.
Confirmed it further by replacing the LED light bulbs with the correct 7442 bulbs ($5), and the TCS-OFF and ABS light on error problem has been resolved.

Lesson: The vehicle electronics is smarter than it first appears, it can detect a pair of broken brake light bulbs. There is no warning light specifically for that so it illuminates the TCS-OFF and ABS indicators.
Thinking about it, the vehicle stability did not seem impacted by the illumination of the warning lights.

Also, there is no way my local Subaru technician would have solved this problem, even with a Select Monitor. They were about to change the 'ABS computer' for $1400.

Remember: Don't use LED bulbs unless the vehicle is designed for it!