Please please help - ABS / TC Light on. Ive tried everything.

[Julian28]

2012 VE SSV
My ABS and traction control light started coming on every now and then, now it's all the time as soon as the key is turned on.


Time line of things I've tried
- Tested battery. Fine

- Replaced rear wheel ABS sensors. Did nothing.

-Took to the mechanic and they tried different sensors,
tested the loom,
replaced the front right sensor as their scanner said front right and back left sensors bad.

-I've taken the back left hub off for the mechanic the replace the wheel bearing incase the magnet had gone bad in the bearing. Mechanic says the magnet is fine no need to replace.

Next thing would be to replace the ABS computer unit up the front?
Not sure, I need help.
Any ideas
Thanks

 

[Fu Manchu]

Is there continuity between the sub harness sensor plug and the other end of of the harness? What if you go changing modules but nothing changes because no one checked the wiring integrity?

When he battery was tested, how was that done?

 

[Skylarking]

One often needs a oscilloscope and/or an old school analog multimeter to work on modern cars as digital multimeters can do funny things with pulsed voltages that are often used for signalling.

So the process should go as follows;

1. load test the battery
2. check the DTC's
3. as a starting point, check the suggested workflow for fixing the listed DTC's as specified in the workshop manual
4. then check the features description and the feature's circuit diagram to understand the component interplay, wiring and any commonalities, before assuming anything.
5. assess whether the vehicles system is reporting something logical*

specific to wheel speed sensors;

6. find out where the wires for each wheel sensor goes, i.e. which module they go to, usually the abs module.
7. connect an oscilloscope (preferred) or old school analogue multimeter to one wheel sensor wire pair at the module.
8. spin that wheel and check the waveform is correct or you are getting a voltage (the voltage should increase the faster you spin the wheel)
9. repeat for all other wheels
10. check the connector at the module

Oh, it's also worth checking for any related technical service bulletins (TSB's) for related issues (if only such wasn't behind a paywall and more easily accessible to home mechanics, it would make our lives easier).

* Why, because two sensors dying at the same time is a rather unlikely possibility, so some commonality must be at play like faulty connector, faulty earthing, corupt data on canbus, etc. Problem is that internal module functionality/wiring isn't normally exposed so one may not know that a simply and repairable failure (sometimes in another module) can occur so mindless module replacement is often done by less skilled mechanics (even before isolated to a module = parts cannon approach).

At the end of the day diagnosing is complex when the feature is complex and unfortunately there's no getting around that. End result is many mechanics and dealers dont like complex issues and prefer simple and profitable oil changes and basic service.

Good luck.

 

[hademall]

One often needs a oscilloscope and/or an old school analog multimeter to work on modern cars as digital multimeters can do funny things with pulsed voltages that are often used for signalling.

So the process should go as follows;

1. load test the battery
2. check the DTC's
3. as a starting point, check the suggested workflow for fixing the listed DTC's as specified in the workshop manual
4. then check the features description and the feature's circuit diagram to understand the component interplay, wiring and any commonalities, before assuming anything.
5. assess whether the vehicles system is reporting something logical*

specific to wheel speed sensors;

6. find out where the wires for each wheel sensor goes, i.e. which module they go to, usually the abs module.
7. connect an oscilloscope or old school analogue multimeter to one wheel sensor wire pair at the module.
8. spin that wheel and check the waveform is correct or you are getting a voltage (the voltage should increase the faster you spin the wheel)
9. repeat for all other wheels
10. check the connector at the module

Oh, it's also worth checking for any related technical service bulletins (TSB's) for related issues (if only such wasn't behind a paywall and more easily accessible to home mechanics, it would make our lives easier).

* Why, because two sensors dying at the same time is a rather unlikely possibility, so some commonality must be at play like faulty connector, faulty earthing, corupt data on canbus, etc. Problem is that internal module functionality/wiring isn't normally exposed so one may not know that a simply and repairable failure (sometimes in another module) can occur so mindless module replacement is often done by less skilled mechanics (even before isolated to a module = parts cannon approach).

At the end of the day diagnosing is complex when the feature is complex and unfortunately there's no getting around that. End result is many mechanics and dealers dont like complex issues and prefer simple and profitable oil changes and basic service.

Good luck.

So complicated

 

[Skylarking]

So complicated

Modern cars..

Just wait till they put AI in our cars and you end up stuck on the side of the road arguing with HAL9000 because he won’t drive you to where you want to go