Uncommanded ABS or Advancetrac braking

[ICoull]

2003 Eddie Bauer with AdvanceTrac. Just replaced front differential, so had front hubs removed/replaced. No DTC’s and using Forscan to track all four wheel speed sensors, they all agree. Issue is repeated cycling of brake(s) at speeds above about 15 mph. Turning AdvanceTrac off makes no difference. Traction assist valves (right and left) show no activity when Uncommanded brake action occurs. Wondering if a wiring short is activating system?

 

[Fix4Dirt]

2003 Eddie Bauer with AdvanceTrac. Just replaced front differential, so had front hubs removed/replaced. No DTC’s and using Forscan to track all four wheel speed sensors, they all agree. Issue is repeated cycling of brake(s) at speeds above about 15 mph. Turning AdvanceTrac off makes no difference. Traction assist valves (right and left) show no activity when Uncommanded brake action occurs. Wondering if a wiring short is activating system?

thats odd that wouod point to a short or some other gremlin. nit sure if this applies to the later gens but on 2g theres 2 big ole harnesses in the engine bay that can cause lots of weird issues here and there, wonder if thats worth a shot?

 

[ICoull]

thats odd that wouod point to a short or some other gremlin. nit sure if this applies to the later gens but on 2g theres 2 big ole harnesses in the engine bay that can cause lots of weird issues here and there, wonder if thats worth a shot?

I’m wondering the same thing. I’m going to prop all four wheels off the ground and try to induce the problem when it’s running by manipulating the big wire bundle going to the abs module.

 

[Tekreck]

My son’s F-150 had a pin on ABS connector corrode (sealing gasket around connector had been pinched) and when connector was removed, the pin came out with it. I ordered a new pigtail and got used ABS and spliced pigtails 38 wires into harness. My point - I’m on a first name basis with the connector. Remove connector and disassemble the cover from the core and visually examine. Not hard. Cap with lever slides down cable and there is a press-inward latch on each end of connector to separate.

If you unbolted / removed sensor from wheel bearing / hub and reattached, debris inside hub could cause random triggers. Be nice to isolate front left or front right or rear.

 

[ICoull]

I’m wondering the same thing. I’m going to prop all four wheels off the ground and try to induce the problem when it’s running by manipulating the big wire bundle going to the abs module.

Not useful approach as open diffs allow one front and one back wheel to spin, other to stop. Not analogous to driving with all four wheels on the ground. Even so there was a regular brake pulse being sent through the system although it was not clear which subsystem ABS or Advancetrac was doing that. Removed and looked at engine bay connector (sprayed with electrical contact cleaner), then reassembled. No change. Seems more likely a shorted component than a failing connector as one or more solenoids is activating one or more of the calipers at the wheels. I’m going to swap in an ABS module from my 2005 parts Explorer and see what that does. Ugh.

 

[ICoull]

Not useful approach as open diffs allow one front and one back wheel to spin, other to stop. Not analogous to driving with all four wheels on the ground. Even so there was a regular brake pulse being sent through the system although it was not clear which subsystem ABS or Advancetrac was doing that. Removed and looked at engine bay connector (sprayed with electrical contact cleaner), then reassembled. No change. Seems more likely a shorted component than a failing connector as one or more solenoids is activating one or more of the calipers at the wheels. I’m going to swap in an ABS module from my 2005 parts Explorer and see what that does. Ugh.

Ok. 2002 and 2003 ABS with Traction Controls do not interchange with older or newer ABS modules… But I know now that there are 4 separate 12 v inputs to the ABS module. Removing the two sourced from the underhood fuse box disabled the actual Uncommanded brake applications ( sharp shocky applications) and allowed some test driving at more than 10 or so mph. I’m now convinced that a low power ( internal electrical short) inside the electronic control was creating a continuous buzzing application of the ABS function at all four wheels. Felt like a bad bearing but was a ‘buzzing application of brakes’. Have ordered 2003 specific ABS unit and expect problems to be solved. Additional symptom was all four brake rotors were heating up.
Aug 24, 2022 update:
Update… used ABS electronic module ( did not change out the hydraulic valve block this time to avoid re- bleeding brake system) installed, re programmed using Forscan , and ABS Forscan mediated bleed procedure executed. No DTC’s after swap and reconfiguration. Test drive at more than 10 mph SAME Uncommanded brake activity every few seconds. Back at square one it seems!
Remaining suspects involve Advancetrac sensors on steering, brake booster, and the main lateral/ acceleration g meter in the center of the body. Advancetrac Guru’s feel free to comment.