2011 Lincoln MKT 3.5L ecoboost

a neighbor asked me if i could help him ou twith an ABS fault code : C1222-20 " no connection between ABS module and VSS". In as much as ABS module is difficult to reach, i decided to scope the RF vss. though the wheel was difficult to turn i was able to get an AC signal with KOEO with vehicle stationary. however as i left the signal going, i noticed some drop outs. could this be a module problem? i drove it around the block and when i step on the brakes, it makes that grinding sound; but as soon as the anti skid and abs light would come momentarily, braking was fine and then the scraping sound again.

any thoughts or similar situation out there



here is a shot of the drop outs with RF wheel stationary :

a neighbor asked me if i could help him ou twith an ABS fault code : C1222-20 " no connection between ABS module and VSS". In as much as ABS module is difficult to reach, i decided to scope the RF vss. though the wheel was difficult to turn i was able to get an AC signal with KOEO with vehicle stationary. however as i left the signal going, i noticed some drop outs. could this be a module problem? i drove it around the block and when i step on the brakes, it makes that grinding sound; but as soon as the anti skid and abs light would come momentarily, braking was fine and then the scraping sound again.

any thoughts or similar situation out there...

i hope im succesful in uploading these screen shots...

Your code description sounded a bit odd, so I went and checked it against SI. C1222 - Wheel Speed Mismatch:

When the vehicle speed exceeds 20 km/h (12 mph), if the ABS module detects a difference between wheel speed sensor signals, DTC C1222 will be set. DTC C1222 can also be set by damaged tone rings, mismatched wheel and/or tire sizes or driving the vehicle on one or more deflated tires.

Where were your scope leads connected in your screenshots? I see an 11-ish volt signal in red, but where is blue connected?

Because these are active wheel speed sensors (not variable reluctance), and active WSS systems are usually pretty good at finding circuit issues on their own, I'm gonna say it's probably not a module problem. More likely there's a physical problem. Missing tone wheel, smoked wheel bearing, air gap, like that.

vehicle tires are all same size n brand. and same tire pressure. that was the first thing i looked at.

I probed the RF sensor Hi gray/vio wire and showed near battery voltage and AC coupled the other RF sensor low colored violet wire which exhibited a square wave (i had difficulty turning the wheel that is why i had only had a single pattern. but as i kept the scope running, i noticed these drop outs...the same thing happened on the LF wheel speed sensor.

Hi Tyler...just an update. This vehicle I find weird. When I accelerate beyond 40km/hr, the traction and abs lights come on and braking seem fine, no scraping sound heard and scanned speed sensor graphed normal - inceasing when accelerating and decreasing at decel; but dash indicate the need to service the traction system. Also, it is very unusual when jacking up both front end of the vehicle, both left and right front wheels are extremely hard to rotate; Im thinking bearing problem.

Hooked my scanner and vehicle speed sensor read normal

robert.lesaca wrote:

I probed the RF sensor Hi gray/vio wire and showed near battery voltage and AC coupled the other RF sensor low colored violet wire which exhibited a square wave (i had difficulty turning the wheel that is why i had only had a single pattern. but as i kept the scope running, i noticed these drop outs...the same thing happened on the LF wheel speed sensor.

I'm honestly not sure what the active wheel speed signal is going to look like on an AC coupled signal. I'd be tempted to put those signals aside for now.

Hi Tyler...just an update. This vehicle I find weird. When I accelerate beyond 40km/hr, the traction and abs lights come on and braking seem fine

This is probably because the C1222 is setting as Current during that drive cycle, and the ABS gets disabled. That's your scraping sound - the ABS running in response to a (perceived) locked up wheel.

Hooked my scanner and vehicle speed sensor read normal

This is not a vehicle speed sensor problem. This is an issue with a difference in wheel speed sensor signals. You'll need to graph all four wheel speed sensors and look for any erratic behavior to narrow down your search.

Also, it is very unusual when jacking up both front end of the vehicle, both left and right front wheels are extremely hard to rotate; Im thinking bearing problem.

Wouldn't be the first MKT/Explorer/Flex with a bad wheel bearing. :lol: But I don't normally find that failing wheel bearings cause the wheels to be difficult to turn... Unless they're so loose that the rotor is digging into the brake caliper bracket (and causing an air gap problem with the wheel speed sensor).

Are either of the front wheel bearings loose? Do both of the front wheel speed sensor tone wheels pass a visual inspection?

I went to focus on the fuses/relays at the engine compartment and underneath the dash. Corrosion, missing A/C clutch relay as well as cracks on 2 relay housing is quite noticeable, indicating someone was tinkered around this vehicle.

A bigger surprise is under the dash smart junction box where a row of fuses (lower most row in the picture) exhibited ground instead of power as indicated by my power probe; the rest showed power !

I intend to show this to the owner later today and recommend to bring it for repairs in a shop...

Post a screen shot of the 4 speed sensors graphed?

Hello Cheryl ...sorry for the late reply. I am using Topdon Phoenix Elite that has the ability of showing only one general PID for all 4 speed sensors instead of 4 separate ones. Topdon wants me to send them a video of the record I did for their engineers to see. But honestly I dont think it will be of help - it only shows an incease in slope as I accelerate and decrease as I decel and nothing more.

You sure that’s not the vehicle speed sensor? Does it say left right etc wheel speed sensor on the pids