I had a local mechanic pull the ABS codes I'm getting on my 99 Expedition (4x4). The 1230 code points to a faulty rear wheel ABS sensor but the 1107 code description says "see front drive train". I have been having an issue where my transfer case seems to be engaging whenever I put the vehicle under load (quick accelerations or going up steep grades on the interstate) and it makes a terrible thumping/grinding noise whenever this occurs. I took out the AWD fuse (120) and the noise has gone away but of course I don't have AWD or 4x4 any more. When the mechanic saw the code 1107 "see front drive train" he scanned the transfer case to see see if it had any trouble codes and it didn't. We are at the point of trying to decide if the ABS codes could be causing the issue with the transfer case engaging when it shouldn't. We initially thought the chain in the transfer case was slipping and that could be causing noise I hear but again, there were no trouble codes in the transfer case. I plan to go take the truck into a local guy who specializes in ABS and see if we can get all the malfunctioning sensors replaced and get the ABS light to go away to see if that makes any difference since. Have any of you run across this problem before or have any ideas what it could be?

Thanks

 

From what I've been able to find out, it seems the ABS code "C1107 ABS Function Enabled Input Circuit Failure" is a redundant code for the rear axle speed sensor. That being the case, when the rear sensor is replaced both codes should go away.

 

Thanks for the reply. Looks like I will replace the rear axle ABS speed sensor and see if that gets rid of both codes. I have done some searches on this web site and it looks like I need to remove the spare tire, crawl underneath and the sensor will be sitting on top of the rear differential toward the driver's side? Does this sound correct?

 

Yes it does. Removing the tire is optional but I do recommend it. With the tire out, there is so much more room under there to work. There was so much headroom that I remember sitting upright on my creeper when changing my rear shocks.

 

Thanks to @@alloro for the DTC C1107 information. (For my '99 Exepedition, this was a GEM code, initially all by itself.) But based on the information here and in one other thread, the suspect was this rear ABS / VSS sensor on the top of the differential. And that made some sense, as a few months earlier (two), on this relatively low miles per week vehicle, I had changed the rear limited slip differential fluid and friction control additive, and really cleaned out the diff. (Only the second time in 205K miles, so it was definitely ready again. The impetus to do so was that it was starting to skip a bit in the "front end" on tight turns, which is usually/often the rear limited slip differential not slipping very well, and the clutches are binding. So I replaced the differential fluid and friction control additive, and I also cleaned up the outside of the rear diff cover, and cleaned out all the gunk in the bottom of the diff quite well with a set of lint-free rags.

What I did not do (should have), was pull out the ABS sensor on the top of the diff at that time.

So, I was getting the C1107 GEM code, which alloro suggested might be the rear ABS sensor. Before doing anything, I actually pulled off that sensors connector, and the reseated it again. This had the effect of make the GEM "angrier". It was then throwing C1107 and P0500 codes, which is definitely the ABS sensor. However, I used Forscan to check the GEM's outputs on the front output shaft, and the rear output shaft, and the rear ABS sensor (aka VSS on this vehicle, it doubles in both roles), its a 4x4 with ABS '99, 5.4L Expy. Anyway all those speed outputs look OK. Not awesome, but sensible. At 30mph, the front and rear output shafts matched, and were 2mph faster than the rear ABS sensor output at 30-31 mph, which is where the manual suggests checking it, and that the difference should be 3mph or less, which it was.

So, I removed the old ABS sensor after ordering a new one from Amazon. What I found, was that the ABS sensor was really gunked up with normal differential metal shavings/dust, and this had accumulated on the sensor, which is magnetic. So, I just cleared the sensor with a link-free rag on the sides and end, and wiped off all of the old gear oil/metal dust/metal shavings crude on the sensor. And then reinstalled it. And then cleared the GEM code again. (I had cleared the GEM code twice before, but each time the C1107 had come back again). This time, with the sensor cleaned up with rag of the metal dust/shavings, no more GEM code so far. (And I was performing the Emissions recommended driving sequence after this each time, overnight cold soak, 10 mile freeway at 55MPH, and 20 minutes of 35-39 mph city driving, with 4 stops (I always do 8 stops to make sure the monitor is happy.) This usually hits all the monitors, though this time the EGR is being more difficult. (Probably too warm, will do the next try in the morning....) Anyway, no GEM code this time, after the cleaning.

These magnetic sensors hardly ever really fail, they are pretty dirt simple. But in this case, the sensor was drenched in metal dust/crud and that was throwing off the sensor often enough to **** off the GEM with a C1107 (and later P0500) code, even though the sensor seemed to be giving adquate speed sensor readings the majority of the time.

So, short version, you can try and just pull the rear ABS sensor and clean it, and reinstall it. Be very careful with the lock tabs on the sensor connector, 20 year old plastic is very brittle. The sensor is held in with just one 10mm bolt. You can get at it without removing the spare tire if you have long arms (I have relatively long ones at 6'2") or else you can lower the spare pull it, and raise the spare tray back up, and then have tons of room. But on the 4x4, I can get under there with no creeper and then just reach up from the back side and over the top with one arm, and get at the bolt, and the connector is easiest with both hands, same, way, right hand over the top, left hand from the front side, and gingerly sprint out the lock clips a few mm (1-2) and pull the connector off.

Did the work for me. I will keep the new after-market ABS sensor just in case I have a problem again, but I suspect the old sensor to be fine (so far), and just needing the metail filings crud cleaned off.

Another moral here. Always remove and clean that sensor whenever servicing the rear differential yourself. And ask it to be done when having the rear differential services at a mechanic.,

 

Well, my C1107 came back the next day, so so much for cleaning. I also tried replacing the sensor with a brand new sensor, clearing DTC's (which clear), and driving, and that also has not fixed the issue with the C1107 code. So I am baffled as to where to go. Even the factory service electronic manual seems to be pretty mum on the subject. It lists the C1107 GEM code in the GEM DTC section, but doesn't provide any explanation other the the useless "ABS input" text.

I have tested the GEM outputs with both the sensors, using Forscan. The ABS dymaic readings for the two front (Left and Right) and Rear ABS sensors all agree with each other 100%, at all times and all speeds.

The GEM displayed items of the front output shaft speed and the rear output shaft speed, and the GEM VSS speed (which is the ABS rear sensor speed) are:
The front and rear output shaft speeds always agree with each other 100% of the time. The rear GEM ABS/VSS speed is typically between 1-3 mph lower than the output shaft speeds up to speeds of 30MPH. At about 33/35mps the output shaft speeds, and the GEM rear ABS/VSS speed start to differ by more then 3mph. (And they behave essentially the same with the original rear ABS sensor, and the new one I bought.

The original ABS sensor is a FordMoCo Blue connector Ring ABS sensor.

The replacement ABS sensor (which behaves the same), is an after market Dornan part, that appears to be fit and finish the same, also with blue connector ring.

This is a '99 Expedition 4x4 5.4L with 4R100 transmission. The '99 has no VSS sensor, the rear ABS sensor acts as the VSS sensor input to the GEM, which then does output to the PMC (from the GEM).

Everything is working correctly, but I have this stupid DTC code that I would like to get rid of. Fortunately, this code does not prevent Emissions certification, or cause the MIL to light, its just super aoonying for no reason.

 

@alloro Any idea if the GEM output speeds on the rear sensor (tried two of them), and the front and rear output shafts seem weird. As I said, from 0 to 30mph, the rear sensor is typically 2-3 mph lower than the output shaft sensors. That's true until about 33mph, and then the difference goes up a bit. And the difference grows with increase in speed. Are these supposed to match all the way up, or only be within 3mph at 30mph speed (per the speedometer). And the speedo and the rear ABS sensor seem to be about 3mph off, the speedo is higher, and basically matches the front and rear output shaft sensor values.

Is there any chance this could be some weird tire size or gear ration setting issue. (Like maybe a value flipped in my GEM, and it has the gear ratio or tire size wrong). I think the tire size infomation is stored in the PCM, as is the gear ratio. But not sure if the GEM also maintains either/both of those pieces of information.

Cannot figure it out. All the ABS sensors agree with each other. The factory manual says that at 30mph or higher, the delta should not be more than 3mph. At 30-32 its < 3mph (just barely), but at 33mph the delta in output shaft and rear sensor speed cross over the 3mph delta boundary. Totally frustrating.