Intermittent left rear ABS sensor not sending signal?

The two wires from the sensor go to the ABS module with a single connection in the harness. The easiest way to test it would be to go to the ABS module and find the dark green with yellow stripe and dark green with gray stripe at pins 41 and 42. Then unplug the sensor and short the terminals and test at the ABS end for continuity. The other way would be if you have a scan tool that can read live ABS data and if you have that you could unplug both rear sensors and jump the right signal to the left side and see if you can now see the speed show up on the left side when you spin the right wheel.
Attached is the wiring for those sensors and the inline connector.

Thank you Steve.

You're welcome. Please update us on what you find.

Where is the ABS module?

Hi,

I noticed you haven't been contacted for a couple of days. Have you been able to make any progress?

As far as the module, I attached a pic below to help you locate it. Let me know if that helps or if you have questions.

Take care,

Joe

See pic below.

The ABS module is located under the fender behind the liner on the driver's side attached to the hydraulic brake module that has all the brake lines coming in and out of it. To get to it you remove the wheel and then the fender liner. The modules are above the spring mount. You can see it from the engine compartment but not really get to it. I take it that jumping the sensors still showed a bad left sensor? Hope it's just a bad harness or connection.

What I have found/what has happened:

I took my truck to my local Ram dealer who obtained a new Mopar ABS sensor and replaced my aftermarket sensor and said all was well. I drove for 15 miles and error returned.

I tested the line from the sensor connector to the ABS module connector and found good continuity on leg 41 but no continuity on leg 42.

Now I'm at a loss as I cannot find the 12-pin connector. My belief is this connector is between the left rear sensor connector and the front ABS connector. I am hopeful this will shorten the wiring I need to replace to try to correct my problem. I have a new 2 wire connector to replace at the left rear if needed.

Any further direction would be greatly appreciated.

That harness connection is under the truck below the driver's seat area as shown in the image below. If they replaced the sensor and the error cleared but returned, I would suspect it's the connector where the sensor plugs in, the ones Chrysler uses have a bad habit of failing right at the crimp where the wire enters the metal terminal. As you know where the terminal on the ABS module is you might want to try a puncture test. Take a sewing needle or similar and poke it through the insulation an inch or two up the wire at the sensor end, now test for continuity. If it's okay now, it's the connector. If you still have nothing dig out the inline connector and check there. Use a drop or two of liquid tape or similar to seal the hole you poked in the wire. Or if you replace the connector, be sure to cut the wire above the hole.

So, I tested the 2 separate runs. From the rear connector to the 12-pin connector and from the 12 pin to the control unit. Both runs had continuity. I’m going to replace the rear connector as suggested and see how this affects things. I hope to get to this today. I’ll keep you updated.

So, I tested the 2 separate runs. From the rear connector to the 12 pin connector and from the 12 pin to the control unit. Both runs had continuity. I’m going to replace the rear connector as suggested and see how this affects things. I hope to get to this today. I’ll keep you updated.

Sounds like a plan.

Didn’t help.

Do you have a scan tool that can read the wheel speeds that the ABS module sees from the sensors? You said you didn't have continuity on leg 42, has that changed? If not, then you need to determine where it's broken. If it's now good and you don't show a speed jumper the working signal to it or inject a sine wave signal and see if you get anything.

I do not have a scan tool.

I did not have continuity on leg 42 of the whole line going from the left rear ABS sensor connector back to the main harness at the ABS control module by the shock tower.

I then checked continuity from the rear connector to the 12-pin connector by the drive door and had continuity on both legs and again continuity on both legs from the 12-pin connector to the main harness by the shock tower.

I changed the rear connector yesterday in the hopes this would fix the intermittent problem.
It did not, still have the intermittent interruption of signal.

I then checked today for power at the rear connector when the warning lights were illuminated on the dash and had power on the + leg and I believe, by my use of the multimeter, good ground on the - leg. I believe this means the entire run of both 41 and 42 are good.

I have you all helping and a good friend who is a heavy equipment mechanic helping me via phone.

I have been to my local shop I use and to my local Ram dealer, neither of which solved the problem. I am reluctant to spend money paying them to tackle it again.

I believe I'll have to just get to my buddy's and work with him to check everything. I've been avoiding this as it is turkey season, and he is 1.5 hours away.

Easier test. Go to the ABS module, unplug the connector. Take a jumper wire and connect the two pins together in the rear where the sensor plugs in, go to the abs end, put battery voltage on one wire and use a test light to see if that power is going down the wire, across the jumper and back up to the light. If it isn't take the jumper off of one wire and connect it to ground at the axle end. Now connect the test light to battery power, touch the pin for the circuit you jumped. Light lights? Circuit okay, switch to the other wire. Same thing. Don't use a meter though, they can tell you it's a good circuit even if there is only a single strand of wire that is good. The test light will apply a bit of load and see if it can carry some current.

Update:

I took a vacation for 2 weeks and sent my truck to a different local shop that I have been told the owner worked at 2 Ram dealers before opening his own shop.

He stated he found a rubbed through wire in the front wheel well but is unsure if it is the ABS circuit. He repaired this and stated he drove the truck on "rough" roads and didn't have any codes, warnings, or lights.

I paid and left the shop and when I put in reverse my dash told me I had a backup light out.
No big deal, I have 128,500 miles on the truck. Then within 4 miles after going over a bridge on the interstate at 76 mph the traction control light flashed, cruise stopped. I was able to resume the cruise and drove another 2 miles and fueled up. When I started the truck to head home my dash told me in addition to the backup light my right brake/turn light was out. Again, didn't think much of this given the age of the truck. So, I went to Auto Zone and picked up replacement bulbs and when I put the truck in reverse with key in run the right light was out. When I took the bulb out, the wire was intact. I used a jump box to put 12 volts to it and it lit right up. So, I became suspicious that there is now a problem in this circuit. I have LED brake lights so I can't replace them and have to buy a new taillight assembly, $450, but I do not believe it is really out.

While driving around town, 25-35 MPH, the same intermittent problems occurred and now a new problem with the rear park sensors. I'll post the video.

So, I still do not have my problem fixed and have 2 new problems.

My plan is to contact the most recent mechanic and have him tackle it again.

Thoughts?

The taillight issue could be the ground, it is common between all the lights and it runs all the way up the truck and to a ground point 914 in the left side of the engine compartment. Likely in the same harness where the other wire was. An easy test, black wire is the ground, use a pin to push through the black wire, connect the pin to ground, light works? Bad ground wire, Remove pin and seal puncture with liquid tape. Chrysler is well known for bad grounds that look perfect. That same ground point connects to these other items as well. I would have them look at that same harness again then the ground. It would not be the first-time multiple issues were ground related.

Hi,

While I was watching the video, I noticed once or twice it appeared the information center glitched on and off. Did that happen or is it because it's a video?

If I had to guess, there is an internal fault with the ABS module. Let's see if Steve has any other ideas.

I'll watch to see what he says. Also, let us know if the shop told you what color the wire was that was repaired.

Take care,

Joe

Yes, it will now flash between the warning and the normal “cluster” I use.

I too think it’s an internal fault with the ABS module as there are multiple similar concerns in talk forums that have been fixed with a new ABS module, but it’s hard to put $600 in when all other things haven’t been ruled out.

Now I also have a check engine light that is an open thermostat.

Hi,

Check the connectors at the ABS module. Make sure there is nothing that could be causing an intermittent condition. Also, let me know what code you find.

Take care,

joe

Thermostat rationality code.

Hi,

Okay, I was hoping it would be something that in some way affected the ABS.

Regardless, let me know.

Joe

That is a common code on Chryslers of that vintage Seems like 2010 up to about 2018 have thermostat issues, the usual problem is that they stick open just enough that the engine doesn't warm up fast enough.
That won't affect the ABS though. As for the glitch in the video, does that also appear off camera? I've seen some really strange things when video capturing the PWM dash displays in vehicles. If you see it in person, then it may be an issue. As for the ABS issue, I would go to the unit itself. Unplug it and use a tool to release the wires for both rear sensors. Now swap them so that the right side (without a problem) is connected to the right and the left side is connected to the right side. Because you didn't have an issue on the right side before this swap right at the module would tell you for sure if it's the module or wiring. My earlier reply shows both sensors and the wires for them. The other option would be to use a scope and see what the actual signal from the sensor is doing.

Steve,

Yes, there is a "glitch" on the dash. But it is accompanied by a dinging when the rear park sensors are "off". This is new, it was just dinging 1 time and then telling me the sensors are off. It only has done this off/on "glitch" 2 times.

Should I replace the thermostat?

I have another appointment with my local dealer on Monday. I have all the history and videos to show them. Hoping they can figure it out.

He didn’t tell me what color wire he fixed.

Replace the thermostat and bleed the system will take care of that code normally. The double tones may be to tell you that the sensors are off and that there is a code stored. Hard to say if the rear sensors are related to the other problems or if it's a typical bad sensor. A quick check on the sensors is to listen to them. Block a wheel, turn the key on and put the truck in reverse to be sure they are on. Now go back and listen at each one, they will make a faint clicking if they are working, if all but one is clicking it's a bad sensor, if none are clicking it's more likely the module that controls them.

I’ve flushed my heater core and replaced the coolant but struggled some to bleed it. Is there a link to a process? I have a closed system.

The OE method is to use a vac-u-fill to pull the air out and fill it. What you might try would be to fill it, then rev the engine a bit and let it warm up. Then once it warms up let it cool off. Top it up and repeat. It may take a few runs to get all the air out.

Due to rain, I have been unable to try any of the evaluations you have recommended. I have tendered my truck to my local dealer to hopefully complete these repairs.

Please let us know what they find.

Update:

1) Thermostat replaced and no further problems

2) Right taillight and back up light - found the "repaired" wire which the dealer stated was only taped and not repaired. Repaired this broken wire free of charge and taillight works as does back up light. On a side note, the original call back about the backup light was that "I needed a new bulb" and I had to correct them that I checked the bulb, and it was intact.

3) Rear Park sensors - those intermittent warnings have resolved once the above wire was repaired.

4) ABS sensor - through their testing the line, the sensor, driving, watching the active and stored codes they believe I have to replace my rear axle housing as this will give me a new bolt hole to secure the sensor. They state the sensor is not secure nor square with the speed ring and thus the bumps cause erratic reading and codes. They found no HCU or ABS module codes. This is a quoted $4500 repair on an 8-year-old truck with 129,000 miles.

My response is to have them check the original sensor I had in when this all began, I still have this sensor. If it is good, I believe I'll take a chance and still change the HCU and ABS module. I am basing this on all the reports I have read on talk forums with trucks just like mine having the same issue => no HCU/ABS codes, many sensor changes, new line run to the sensor, and no fix until these modules are changed. I realize it is a risk but I believe its a better risk as I cannot get the dealer to guarantee their recommendation will be the fix.

Any and all thoughts are welcome. I am ignorant but trying to assimilate all the information I am getting.

The ABS sensor hole thing doesn't really make sense, if that was the issue why hasn't it been a problem until now? I know rust jacking can be a problem on them but for that you stuff a plug in the hole and use a coarse file to remove the rust and smooth them up. Then you use a T plug that just slips into the hole to verify that the surface is at a right angle and in line to the tone ring. Easy enough to check that out using a simple method, Take a wood dowel that fits in the sensor hole, put marker on the end of it and insert it into the hole, now rotate the axle and push the dowel in to scrub the end on the ring, pull it out and see what is going on. Also feel the dowel as the axle rotates, it should stay at the same distance as the ring rotates, if you can feel it moving up and down like the ring isn't actually round then you might need to replace some parts but not the housing.

It's not the sensor hole, it's the bolt hole. They think since it's "off" it makes the sensor sit crooked and move in the sensor hole.

Still the same thing as above. The sensor centers itself in the hole and the bolt isn't going to move it around. Easy way to tell, remove the bolt, does the sensor suddenly move around? Try the test above. I would actually be more concerned about a cracked reluctor than the bolt hole, especially when this wasn't an issue for many years, not like you went out and re-machined the housing in the meantime. Still the easiest way to tell would be to put a scope on it and watch the signal. It would show alignment of reluctor failure within about 30 seconds.

Steve, exactly my thoughts but I don’t have the experience to be confident.

I’ve decided I’m going to replace the HCU and ABS module and see what happens.

Please keep us in the loop.

So, I had the dealer check the original Mopar sensor thinking if it worked well then, the original intermittent signal was not from the sensor. They told me the original sensor didn't give signal and as such didn't work. So, I was back to wondering which repair to perform. I decided to replace the ABS module and HCU. My buddy and I could do this and see what happens. I bought the parts yesterday and a scanner from AutoZone that could bleed the ABS. I drove 1.5 hours to my buddy's shop, and we got started. Now, he is a heavy equipment mechanic working on dozers, skidders, loaders, etc., mainly John Deere. We decided to start over, and he called his Snap-On rep who used to be a Mopar mechanic. He told us the problem was the line rubs through somewhere and to run a new line. It is a twisted pair, and my buddy should know how to do this secondary to his experience with John Deere. We decided to check the line to confirm. We put the reader on it and line 41 showed 3.7 ohms/milliohms and line 42 showed 25. My buddy laughed at all the trouble I've had for 3 months. Now, to back up, this confirms what my neighbor and I found early in the process when we couldn't get continuity on line 42 but could on 41. We got confused when we broke the line at the 12-pin connector and had good continuity on each segment of line when they were broken at the connector. So, my buddy twisted a new run, and we spliced it in. All dash lights off. I drove the truck the 1.5 hours home, hitting holes and sparing no speed/line to ensure the truck bounced around. I had no problems. I ran the cruise control, in and out of 4wd and 4 low. Today I went to our favorite swimming hole down a rough logging road and had no problems. Had to use 4wd even. So, a new line seems to have fixed it.

I asked the dealer if they had tested this line and they said yes.

My rear sensor problem and right taillight out warning showed up again after we completed the repair. I tackled this this morning as I had noted the repair by the dealer just before the large connector at the back of the front wheel well yesterday. What I found was one of the locking tabs on that connector was broken. This didn't allow the connection to seat or be square once the lock was engaged. I ensured the connection was in and square and locked. Then I zip tied the top and bottom of the connector careful not to pinch any wires. This alleviated the taillight and rear park sensor problem. I went to my local shop, where I get my tires as well, and they cleared all the stored codes.

So, I believe I have all my problems resolved. I now know more about testing 12-volt connections.

Thank you for all your advice and direction.

Sounds like you got it done. Good job. If the dealership had actually used a scan tool or scope in original testing they should have found the bad wire. That was one of the early tests I mentioned because it's a common issue for failed wires and bad grounds on Chryslers. Has been for 30 years. But you got it fixed.