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Intermittent left rear ABS sensor not sending signal?

Tiny
SUGARRAY40
  • MEMBER
  • 2015 RAM 2500
  • 6.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 125,300 MILES
I began having intermittent ABS, traction control warning lights and inability to use cruise control or 4wd while driving on a gravel road. Somewhat bumpy, but typical road here in WV. Went to my local, preferred mechanic. Scan tool indicated the left rear ABS sensor was bad, so I replaced it. Did not improve symptoms so I had the shop repair it. But the symptoms still persist with a new sensor. I believe there is a break in the wire along the way. I have been unable to find the wiring diagram for the sensor so I can test the line and find the area of concern.

Can anyone post the diagram or link, please?
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Monday, April 17th, 2023 AT 8:12 AM

39 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,574 POSTS
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.
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Monday, April 17th, 2023 AT 4:49 PM
Tiny
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Thank you Steve.
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Tuesday, April 18th, 2023 AT 4:58 AM
Tiny
STEVE W.
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You're welcome. Please update us on what you find.
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Tuesday, April 18th, 2023 AT 5:26 AM
Tiny
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Where is the ABS module?
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Sunday, May 7th, 2023 AT 2:24 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
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.
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Tuesday, May 9th, 2023 AT 8:11 PM
Tiny
STEVE W.
  • MECHANIC
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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.
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Tuesday, May 9th, 2023 AT 8:26 PM
Tiny
SUGARRAY40
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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.
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Thursday, May 11th, 2023 AT 5:03 AM
Tiny
STEVE W.
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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.
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Thursday, May 11th, 2023 AT 9:14 AM
Tiny
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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.
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Friday, May 12th, 2023 AT 2:56 AM
Tiny
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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.
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Friday, May 12th, 2023 AT 2:56 AM
Tiny
STEVE W.
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Sounds like a plan.
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Friday, May 12th, 2023 AT 9:06 AM
Tiny
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Didn’t help.
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Saturday, May 13th, 2023 AT 7:23 AM
Tiny
STEVE W.
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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.
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Saturday, May 13th, 2023 AT 9:10 AM
Tiny
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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.
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Saturday, May 13th, 2023 AT 9:42 AM
Tiny
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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.
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Saturday, May 13th, 2023 AT 9:43 AM
Tiny
STEVE W.
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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.
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Saturday, May 13th, 2023 AT 6:43 PM
Tiny
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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?
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Sunday, June 18th, 2023 AT 6:17 PM
Tiny
STEVE W.
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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.
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Sunday, June 18th, 2023 AT 8:43 PM
Tiny
JACOBANDNICKOLAS
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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
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Sunday, June 18th, 2023 AT 8:44 PM
Tiny
SUGARRAY40
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  • 36 POSTS
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.
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Monday, June 19th, 2023 AT 12:47 PM

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