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Intermittent "Service Rear Park Sensors" warning?

Tiny
SUGARRAY40
  • MEMBER
  • 2015 RAM 2500
  • 6.4L
  • V8
  • 4WD
  • AUTOMATIC
  • 140,000 MILES
For approximately 1-2 months I have been getting a warning from Service Rear Park sensors. This turns off the "beep" of the rear sensors. Then it will "ding" and start working. This seems to be more frequent off and on when it is cold and at times, I think it is related to taking off from a stop or park and when braking to a stop at a light or stop sign.

My local dealer (different from the previous ABS sensor) told me because my bumper was dented and the sensor was facing toward the midline of the truck, it was causing ghost readings between the 2 middle sensors. As such, they wanted me to put in a new bumper, which I declined at >$800 for the bumper and plastic top then new sensor housings and installation.

I "massaged" my bumper and to my eye the sensor is facing straight back now, but his has not improved the intermittent warning

My question: Could this be related to the main harness coming from the 42-pin connector in the driver's front wheel? My reasoning is that I've already had a problem from this harness with my ABS sensor and think "rubbing" will continue and compound over time.

If someone would share the wiring diagram, it would be greatly appreciated.
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Wednesday, February 28th, 2024 AT 11:24 AM

25 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,244 POSTS
Hi,

There is a park assist module that controls the different sensors at the rear. The Module is in the vehicle behind the left kick panel.

If you look at pic 1, it shows the kick panel being removed. Pic 2 shows the module itself.

There are two connectors on the module. I attached a pin out of them below as well. This leads me to a question. Did they tell you which sensor was the problem? There are a few. Also, were any trouble codes provided?

Let me know.

Joe

See pics below. Note the colors of the connectors. C1 is black and C2 is gray.
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Wednesday, February 28th, 2024 AT 7:46 PM
Tiny
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The work order states stored code for sensor 11, cleared codes.

Which sensor is sensor 11?
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Thursday, February 29th, 2024 AT 12:08 PM
Tiny
JACOBANDNICKOLAS
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Hi,

I attached a pic below showing sensor 11. It is on the driver's side.

Check the wiring to the sensor to see if there is any evidence of damage.

Let me know.

Joe

See pic below.
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Thursday, February 29th, 2024 AT 8:21 PM
Tiny
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I took that harness off and there is no evidence of wear. I checked every line for continuity and had good continuity from each sensor connector back to the main 6 pin connector.
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Friday, March 1st, 2024 AT 5:03 AM
Tiny
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I have also rotated a new Bosch sensor from AutoZone through each sensor position without resolution.
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Friday, March 1st, 2024 AT 5:04 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Check one of the working sensor connectors to determine if there is a 5v power reference. If there is, check connector 11.

For some reason I'm not finding the connector view at the sensor. That's why I'm suggesting doing it this way.

Let me know.

Joe
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Friday, March 1st, 2024 AT 7:39 PM
Tiny
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When I probe ground to power wire I get 4.1 volts at the 10 and 11 sensor harness. When I probe ground and signal wire I get 8.7 volts.
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Tuesday, March 5th, 2024 AT 3:23 PM
Tiny
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The signal wire shouldn't have that much power. It sounds like there could be a short to power.

The 4.1v is a little on the low side, but I would think it would still start.

Let me know. Check to make sure the signal wire isn't damaged. Also, I am assuming this test was done with the engine off.

Take care,

Joe
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Tuesday, March 5th, 2024 AT 7:38 PM
Tiny
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The engine was off but ignition on Run. I didn’t figure there’d be power without the key on Run.

Okay, I’ll open the loom and check the wire.
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Tuesday, March 5th, 2024 AT 8:13 PM
Tiny
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The wires all look good. I don’t think I need to take down the power and ground connections since it seemed to be just 1 sensor.
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Friday, March 8th, 2024 AT 12:53 PM
Tiny
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When I check resistance across the pins on the sensor I get these OHM readings: sensor 11 - signal to grey/orange 50.5 ohm, signal to grey/blue 174.2 ohm, grey/orange to grey/blue 131.7 ohm.

I then checked Bosch sensor from AutoZone with readings of 50.9, 184.1, 137.8 ohms.

Then checked sensor 9 and got 51, 184.2, 135.3 ohms.

I don’t know which wire is ground and which is power. In the attached pic the signal wire is the left pin, grey/blue middle, grey/orange right. I checked each sensor connector, and they are all oriented this way.

Not sure this helps, but it’s more information.
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Friday, March 8th, 2024 AT 1:27 PM
Tiny
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When I check resistance across the pins on the sensor I get these OHM readings: sensor 11 - signal to grey/orange 50.5 ohm, signal to grey/blue 174.2 ohm, grey/orange to grey/blue 131.7 ohm.

I then checked Bosch sensor from Autozone with readings of 50.9, 184.1, 137.8 ohms

Then checked sensor 9 and got 51, 184.2, 135.3 ohms.

I don’t know which wire is ground and which is power. In the attached pic the signal wire is the left pin, grey/blue middle, grey/orange right. I checked each sensor connector and they are all oriented this way.

Not sure this helps, but it’s more information.
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Friday, March 8th, 2024 AT 4:36 PM
Tiny
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I checked continuity from rear 6 pin connector for the sensor harness to the control module and had good continuity through all 6 lines.
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Friday, March 8th, 2024 AT 4:37 PM
Tiny
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Hi,

If you look below, I attached a pic of the connector and highlighted the sensor ground pin. Take a look and let me know if that helps.

Joe

See pic below.
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Friday, March 8th, 2024 AT 8:12 PM
Tiny
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It’s help confirm ground is the center pin.

I drove a 40-mile round trip this morning and no alert. It is raining here and it's 45 degrees. I’ll just have to see if all that fiddling made a difference, but I can’t find a concern with a sensor or the sensor harness. Wiring seems to be intact to the park sensor module too. If it picks up again, I guess, I’ll try to find someone I can swap modules with and see if it makes a difference.
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Saturday, March 9th, 2024 AT 7:01 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Actually, if you are able to find one you can use for testing, that would be a great idea. As far as the weather is concerned, it sounds like you live next door to me. LOL

Let me know if things change or continue working properly.

Take care,

Joe
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Saturday, March 9th, 2024 AT 5:22 PM
Tiny
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Thank you for all your help! And my brother has a 2500 I can swap out modules if I need too.
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Sunday, March 10th, 2024 AT 6:10 AM
Tiny
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So, I didn’t even need to drive today. Service park sensors warning on as soon as I got in the truck after a remote start. It is 32-34 degrees with snow flurries.

Does the colder temperature point to a sensor or the module as being more likely?
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Sunday, March 10th, 2024 AT 12:01 PM
Tiny
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Hi,

We have the same weather. LOL I'm not sure what is happening as far as the ECT. As far as the parking sensor is concerned, if you have access to another module, give it a try and see if that eliminates the problem.

Let me know.

Joe
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Sunday, March 10th, 2024 AT 8:13 PM
Tiny
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So, I checked the sensor “clicking” today and sensor 11 was clicking but significantly less than the other 3. Also, I didn’t get the proximity alert from sensor 11 like the other 3 as well. So, I swapped out 11 for the Bosch sensor from AutoZone. Short drive to town, 3 miles, and no problems. We’ll see in the morning when it’s supposed to be 25-ish degrees.
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Sunday, March 10th, 2024 AT 8:35 PM

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