2018 Ram 3500
Issues encountered all at once:
- ABS Dash light
- Traction control dash light
- Service ABS system soon message
- OBD Code C003A-2F Right Rear Wheel Speed Sensor – Signal Erratic
- 4WD temporarily unavailable
- Rear backup sensors not available
- Cruise control would turn on, but not set a speed
At first, I replaced the Right Rear Wheel Speed Sensor, no change.
I read on several forums of the Ram ABS issues.
- I tried the easy connector pin verification and wiring from sensors to ABS ECU to ensure contact and continuity, no change.
- I proceeded to replace the ABS HCU with the upgraded part (68243491AB), no change.
- The next direction form the forums was to replace the ABS ECU with upgraded part (68351454AB)
Here is the important part
Prior to buying this costly and hard to find part (back ordered from OEM for over a year), I found a Ram mechanic that would actually talk to me. He suggested I verify the “Tone Ring” was intact.
My initial response was “What’s a Tone Ring”?
It is the toothed gear mounted inside the Parking Brake drum that the Rear Speed Sensor gets its signal from.
Now to replace it, you have to remove that wheel’s hub/brake assembly from the axel,
but you can see a few of the teeth at a time by removing the Speed Sensor, looking through the ~1/2” hole as the wheel is rotated.
When I did this, all the teeth were intact, but the ring was loose. I used a screw driver to touch the Tone Ring, to find that it was not rigidly attached to the wheel’s hub/brake assembly. Therefore it was not rotating at the same speed as the wheel (Erratic Signal!!).
A replacement Tone Ring was ~$150.00. I replaced it myself. I drove the truck for about a mile and all the dash lights, messages and other issues cleared. There was nothing wrong with my ABS system.
I hope this information helps some of you facing similar issues.
NOTE: this repair requires removing that wheel’s hub/brake assembly from the axel. When you do this, the inner seal and outer gasket will need to be replaced.