I have confirmed that you can use an ABS Module and HCU from another vehicle. I was able to activate ACC on a 2021 Bighorn using a donor ABS/HCU assembly (both parts) from a 2019 Limited with the Advanced Safety Group which includes Adaptive Cruise Control w/Stop and Go. I recommend getting the VIN from the donor vehicle and verifying that it does in fact have Adaptive Cruise Control w/Stop and Go using the FCA window sticker lookup tool. Of the two I was able to find for sale on a popular website, one was listed with the wrong part number and was not the correct part. Fortunately, I caught it before I bought and installed it.
I used AlfaOBD 2.3.6.0 on Windows with an OBDLink EX USB interface an inexpensive 12+8 FCA SGW module bypass cable. I assume other combinations will work but can't confirm.
The additional step required to get past the VIN mismatch fault is to run “Reset VIN values” using AlfaOBD. It has been previously been confirmed to work with older 1500 Rams and HD Rams, and I can confirm that it also works with a 2021 Ram 1500 DT.
Steps:
- Connect to function “ABS” and ECU “ABS Bosch/Continental/Teves/TRW PowerNet: DT MY2019+ PowerNet” using AlfaOBD.
- Read the system ID and System Status under Status/Faults and save the log for future reference if needed (not required, but a good idea).
- Disconnect and turn of ignition.
- Disconnect the battery.
- Remove old ABS/HCU assembly and install the donor assembly. Be prepared to deal with about 1 quart of spilled brake fluid, most of which will come out of line on the back of the HCU closest the right fender.
- Install donor ABS/HCU assembly.
- Perform a base brake system bleed (using any of the old school methods).
- Connect battery.
- Connect to Function “ABS” and ECU “ABS Bosch/Continental/Teves/TRW PowerNet: DT MY2019+ PowerNet” using AlfaOBD
- Read System ID and System Status and save the log again.
- Run “Reset VIN Values” under Active Diagnostic. When I ran this is never returned a process complete status but it worked. I waited about five minutes.
- Power off ignition and wait a couple minutes for the power off delay to expire.
- Connect to Function “ABS” and ECU “ABS Bosch/Continental/Teves/TRW PowerNet: DT MY2019+ PowerNet” using AlfaOBD
- Read System ID again. Verify that the value for VIN current all question marks. If not, repeat. The ABS ECU initialization will not work until the VIN current value is properly cleared.
- Perform the ABS module bleed procedure using AlfaOBD (AlfaOBD will guide you).
- I'm pretty sure the factory service manual says to run a base system bleed on the brakes again after the ABS bleed, but I can't confirm. Other than a little more time, it can't hurt.
- Run static ECU initialization
- Run Longitudinal acceleration sensor calibration. I had to disconnect, go to advanced mode, uncheck verify ECU, and connect to RAM 1500/2500/3500/4500/5500: MY2013+ PowerNet to get this to work. The option under DT MY2019+ of “Longitudinal and Lateral sensor calibration fails”. I only used the 2013+ option for this one step.
- Clear codes and cycle ignition
- Run clearing Rolls Information
- Run Inlet Valve Calibration
- Run Pilot Valve Calibration
- Run Sensor Cluster Calibration
- Run Brake Pedal Calibration
When this was all done, I only had one remaining error which was the EPB error. This cleared when I engaged and released the parking brake and cycled the ignition one time.
Note that the ABS module will retain the VIN from the original vehicle under the VIN original value. Only the VIN current value needs to match the current vehicle.
Much thanks to all those that did the hard work to figure this stuff out!
One step closer to installing a Comma 3!
