I installed a Tekonsha Prodigy P2 electronic trailer brake controller in my 2025 Grenadier Trialmaster (equipped with the North America factory Trailer Control Module and 7-pin RV plug). The installation involved fabricating a custom dash mount, pulling a brake signal wire from the Trailer Control Module (TCM) and routing the wiring behind all the various panels between the rear seats and the top left corner of the dash. I chose the Tekonsha over other controllers for several reasons:
- It works well in the mountains on very steep grades and climbing/descending sharp turns.
- The controller has a clear display showing the voltage being applied as well as any status or error messages.
- It includes a button that can be used to temporarily modify the gain setting in three increasing steps when required by an additional load or steep terrain.
- It features a lever that can be used to manually apply the brakes. Unlike the RedArc controller, this feature is immediately available with no fumbling for the right mode in an emergency.
The first task was to figure out a location that would protect the controller during driver entry and exit and be easily accessible while driving. A location on the vertical face of the dash outboard of the steering wheel would make the controller prone to getting hit by feet and shins and it would also be difficult to see while driving. After looking at the Customer Accessory Fitting Instructions in the Ineos Portal, I determined I could keep the controller clear of airbag deployments if I mounted it on top of the dash within the rubber tray at the outer edge.
The rubber tray is held to the dash by three tabs that drop into matching holes. I positioned my base plate over the outer hole so I could use that to route wires without cutting additional holes in the dash. The base plate is made from 1/8" thick aluminum with four # 4-40 x 3/8" press in studs. There's a hole in the middle to allow controller wires to pass into the dash. Here's the back side showing the studs pressed flush:
Here's how the rubber dash tray looks with a cutout for the base plate:
Finally, here's the painted base plate adhered to the dash with 3M VHB double-sided tape and the custom brake controller mount I bent up from 1/16" aluminum. The # 4-40 washers and nuts secure the mount on top of the base plate. I used four nylon washers to space the mount just off the base plate. The aluminum is painted with Rustoleum Painter's Touch Charcoal Gray Satin and it's a pretty good match for the interior colors. The large hole in each part lines up with the hole in the dash and will pass the four brake controller wires. The 3M tape provides a very secure connection to the dash.
Here are several views of the Tekonsha brake controller installed. I'm using some # 8-32 thumb screws to hold the controller in the mount - much cleaner looking and easier to install / remove than screws. The first picture shows exactly what I see from the driver's seat - the controller is below the edge of the vehicle hood and fenders, so it doesn't obstruct my view.
Here's a description of the wiring I installed. After reading all the posts in this thread, I chose to ignore the VIO/ORG wire under the rear seats. Instead, I ran a new 18 AWG (VIO) wire from the TCM BLU/ORG wire in the right rear corner of the vehicle to the rear seat location. (The BLU/ORG wire is pointed out in several posts within this topic, including here.) From there, I used insulated crimp connectors to attach four wires that continued the circuit under the rear seats to the outer edge near the left passenger door. I adopted Tekonsha's wire color scheme from that point forward as follows:
I'm using 14 AWG (RED) for the vehicle brake signal because that's the smallest gauge for which I had the right color on hand, but it could just as well be 18 AWG. For the other wires, I wouldn't go any smaller than the gauges indicated. The WHT wire would probably benefit from being 12 AWG, but there's other ground paths to make up for any lack of capacity and I wanted to keep the wire bundle as small as possible. At the outer edge of the left rear passenger seat, I installed a Deutsch connector before continuing the wiring forward along the door threshhold wire chases.
I encased the four wires in 3/4" fiberglass sleeving to protect them in the chases. There's plenty of room in the chase for something relatively flat - I tried 1/2" corrugated nylon split loom, but it was too bulky. This second run of wire teminates in another Deutsch connector right next to the OBD II connector under the dash with the wires routed up behind the hood release panel. From there, a pigtail from the Tekonsha brake controller connects to the harness. The pigtail is covered in 1/2" fiberglass sleeving until it gets through the dash, then converts to 1/2" nylon split loom.
To route the controller wires from the top of the dash down to near the OBD II connector, I had to relieve a 1/16" thick plastic web right next to an air duct near the hole in the dash. I made a 5/8" diameter hole saw from a 12" long piece of thin-wall tubing and cut a hole in the plastic web. I looked with a borescope camera first - there's nothing immediately behind the web.
My first test of the system resulted in several error messages: TCM error, TSA not available and AEB not available. As soon as I unplugged the brake controller, all the error messages went away. After more research, I followed guidance in this thread from RedArc and Ineos and installed a diode in my brake signal line (VIO). The diode allows current to flow from the TCM to the brake controller but blocks the opposite flow. I had a diode in my parts bin with specs that works just fine:
- Manufacturer: NTE
- Part number: NTE506
- Reverse voltage: 1400 V
- Peak forward current: 35 A
- Max average forward current: 2 A
- Forward voltage drop: 1 V at 1A
If I were sizing a diode from a catalog, I'd probably get something with 600 V reverse voltage and leave the other specs about the same (the 1400 V is an unusually high rating). There should only be milliamps on this circuit but it's nice to have lots of headroom with 2 A on a critical circuit like trailer brakes.
To retrofit the diode into my harness, I built a short harness with Deutsch connectors, inserting it at the harness junction I created under the left rear seat. Here's a few pictures of that:
The cathode band on the diode is pointing towards the brake controller. To install the diode, I crimped bare butt connectors onto the wire and soldered the diode into the open ends. This keeps solder from wicking up the stranded wire and makes replacing the diode (if I ever have to) very easy.
Just to eliminate any doubt, here's a quick diagram of how I wired the Tekonsha:
The diode got rid of all the pertinent error messages. I still get one error message though - when I put the transmission in Reverse, I get a message complaining there are no reverse lights on the trailer (true). I may put a dummy LED on the reverse circuit in the trailer to get rid of this - or not - no big deal. The brakes work great: I can see the controller applying a specific voltage and feel the effect as I ramp up the gain. Manual trailer braking also works, as do all the trailer running lights, brake lights, turn signals and hazard flashers. Success! I've done a few test drives on steep hills around the house and the controller works great . . . very smooth with appropriate modulation.
For fun, here's a pic of the trailer hooked up to the GRINEOS:
Let me know if I can answer any questions.
- It works well in the mountains on very steep grades and climbing/descending sharp turns.
- The controller has a clear display showing the voltage being applied as well as any status or error messages.
- It includes a button that can be used to temporarily modify the gain setting in three increasing steps when required by an additional load or steep terrain.
- It features a lever that can be used to manually apply the brakes. Unlike the RedArc controller, this feature is immediately available with no fumbling for the right mode in an emergency.
The first task was to figure out a location that would protect the controller during driver entry and exit and be easily accessible while driving. A location on the vertical face of the dash outboard of the steering wheel would make the controller prone to getting hit by feet and shins and it would also be difficult to see while driving. After looking at the Customer Accessory Fitting Instructions in the Ineos Portal, I determined I could keep the controller clear of airbag deployments if I mounted it on top of the dash within the rubber tray at the outer edge.
The rubber tray is held to the dash by three tabs that drop into matching holes. I positioned my base plate over the outer hole so I could use that to route wires without cutting additional holes in the dash. The base plate is made from 1/8" thick aluminum with four # 4-40 x 3/8" press in studs. There's a hole in the middle to allow controller wires to pass into the dash. Here's the back side showing the studs pressed flush:
Here's how the rubber dash tray looks with a cutout for the base plate:
Finally, here's the painted base plate adhered to the dash with 3M VHB double-sided tape and the custom brake controller mount I bent up from 1/16" aluminum. The # 4-40 washers and nuts secure the mount on top of the base plate. I used four nylon washers to space the mount just off the base plate. The aluminum is painted with Rustoleum Painter's Touch Charcoal Gray Satin and it's a pretty good match for the interior colors. The large hole in each part lines up with the hole in the dash and will pass the four brake controller wires. The 3M tape provides a very secure connection to the dash.
Here are several views of the Tekonsha brake controller installed. I'm using some # 8-32 thumb screws to hold the controller in the mount - much cleaner looking and easier to install / remove than screws. The first picture shows exactly what I see from the driver's seat - the controller is below the edge of the vehicle hood and fenders, so it doesn't obstruct my view.
Here's a description of the wiring I installed. After reading all the posts in this thread, I chose to ignore the VIO/ORG wire under the rear seats. Instead, I ran a new 18 AWG (VIO) wire from the TCM BLU/ORG wire in the right rear corner of the vehicle to the rear seat location. (The BLU/ORG wire is pointed out in several posts within this topic, including here.) From there, I used insulated crimp connectors to attach four wires that continued the circuit under the rear seats to the outer edge near the left passenger door. I adopted Tekonsha's wire color scheme from that point forward as follows:
Code:
Grenadier Wire Color Function Custom Harness Wire Color & AWG
-------------------- --------------- -------------------------------
YEL/RED 12 V + BLK 12 AWG
BLK 12 V - WHT 14 AWG
VIO (from TCM) veh brake signal RED 14 AWG
GRY 0 to 12 V + BLU 12 AWG
trailer brakeI'm using 14 AWG (RED) for the vehicle brake signal because that's the smallest gauge for which I had the right color on hand, but it could just as well be 18 AWG. For the other wires, I wouldn't go any smaller than the gauges indicated. The WHT wire would probably benefit from being 12 AWG, but there's other ground paths to make up for any lack of capacity and I wanted to keep the wire bundle as small as possible. At the outer edge of the left rear passenger seat, I installed a Deutsch connector before continuing the wiring forward along the door threshhold wire chases.
I encased the four wires in 3/4" fiberglass sleeving to protect them in the chases. There's plenty of room in the chase for something relatively flat - I tried 1/2" corrugated nylon split loom, but it was too bulky. This second run of wire teminates in another Deutsch connector right next to the OBD II connector under the dash with the wires routed up behind the hood release panel. From there, a pigtail from the Tekonsha brake controller connects to the harness. The pigtail is covered in 1/2" fiberglass sleeving until it gets through the dash, then converts to 1/2" nylon split loom.
To route the controller wires from the top of the dash down to near the OBD II connector, I had to relieve a 1/16" thick plastic web right next to an air duct near the hole in the dash. I made a 5/8" diameter hole saw from a 12" long piece of thin-wall tubing and cut a hole in the plastic web. I looked with a borescope camera first - there's nothing immediately behind the web.
My first test of the system resulted in several error messages: TCM error, TSA not available and AEB not available. As soon as I unplugged the brake controller, all the error messages went away. After more research, I followed guidance in this thread from RedArc and Ineos and installed a diode in my brake signal line (VIO). The diode allows current to flow from the TCM to the brake controller but blocks the opposite flow. I had a diode in my parts bin with specs that works just fine:
- Manufacturer: NTE
- Part number: NTE506
- Reverse voltage: 1400 V
- Peak forward current: 35 A
- Max average forward current: 2 A
- Forward voltage drop: 1 V at 1A
If I were sizing a diode from a catalog, I'd probably get something with 600 V reverse voltage and leave the other specs about the same (the 1400 V is an unusually high rating). There should only be milliamps on this circuit but it's nice to have lots of headroom with 2 A on a critical circuit like trailer brakes.
To retrofit the diode into my harness, I built a short harness with Deutsch connectors, inserting it at the harness junction I created under the left rear seat. Here's a few pictures of that:
The cathode band on the diode is pointing towards the brake controller. To install the diode, I crimped bare butt connectors onto the wire and soldered the diode into the open ends. This keeps solder from wicking up the stranded wire and makes replacing the diode (if I ever have to) very easy.
Just to eliminate any doubt, here's a quick diagram of how I wired the Tekonsha:
The diode got rid of all the pertinent error messages. I still get one error message though - when I put the transmission in Reverse, I get a message complaining there are no reverse lights on the trailer (true). I may put a dummy LED on the reverse circuit in the trailer to get rid of this - or not - no big deal. The brakes work great: I can see the controller applying a specific voltage and feel the effect as I ramp up the gain. Manual trailer braking also works, as do all the trailer running lights, brake lights, turn signals and hazard flashers. Success! I've done a few test drives on steep hills around the house and the controller works great . . . very smooth with appropriate modulation.
For fun, here's a pic of the trailer hooked up to the GRINEOS:
Let me know if I can answer any questions.
Last edited:
