The Rev C install on the 2017-2019 GM 6.6L L5P is straightforward, but the details matter. This Banks Derringer Tuner setup uses just two top-side engine connections: the TMAP sensor and the fuel rail pressure sensor. From there, the important part is finishing the system correctly. The termination cap at the Derringer and the termination jumper at the Banks iDash Pro tell the electronics where the circuit ends. Leave either one out and you can get odd behavior. Proper connector alignment matters too, because the pins are keyed and gold-plated. Once the harness is tied down, routed clear of moving parts, and the starter and OBD cables are run cleanly into the cab, you end up with a solid installation that’s easy to service and ready to use.
This installation walkthrough is specifically for the Banks Derringer for the L5P using the Rev C, or version C, wiring harness. Before starting, the video instructs owners to inspect the harness version. If the harness is version B, the procedure is different and the owner should stop and use the owner's manual for that version. Only version C continues with the process shown here.
The video begins by identifying the main Derringer system components and explaining the role of the termination pieces. If the Derringer kit includes a switch, the gray termination cap is used. If the kit includes an iDash, the black termination cap is used instead. Banks emphasizes that the termination cap and the termination jumper on the back of the iDash are both active electronic components, not simple plugs. They tell the system where the circuit ends, much like the ends of a network. If either the termination cap or the termination jumper is omitted, the system may behave unpredictably.
Before working with the truck's electronics, Banks recommends disconnecting the batteries. On the L5P, that means disconnecting the negative terminal on both batteries. With power removed, the Rev C harness installation only requires connections at two locations on top of the engine: the TMAP sensor, which is the temperature manifold absolute pressure sensor, and the FRP sensor, the fuel rail pressure sensor.
To disconnect each factory connector, the gray locking clip on top of the plug is first slid back slightly, about one-eighth of an inch. Once the lock is released, the connector can be pinched and pulled free. The video stresses pulling on the connector body rather than tugging on the wires, and notes that a small amount of wiggling may be needed.
After the factory TMAP and FRP connectors are unplugged, the Derringer harness is connected inline. The lead marked for the MAP sensor is attached to the corresponding TMAP sensor connections, and the FRP lead is connected in the same way at the fuel rail pressure sensor. Once both inline connections are made, the locking clips should be pushed back into place on the plugs.
The harness is then secured with zip ties. Banks recommends tying the connectors down firmly and routing the harness across the top of the engine so it cannot contact moving parts. From there, the harness is routed toward the battery area and ultimately to the crossmember above the battery, where the Derringer module will be mounted.
With the harness in place, the Derringer module is connected to it and the correct termination cap is installed. The same rule applies here: gray for the switch kit, black for an iDash-equipped system. The starter cable is then attached to the opposite side of the Derringer.
The video cautions against forcing the cable into the module because the connector uses gold-plated pins that can be bent if misaligned. Both the Derringer and the mating connectors have locating tabs, so they only fit one way. Once aligned correctly, the connector slides in smoothly and the locking mechanism can be turned to secure it.
The Derringer module is mounted on the crossmember above the battery with the LED facing toward the front of the vehicle so it remains visible when the hood is open. The housing includes openings that allow zip ties to pass through for a secure mount. After mounting, the installer should make one final inspection of the harness routing to confirm that it clears moving components, the battery tray, and any other parts that may need to be removed or serviced later.
The starter cable must then be routed from the engine bay into the cab through the large firewall grommet. The video notes that this can be done alone, but it is easier with a second person inside the truck to help locate and pull the cable through. Two routing methods are shown. One option is to cut a hole in the grommet and use a coat hanger or similar fish tool. The other, demonstrated in the video, is to push the grommet down and route the cable around it instead.
Inside the cab, the installer removes the plastic panel above the driver's left foot. This panel is retained by one clip on the left and two on the right. Once the clips are released, the black cover pulls outward and drops down, allowing access behind it. The starter cable can then be found by feel and carefully pulled through, with a helper feeding slack from the engine side if needed.
After the cable is pulled into the cab, attention returns briefly to the engine bay to verify that enough slack remains for the Derringer to stay properly mounted on the crossmember. The installation then continues inside the truck.
The side dash panel that covers the fuse block is removed by carefully prying it away from its retaining clips. The starter cable is routed up and over the emergency brake, then guided up the side of the dash toward the A-pillar or wherever the iDash will be mounted. The OBD cable is then plugged in and routed along the same path. Banks recommends bundling the OBD cable and starter cable together with zip ties, then looping and securing any excess cable and storing it behind the side panel.
If the Derringer kit includes an iDash and a pillar mount, the factory A-pillar trim must be removed. This is done by taking off the two plastic covers that conceal the 10 mm bolts. A screwdriver or plastic trim tool can be used, but the video advises care to avoid permanently marking the stock pillar in case it will be reinstalled later. Once the bolts are removed, the pillar is pulled toward the steering wheel and then upward.
A small white plastic nutsert from the pillar assembly must be retained and not lost or broken. It is inserted into the center of the elongated slot at the top of the replacement pillar. The wires are then fed through the gauge opening, leaving about four inches exposed. The pillar is pushed down into place at the dash, and the weatherstripping is pulled out and around the pillar to help hold it while the fastener is started.
The mounting screw is then threaded into the plastic nutsert by hand first, then snugged with a screwdriver. The video specifically warns not to overtighten it because the nutsert is plastic and can break if excessive force is used.
The iDash is installed only after confirming that the termination plug is present in the back of the gauge. In systems with multiple iDash units, only the last iDash in the chain should contain the termination plug. With two iDashes, the plug belongs in the secondary unit. With three iDashes, it should be installed only in the third unit.
Before inserting the gauge into the pillar mount, the two white plastic nuts and the black plastic spacer on the back of the iDash are removed because they are not needed for this installation. The wires are connected, and the iDash is carefully slipped into the pillar opening, where it should be held in place by friction.
To finish the job, the black under-dash cover is snapped back into place and the installer returns to the engine bay to reconnect both batteries. The video closes by directing users to Banks' iDash tutorial resources for a full explanation of the gauge's functions, then notes that the truck is ready to drive with the Derringer installed.