Supplemental Information on Trailer Towing and Recreational Vehicle Towing (Dinghy Towing)

This bulletin is being revised to update the parts information to better clarify which UBEC is needed. Please discard Corporate Bulletin Number 07-00-89-021B (Section 00 - General Information).

The purpose of this bulletin is to inform dealers of special procedures necessary when towing a trailer or when towing the vehicle behind a recreational vehicle.

Trailer Weight Information

The following chart shows how much the trailer can weigh, based on the vehicle powertrain combination and whether the vehicle is equipped with Trailer Provision (RPO V92). Retailers should refer customers to the appropriate Owner Manual for important trailering tips, vehicle maintenance, and safety rules before towing a trailer.

Towing a Trailer with a Vehicle without Trailer Provisions (RPO V92)

These vehicles can tow a maximum trailer weight of 2,000 lb. (907 kg).

These vehicles must be modified by installing a new underhood bussed electrical center (UBEC) to provide full functionality for 4 circuits: ground, tail lamps, RH and LH stop/turn lamps. Refer to the Parts Information section in this bulletin for the correct part numbers. To find the original part number, remove the UBEC and look at the side of the UBEC. Perform this modification only if the customers will be using the vehicle to tow.

Due to the omission of information about trailer towing for vehicles without the Trailer Provision (V92) in the Owner's Manual, this modification will only be covered under warranty for the 2007 GMC Acadia, 2007 Saturn OUTLOOK and the 2008 Buick Enclave (built prior to July 2, 2007).

The Owner's Manual for the 2008 GMC Acadia, 2008 Saturn OUTLOOK and 2008 Buick Enclave (built after July 1, 2007) have been corrected and the policy to cover the UBEC replacement as an approved warranty repair for these vehicles has been rescinded. This modification has changed to a customer pay upgrade.

The replacement of the UBEC remains the best solution to upgrade the vehicles wiring for towing. The electrical circuitry for the tail/stop lamps are controlled by the BCM and splicing into the body harness is not recommended.

Towing a Trailer with a Vehicle with Trailer Provisions (RPO V92)

These vehicles can tow a maximum trailer weight of 4,500 lb. (2,041 kg).

It is necessary to modify the backup lamp circuit. Perform this procedure only if the customer will be using the vehicle to tow.

1. Disconnect the X7 connector from the Body Control Module (BCM).
2. Remove the terminal for pin 3 from the BCM X7 connector. The wire to this terminal is dark blue and is the 38 circuit.
3. Re-connect the X7 connector to the BCM.
4. Cut the terminal off the end of this wire and strip the end of the wire.
5. Splice this wire into the 24 circuit wire that goes into BCM connector X6, pin 2. The 24 circuit is light green.

Important: To avoid battery rundown while towing, remove the 50 amp BATT1 fuse in the UBEC. Refer to the dinghy towing procedure in this bulletin.

Recreational Vehicle Towing Information

Important: Vehicles with a 6-speed automatic transmission that are "dinghy towed" must be started at the beginning of each day and at each fuel stop for a minimum of five minutes.

Recreational vehicle towing means towing the vehicle behind another vehicle -- such as behind a motorhome. The two most common types of recreational vehicle towing are known as "dinghy towing" (towing the vehicle with all four wheels on the ground) and "dolly towing" (towing the vehicle with two wheels on the ground and two wheels up on a device known as a "dolly"). With the proper preparation and equipment, many vehicles can be towed in these ways. Refer to the appropriate model/model year Owner Manual for towing preparation guidelines and dolly and dinghy towing procedures. The Towing Chart below summarizes powertrain combination compatibility with dolly and dinghy towing methods.

*Notice: If the vehicle is equipped with a 6T75 six-speed automatic transmission, it can be dinghy towed from the front for unlimited miles at 65 mph (105 km/h). To avoid vehicle damage, never exceed 65 mph (105 km/h) while towing Buick Enclave, GMC Acadia and Saturn OUTLOOK vehicles. The repairs would not be covered by the warranty.

Dinghy Towing Procedure

Notice: If you tow your vehicle without performing each of the steps listed under "Dinghy Towing," you could damage the automatic transmission. Be sure to follow all steps of the dinghy towing procedure prior to and after towing your vehicle.

Notice: Don't tow a vehicle with the front drive wheels on the ground if one of the front tires is a compact spare tire. Towing with two different tire sizes on the front of the vehicle can cause severe damage to the transmission.

Important: Buick Enclave, GMC Acadia and Saturn OUTLOOK vehicles may only be dinghy towed from the front, with all four wheels on the ground.

1. Position the vehicle to tow and then secure it.
2. Shift transmission to PARK (P) and turn the ignition to OFF.
3. Set the parking brake.
4. Turn the ignition to ACCESSORY.
5. Shift your transmission to NEUTRAL (N).
6. To prevent your battery from draining while the vehicle is being towed, remove the 50 amp BATT1 fuse in the UBEC, and store in a safe location.
7. Release the parking brake.

Once you have reached your destination, do the following steps:

1. Set the parking brake.
2. Reinstall the BATT1 fuse.
3. Shift the transmission to PARK (P), turn the ignition key to OFF and remove the key from the ignition.
4. Release the parking brake.

For vehicles repaired under warranty as outlined above, use: