Illuminated Service AWD Lamp with PTU DTCs Set

Some 2017-2021 Acadia, XT5; 2018-2021 Enclave, Traverse; 2019-2021 Blazer; and 2020-2021 XT6 models equipped with the 2.0L engine (RPO LSY, LTG), 2.5L engine (RPO LCV) or 3.6L engine (RPO LFY, LGX) and All-Wheel Drive (RPO F48) may have an illuminated Service AWD lamp on the instrument cluster and several Power Transfer Unit DTCs set (C1260—C1267, C1290—C1293, C1295 and C1296). These conditions may be the result of debris in the Power Transfer Unit (PTU) extension housing obstructing the shift mechanism that the actuator motor cannot overcome.

The PTU extension housing, which shares a fluid system with the transmission, is separate from the PTU gear assembly. The shift mechanism resides in the extension housing.

 

PTU Operation

The primary function of the PTU (Fig. 9) is to receive power from the transmission and transfer it through the propeller shaft to the rear differential using helical and hypoid gear sets. The disconnect-design PTU has the ability to internally engage and send power and torque to the rear propeller shaft, activating AWD mode. Shifting is performed by a PTU-mounted actuator motor, internal linear and rotary cams, and shift collar. The actuator motor operates as directed by the rear differential clutch control module to perform the shifting operations.

 

Fig. 9

 

Check DTCs

Follow the appropriate Service Information for any DTCs set. If diagnosis leads to a PTU condition, remove the PTU from the vehicle and, while on the bench, complete an inspection of parts and clean the extension housing. Clean and inspect the extension housing only, not the PTU assembly.

TIP: Unless diagnosis points to failure of the PTU or actuator motor, do not replace these components. Some parts returned to the Warranty Parts Center have been tested with no trouble found.

After cleaning and inspection, reinstall the PTU in the vehicle, test drive and top off transmission fluid.

 

Extension Housing Cleaning Procedure

Follow the cleaning procedure for the PTU extension housing described in Bulletin #22-NA-006. Here are a few of the highlights of the procedure.

To remove the PTU (Fig. 10, #1) from the vehicle, refer to Power Transfer Unit Case Replacement in the appropriate Service Information.

 

Fig. 10

 

When removing the extension housing to PTU case bolts, check if the bolts have an inverted torx head. Replace the inverted torx head bolts with new hex head attachment bolts. (Fig. 11, #1)

 

Fig. 11

 

Also remove and discard the extension housing seal, half shaft O-ring seal and retainer. (Fig. 12)

 

Fig. 12

 

Remove the power transfer disconnect rotary cam and the power transfer disconnect linear cam from the extension housing by shaking the assembly to get the cams to slide down the IDS. Inspect the power transfer disconnect linear cam for signs of abrasion, scratches etc. Replace the cam if there is any damage. Also inspect the extension housing for internal damage. (Fig. 13)

 

Fig. 13

 

Clean all extension housing parts thoroughly. (Fig. 14) Be sure to pay close attention to the rotary cam bore, the worm gear bore, and the bearing at the bottom of the worm gear bore. Dry components using compressed air to remove any remaining solvent.

 

Fig. 14

 

In addition, inspect the power transfer disconnect rotary cam for damage to the teeth. (Fig. 15) Replace the rotary cam if any damage is found, such as broken teeth. Check the clutch kit (shift collar) for damage as well. Only replace if damage is found.

 

Fig. 15

 

During reassembly of the extension housing on the PTU housing, minor rotations may be needed to slide the extension assembly into the PTU housing. (Fig. 16) Also, inspect the PTU shift actuator and rotate the worm gear to line up with the shift actuator drive.

 

Fig. 16

 

For the complete inspection and cleaning procedures, as well as part information, refer to Bulletin #22-NA-006.

 

– Thanks to Robert Cross and Tom Burlingame