Auto-Leveling Rear Suspension Inoperative – 2015 Chevrolet & GMC

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Subject:	Auto-Leveling Rear Suspension Inoperative
Models:	2015 Chevrolet Suburban, Tahoe
	2015 GMC Yukon, Yukon XL
	2WD Vehicles Equipped with Auto Leveling Rear Suspension
	(RPO Z85 and AVF)

Service procedure for 2015 model year Chevrolet Tahoe and Chevrolet Suburban, GMC Yukon and GMC Yukon XL 2WD vehicles equipped with auto levelling rear suspension (RPO Z85 and AVF).

These vehicles may have an auto-leveling feature that is inoperative. The auto-leveling feature works by sensing when the rear of the vehicle is loaded.

Rear shock absorbers’ integral air sacks (boots) are inflated to compensate and level the vehicle. Customers may notice the rear trim height lower in the rear of the vehicle when loaded comparable to vehicles without auto-leveling rear suspension.

Parts Information

Service Procedure

This procedure involves:

• Inspection of the rear auto leveling air shocks
• Reprogramming the Engine Control Module (ECM)
• Verification of the level control system function
• Replacement of both shocks in pairs, if necessary

Rear Shock Absorber Inspection

1. Inspect the shocks while the vehicle is on the ground, or on a drive-on hoist, with the shocks loaded. Look for the air sacks being kinked, pinched, or trapped.

Air Sack Damage

Arrows point to trapped air sack between the shock body and the dirt shield. If this condition exists, the shock must be replaced. Inspect for rolling, folding, or any kinks in the rubber tube. Any shock with these conditions must be replaced.

• Raise and support the vehicle, with the rear axle unsupported to allow the rear shocks to extend.
• Inspect the lower roll of the air sack. Some “polishing” of the rubber (as seen in the picture below) is normal and ok.
  If the sack exhibits any cracking, splitting, peeling, is darker than the surrounding rubber, or shows any spalling or material loss, it is damaged and must be replaced.

Air Sack Damage

Engine Control Module (ECM) Reprogramming

Reprogram the ECM with the latest calibration. Refer to K20 Engine Control Module: Programming and Setup.

System Pressure Check

To complete an Air Replenishment Cycle (ARC), the vehicle must have the engine running. For further information refer to Automatic Level Control Description and Operation (With Z85).

1. Start the engine and listen for the ARC running the system air compressor for 3 seconds. Note ride height of vehicle adjusting.
2. Ignition OFF.
3. Raise and support the vehicle with the rear axle unsupported to allow the rear shocks to extend.

1. • Check System Pressure Check shock absorbers for system pressure. Shock “A” has no pressure, and displays a tapered “waist” just above the bottom roll of the boot. Shock “B” has the correct pressure with a nearly uniform width top to bottom.

1. • Air Sack Pressure Check Squeeze the air sack. The more firm the sack, the more pressure is present. If, after pressurizing the system the air sack is not holding pressure, it is damaged and must be replaced.

Rear Shock Absorber Replacement

For rear shock absorber replacement refer to Rear Leveling Shock Absorber

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