Information for Diagnosis and Repair of Rear Air Suspension (RPO G67)

The purpose of this bulletin is to provide information for diagnosis and repair of the rear air suspension (RPO G67).

Customer comments on the rear suspension sagging or the vehicle sitting low in the rear (i.e., the vehicle has a nose-up attitude when parked) may be caused by the air compressor’s 8-way electrical connector, which may not be fully locked into position. This may potentially cause an intermittent operating condition.

For this condition, perform the following steps PRIOR to attempting to replace the compressor:

1. Perform appropriate SI diagnostics. Refer to Diagnostic Starting Point - Air Suspension, Symptoms - Air Suspension and/or any relevant DTC diagnostics in SI.
2. Perform a tug test on the connector while wiggling it to determine if it is fully seated. Even if the lock tab is not in the proper position, the seal will hold the connector in the cavity, but the connector may not be making proper contact.
3. Ensure the battery is fully charged. If the battery voltage drops to 12.6 V or lower, the compressor will not operate properly. Refer to Battery Charging in SI for information on charging battery, if necessary.

Customer comments on the vehicle leaning side-to-side (i.e., one side of the vehicle is higher than the other) may be caused by out-of-adjustment rear air suspension sensors.

For this condition, perform the following steps:

1. Perform an air spring sensor calibration. Refer to Air Spring Sensor Calibration in SI.
2. When adjusting the rear air suspension, install new anti-rotation bolts, P/N 11569736, in the right hand bolt location on the sensor and tighten this bolt first to the appropriate SI torque specification.
3. Recheck the D-height after cycling the suspension. Follow the appropriate SI diagnostics if the lean condition re-occurs.

1. When inspecting the trim height (refer to Trim Height Inspection in SI), the vehicle D-height should be allowed to stabilize with the ignition key in the "ON" position for a few minutes before proceeding. Once the vehicle D-height is stabilized the ignition key should be turned "OFF" prior to the suspension jounce procedure, and "D" height measurement. Jouncing the suspension with the ignition key "RUN" can induce a condition which can cause an inoperative compressor for a period of time, which could be interpreted as a failed compressor. To reset this condition, cycle the ignition between RUN and OFF.
2. The rear trim height specifications apply to the D-height, or the vertical distance between the top surface of the axle and the center-line of the hole in the jounce bumper reinforcement bracket on the frame. The trim height specifications DO NOT apply to the wheelhouse panel heights.
3. Do not use coil spring equipped vehicles as a visual and/or D-height reference for comparison with vehicles equipped with rear air suspension. At curb weight, the coil spring vehicles will set higher in the rear.
4. Use of the accessory inflator (refer to Accessory Inflator in the appropriate Owner's Manual) with the ignition key turned to the "ON" position can result in a temporarily inoperative condition if the air suspension attempts to raise the rear of the vehicle. If this occurs, a RUN/OFF key cycle is necessary to reset the compressor. To avoid these conditions, only use the auxiliary inflator when the ignition key is OFF. In addition, when the auxiliary inflator is in use, it will time out after 5 minutes and must be allowed to cool off before continued operation can begin again.
5. When removing air suspension lines, or performing air suspension air leak diagnosis, the compressor air line fittings should not be re-tightened before the air springs have fully exhausted, as a pinched O-ring may result. Also, if the fittings are fully removed, the O-rings should be checked for cuts/cracks before reinstallation into the compressor to prevent leaks.
6. Air Suspension Description and Operation in SI may lead to unnecessary compressor replacements for suspension sagging comments. Vehicle testing has shown that the D-height may appear to drop more than 25 mm (1.0 in) with a 25°C (45[ordm ]F) temperature drop as stated, because it will be difficult to measure and account for normally heated vehicle components (such as the exhaust system) that will affect the temperature and height drop. The only way to accurately check for a leaking suspension is to inspect the air lines for leaks, using soapy water. It may not be feasible to use the check described in the Air Suspension Description and Operation, depending on the thermal stability of the service center environment. The specification is a 1.4 mm (0.055 in) drop in 24 hrs in a controlled temperature environment, after the vehicle temperature has stabilized. This will be very difficult to accomplish and even a temperature change of as little as 2.8°C (5[ordm ]F) can change the suspension height by more than 1.4 mm (0.055 in). Keep in mind the suspension will drop for temperature decreases and will actually increase for higher temperatures.