G8 V6-3.6L (2008)
The completed worksheet at the end of this bulletin must be attached to the hard copy of the repair order.
1. Measure radial force variation and radial runout.
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If a road force/balancing machine is used, record radial force variation (RFV) on the worksheet at the end of this bulletin. If one or more of the
tire/wheel assemblies read more than 18 lbs (8 kg), match mount the tire to the wheel to get below 18 lbs (8 kg). Readings of 12 lbs (5 kg) or
less are preferable for sensitive customers. If the machine is not available and the EVA data suggests there is an issue, swap the tire and wheel
assemblies from the front to the back. Re-check on the EVA and if the problem still exists, test another vehicle to find tires that do not exhibit
the same frequency and swap those tires onto the subject vehicle.
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If a runout/balancing machine is used, record radial runout of the tire/wheel assemblies on the worksheet at the end of this bulletin. If one or
more of the tire/wheel assemblies are more than.040 in (0.10 cm), match mount the tire to the wheel to get below.040 in (0.10 cm). Readings
of.030 in (0.08 cm) or less are preferable for sensitive customers.
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If the RFV or runout cannot be reduced to an acceptable level, replace the affected tire(s) under the guidelines of the GM Tire Warranty.
2. Place tires with lowest RFV on the front of the vehicle.
3. Road test the vehicle to determine if the shake/vibration has been eliminated.
Brake Rotor Runout
If the brake pedal does not pulsate objectionably, but the corrections above did not alleviate the condition, measure the radial runout of the brake rotors
to see if one (or more) have elevated runout measurements. If the lateral run out (LRO) measurement is 0.050 mm (0.002 in) or LESS, no correction is
necessary. If this measurement is greater, refer to Corporate Bulletin Number 00-05-22-002L: Disc Brake Warranty Service and Procedures for
additional information on correcting rotor runout conditions.
Active Fuel Management (AFM) - G8 GT Only (6.0L V8)
Important
Active Fuel Management is only present on G8 GT models.
The engine in the G8 GT is an 8-cylinder unit that is capable of deactivating 4-cylinders to conserve fuel during periods of reduced power requirement.
Some customers may be sensitive to the change in engine frequency (both in feel and exhaust tone) when Active Fuel Management is engaged. In order
to minimize this sensation, 2009 Pontiac G8 GT models built with VIN 9L3 (2009.5 M Y) have revised engine mounts that reduce the transmitted
vibration from the engine. Vehicles equipped with these revised mounts should not be a concern.
During a road test (with or without the customer), this concern may be isolated by disabling Active Fuel Management. If the customer is available, it may
be of value to let the customer drive the vehicle. In order to disable this feature, you will engage 6th gear manually by performing the following steps:
1. Shift the transmission to "D" (1).
2. Accelerate on a suitable road to a sustainable 55-70 mph (88-112 km/h).
3. Adjust your speed until the objectionable vibration is felt.
4. Move the shifter to the manual shift gate (2). This will engage the "sport shift" mode and automatically initiate a downshift to 5th gear if the
vehicle is in top gear.
5. Move the shift lever forward to engage manual transmission control (3). The vehicle DIC will display "Active Select On".