Just some additional information to close out this subject and clean my desk off:
The subject vehicle count was 12,999 (5,876 Solstice GXPs and 7,123 Sky Redlines).
GM had received 212 unique (VINs) reports which included 12 that matched up with NHTSA reports.
350 of the subject vehicles had had "warranty" work done for this issue (150 Solstice GXPs and 200 Sky Redlines). This mainly involved the EBC reprogramming bulletin from early last Winter.
The 2008 MY Pontiac Solstice GXP and Saturn Sky Redline vehicles equipped with 2.0L turbocharged engine include the Optimized Hydraulic Brake (OHB) supplemental hydraulic assist system.
The OHB system may be active for up to 90 seconds after vehicle startup, during preheating of the catalytic converter, which improves vehicle emissions performance during cold starts. Catalytic heating involves retarding spark and opening the throttle to maintain idle, which has the effect of depleating engine vacuum.
The OHB function is active during conditions of low brake booster vacuum. This can occur after the vehicle has been sitting for at least 4 hours. To maintain brake power assist (which is supplied by engine vacuum when the vehicle is warm), the subject vehicles employ OHB supplemental hydraulic assist during catalytic heating. This supplemental assist is acheived by increasing brake pressure through the electronic stability control pump.
In May 2008, NHTS personnel drove both teh subject and peer vehicles to compare the brake system performance characteristics by performing low speed parking lot maneuvers during cold start conditions. GM demonstrated that the driver may feel some pedal feedback (pulsation) and some non-linear brake gain; i.e., higher pedal effort to acheive a given deceleration during initial vehilce warm-up. While these small differences in performance displease some customers, GMM's evaluation is that they do not degrade the performance of the brake system.
GM has made continuous improvements to the OHB operation and provide educational informaiton anout OHB system to customers and dealers.
In June 2007, GM included a despcription of the OHB operation in the owner's manual and released an informational service bulletin to dealers that described OHB system operation.
In October 2007, GM included a glove box hang tag that described the OHB operation and characteristics.
Fom July through October 2007, GM reviewed customer reports regarding concerns of the OHB operation and the brake pedal feel. In November 2007, GM released an OHB service calibration. This improved the brake pedal feel.
Of the 228 (212 unique VINs) complaints received by GM regarding the alleged cndition, 218 complaints were received prior to releasing the OHB service calibration. After the service calibration was released GM received 10 reports. At the same time, GM continued to seek additional system refinements to improve the customer acceptance.
In April 2008 GM released an ECM calibration service bulletin which made brake pedal effort and travel, in a cold start vehicle, closer to that of a warmed-up vehicle.
GM found 207 GM reports for subject vehicles with automatic transmission. GM also found 5 reports for subject vehilces wiht manual transmission.
The reasons for this difference are:
A) First, drivers of manual transmission vehicles typically increase engine speed (depress the accelerator pedal) momentarily whice releasing the clutch pedal to move the vehicle. Release of the accelrator pedal after the increase in engine rpm elevates the vacuum in the brake booster. Since automatic transmissions do not require the same apply and release motion of the accelerator pedal, there is no additional vacuum stored in the booster during and idle drive condition.
B) Second, during most low speed braking maneuvers, the clutch is depressed. This disengages the drive torque from the wheels, which in turn reduces the amount of brake line pressure needed to stop the vehicle. On automatic transmission vehicle, the drive torque is being applied to the wheels as long as the vehicle is in gear, this additional drive torque needs to be overcome by the brake system.
Based on the month of vehicle sold, GM saw a decline in the rate of reports associated with the OHB system from October through Janaury 2008. Since the OHB service cal was not released for vehicle produciton, this change amy be attributed to greater customer awareness of the OHB functionality (possibly due to the addition of the glove box hang tag).
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INFORMATION POSTED ON SITE
Any GM Solstice Service Manual and Service Bulletin information found here on site, or Sales and Product information should be thought of as correct and accurate as of the date posted. After that any information or procedure should be confirmed as still correct with your dealership.
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