| Subject: | Supplement to Bulletin (08-05-22-001) |
| Models: | 2008 -2009 Chevrolet HHR SS |
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Some customers may complain that they "still" do not like the normal operational characteristics of the OHB brake system AFTER the EBCM has been reprogrammed. This reprogram does enhance the feel of the OHB system significantly.
Recommendation/Instructions:
As described in TSB 08-05-22-001 the following Optimized Hydraulic Brake (OHB) characteristics are considered to be normal and no mechanical parts should be replaced in an effort to change the operation of the system:
| • | Ratchet sound coming from the brake system during OHB activation. |
| • | Brake pedal movement or pulsation when the OHB is active. |
| • | Increased brake pedal effort under low brake booster vacuum. |
| • | Change in brake pedal effort when OHB is active. |
| • | Frequent brake stops may result in OHB activation. |
| • | High altitude driving may result in OHB activation. |
Refer to Corporate Bulletin Number 07-05-22-002 for further information on Optimized Hydraulic Boost Brake System Characteristics.
DO NOT replace the brake vacuum booster, brake vacuum sensor, EBCM or ABS module for this condition.
GM Engineering is working on developing an additional service repair for vehicles that the customers feel do not provide adequate brake assist after the calibration has been performed per TSB 08-05-22-001. This repair procedure is not yet available and
no other repairs should be attempted. Further information will be provided when any additional repair is available.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
