Here is that bulletin for the bpmv, but often it is just a brake switch so i really don't want to push you towards a bpmv without really being able to monitor that brake switch first.Service Information 2008 Chevrolet Impala | Impala VIN W Service Manual | Document ID:(###) ###-####PIC5695: Cruise Control Inoperative And No DTCs Cruise Disengage History Brake Or Pedal Initialize - (Jun 19, 2012)Subject:Cruise Control Inoperative And No DTCs Cruise Disengage History Brake Or Pedal Initialize Models:2008 - 2012 Buick Lucerne ENGINE
RPO's [LD8, L37, LZ9, LGD]2007 - 2011 Cadillac DTS all engines2008 - 2011 Chevrolet Impala all enginesWith StabiliTrak (RPO JL4)The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.Condition/Concern:Some customers may comment that cruise control will not engage or will not stay engaged and there are no DTCs and scan tool cruise disengage history is "Brake". This condition may occur due to a faulty brake pressure sensor, located in Brake Pressure Modulator Valve (BPMV).Recommendation/Instructions:To correct this condition complete the following steps:Verify that scan tool cruise disengage history parameter reads "Brake". Diagnose any other scan tool cruise disengage history first using eSI diagnostics.Note: Scan tool cruise disengage history parameter will read "Brake" based on either of the following two inputs:A. BCM detecting a brake pedal apply using brake pedal position (BPP) sensor.B. EBCM detecting a brake applies using the brake pressure sensor within BPMV.Verify that DTC P0703, P0572, and P0573 is not set.Note: If any of the DTCs are set, refer to eSI for the proper DTC diagnostics.With the brake pedal fully released, verify the EBCM indicates brake released. Tech 2 Chassis => EBCM => Data Display => VSES => BPP Signal parameter = "Released".While BPP Signal parameter still reads "Released", verify the Brake Pressure Sensor Input scan tool parameter value is equal to or less than 0.5V.If greater than specified value with no other scan tool cruise control disengage history, and the cruise control inoperative, replace BPMV.Proceed with eSI diagnostics, if cruise control inoperative condition persists after completing these steps.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.GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION© 2016 General Motors. All rights reserved.