C0285 relates to a pressure fault, or incorrect indication of one, from a component called the medium pressue accumulator switch. It is attached to the brake pressure modulator valve. There is a service bulletin on this that came out in 2004, here is a copy of it.
#04-05-25-008: ABS Light On, Service Stability System Message Displayed, Stability System Disabled Indicator On, DTCs C0285 and C0286 (Install New Medium Pressure Accumulator Switch) - (Aug 6, 2004)
Subject: ABS Light On, Service Stability System Message Displayed, Stability System Disabled Indicator On, DTCs C0285 and C0286 (Install New Medium Pressure Accumulator Switch)
Models: 2002 Cadillac Escalade, Escalade EXT
with Vehicle Stability Enhancement System (VSES) (RPO JL4)
Some customers may comment on the Antilock Brake System (ABS) light coming on. Others may comment on the Service Stability Message Displayed and/or the Stability System Disabled Indicator being on. Technicians may find Diagnostic Trouble Codes (DTCs) C0285 and/or C0286.
Technicians are to install a new medium pressure accumulator (MPA) switch. The new switch, P/N 88983914, is grey in color. The previous switch, P/N 12545898, is black in color and will not fix this concern.
Switch Assembly, Brake Pressure Differential
If it has the above mentioned black switch, I would correct the situation by replacing it. If the code returns, you will most likely need the brake pressure modulator valve. Here is an illustration of the unit, it doesn't show it located in it's natural environment. The BPMV is mounted to the inside of the left frame rail, forward of he fuel tank. The switch in question is the one diagonal from the reference #1.
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Sunday, October 3rd, 2010 AT 11:17 PM