On two occasions last summer my wife had the ABS engage in non emergency braking situations. She was stopping normally and the brake pedal became very hard to engage (hard to press) and she states that with extreme pressure the ABS engaged and she was able to stop. No warning lights activated on the dash. Both occasions the temp was very high with high humidity. Figure 90+ temp which is on the extreme high side for us in Maine. The problem has NOT reoccurred, but as summer and high heat approach I am trying to narrow the issue in the event that it is related to high heat/humidity situations. Before I buy and have installed a new Master Cylinder Assembly has anyone encountered a similar problem and an alternate remedy? I have not had a thorough inspection done on the brakes themselves which would probably be a good first step. Without a warning light would there be any error codes to check?