Low Brake Pressure - Diagnosing Warning On the VCM

91jaguar01

SECTION: 66

No: 14


LOW BRAKE PRESSURE

WARNING ON THE VCM


Model: 88 - 89 My SEDAN RANGE Date: JANUARY, 1991

KEY POINTS: ACCUMULATOR TEST PROCEDURE


ISSUE:

When investigating a VCM warning for "Low Brake Pressure" the following test procedure must be performed first to determine the performance of the accumulator.

CHECKING PROCEDURE:

^ Start the engine and run at 1000 RPM for 25 seconds.

^ Switch off the engine, and then switch the key back to the ON position (Position II).

^ Press the brake pedal firmly and then release. Repeat the brake application once every 3 seconds while observing the VCM display.

^ Count and record the number of brake applications made before a "Brake Failure" or "Low Brake Pressure" warning is indicated on the VCM.


NOTE: An "Anti-Lock Failure" warning will be given throughout the test. This is normal when the engine is not running.


If 5 or More Brake Applications are Required:

The accumulator gas charge is good. Take no further action.

If 4 or Less Brake Applications are Required:

Perform a Power Hydraulic Accumulator Pre-Charge Test (refer to Technical Bulletin section 66, number 5, Test 1). If the "flick-up" pressure is below 18 BAR, replace the accumulator vessel and re-check the number of brake applications (as detailed above).