Pinpoint Test F: Spongy/Soft/Low Brake Pedal With No Warning Indicator

Anti-Lock Control

Pinpoint Tests

Pinpoint Test F: Spongy/Soft/Low Brake Pedal with No Warning Indicator

Normal Operation

The brake pedal should be firm when applied.

This pinpoint test is intended to diagnose the following:
- Base brake system
- Hydraulic Control Unit (HCU)



PINPOINT TEST F: SPONGY/SOFT/LOW BRAKE PEDAL WITH NO WARNING INDICATOR

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F1 CHECK THE BASE BRAKE COMPONENTS


- Visually inspect the brake hoses and tubes from the HCU to the brake calipers.
- Visually inspect the calipers and brake components.
- Are any of these components damaged or leaking?

Yes
REPAIR or INSTALL new components as necessary. TEST the system for normal operation.

No
GO to F2.

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F2 CHECK FOR A LEAKING DUMP VALVE


- Ignition OFF.
- Remove the rubber boots from the 2 HCU low pressure accumulators and insert a clean steel implement (such as a paper clip or a small screwdriver) into each low pressure accumulator.




- Ignition ON.
- NOTE: A leaking dump valve is similar to the master cylinder bypass condition. It is important that the pedal be quickly and forcefully applied to rule out master cylinder bypass as a condition.
- Have an assistant press hard on the brake pedal while observing the steel implements.
- Do either of the implements move out 6.35 mm (0.25 in) or more?

Yes
INSTALL a new HCU. REFER to Hydraulic Control Unit (HCU) Removal and Replacement.

No
REMOVE the steel implements. INSTALL the rubber boots on each low pressure accumulator.

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