C066E: Service/Park Brake Chamber Pressure Too High

What it means

The module monitors pressure in the service/park brake chamber. It sets this code when the reported pressure exceeds the upper limit used by the system.

At a glance

• Usually lights the ABS or stability-control warning light
• The engine or gearbox may go into limp mode

How it works

The brake control system monitors pressure in the service/park brake chamber on equipped air-brake vehicles. C066E sets when the reported chamber pressure is above the system's upper limit; a stuck pressure regulator is one possible cause.

Common causes

Most likely first.

1. Pressure regulator stuck

Symptoms

• ABS warning light on
• ESC/stability control deactivated
• Possible reduced brake assist
• Speedometer may behave erratically

How to diagnose it

1. Check the brake-system warnings and live chamber pressure data, if available, to confirm whether the high reading is current or intermittent.
2. Inspect the service/park chamber pressure sensor connector and wiring for damage or a short that could cause an incorrect reading.
3. Check air-system pressure indications and compare chamber pressure readings using the manufacturer's procedure.
4. Inspect the pressure regulator and related air lines for a regulator that is stuck or not controlling pressure correctly.
5. Test the pressure sensor and regulator against the manufacturer's specification before replacing either part.

Common fixes

• Repair damaged wiring or a poor connection at the chamber pressure sensor.
• Replace or repair a pressure regulator confirmed to be stuck.
• Correct a faulty sensor or connection if testing shows the high reading is inaccurate.

Can I keep driving?

Do not continue driving if brake warnings appear, air pressure is outside the vehicle's operating range, or braking or parking-brake operation is abnormal. High chamber pressure can indicate a brake-system control problem; arrange inspection before relying on the vehicle.