Diagnosis

Rear Strut Knock:

^ If rear strut knock exists activate the rear suspension using the procedure in Technical Bulletin section 66, number 7. If the system activates correctly, roadtest the vehicle. If knocking is eliminated, perform a second roadtest after 24 hours.

^ If no rear strut knocking exists, the system is operating normally.

^ If knocking persists or reoccurs, replace the Down Solenoid Valve and the Up Leveling Non-Return Valve.
^ If the ride leveling system does not activate, perform a power hydraulic pressure test using the procedure in Technical Bulletin section 66, number 5. If necessary, perform a JDS test.

^ If no up leveling occurs and during the hydraulic pressure test (Technical Bulletin section 66, number 5, test 7) the rear suspension pressure rises to only 28 BAR, replace the Down Solenoid Valve.

^ If no up leveling occurs and JDS fails the solenoid valve block assembly, raise the ride level sensor link rod. With the engine running at 1000 rpm, check for the hydraulic pressure relief valve cycling (pump to valve block hose alternating between flexed and relaxed condition). If the pressure relief valve cycles and the rear suspension does not rise, replace the Up Solenoid Valve. If the pressure relief valve does not cycle, replace the Charge Solenoid Valve.

^ If there is no down leveling and JDS fails the solenoid valve block assembly, replace the Down Solenoid Valve.


Rear Suspension Groan:

If an extended "groan" noise is emitted from the solenoid valve block during down leveling, replace the Down Solenoid Valve.


Brake System Grunt (1988 and 1989 M.Y. only):

If a brief "grunt" noise is emitted from the solenoid valve block after repeated brake applications, replace the Charge (Load) Solenoid Valve.


"Low Brake Pressure" Warnings (1988 and 1989 M.Y. only):

^ If the VCM displays a "Low Brake Pressure" warning and JDS fails the solenoid valve block assembly, replace the Charge (Load) Solenoid Valve.

^ If a power hydraulic pressure test (Technical Bulletin section 66, number 5) indicates a low pressure condition (test 1) and a correctly operating hydraulic pump (Test 2), and no electrical fault exists, replace the Charge (Load) Solenoid Valve.