The Cylinder Deactivation (Active Fuel Management) System Compression Test is
a functional test of the Valve Lifter Oil Manifold (VLOM) and valve lifters.
Using a compression gauge, the technician can monitor the specific cylinders ability
to go into and out of cylinder deactivation as commanded by the scan tool. The actual
pressure values on the compression gauge are not as critical as is observing the on-off
switching action of the solenoid and valve lifters.
- Inspect the engine oil level. Fill, as required.
- Perform the Diagnostic System Check - Vehicle. Refer to
Diagnostic System Check - Vehicle.
- Disable the ignition system for the cylinder to be tested, by disconnecting
the electrical wire harness to the ignition coil.
- Disable the fuel injection system for the cylinder to be tested, by disconnecting
the electrical wire harness to the fuel injector.
- Remove the spark plug and wire for the cylinder to be tested.
- Install a 0-1 378 kPa (0-200 psi) compression
gauge.
- Start the engine.
- Using the scan tool output controls, command the solenoid ON, for the
cylinder to be deactivated.
- Depress the Schrader valve on the compression gauge, in order to release
the pressure and zero the gauge. With the engine running and the cylinder in cylinder
deactivation mode, the compression reading should be less than 172 kPa (25 psi).
- Using the scan tool, de-energize the solenoid while observing the
reading on the compression gauge. With the engine running and the cylinder NOT in
cylinder deactivation mode, the compression gauge reading should increase quickly
to greater than 345 kPa (50 psi).
Important: Only 1 cylinder can be tested at a
time. When testing has been completed on a specific cylinder, the wire harness electrical
connectors, spark plug, and spark plug wire must be installed prior to testing of
each additional cylinder.
- Test each of the 4 cylinder deactivation cylinders, 1 at a time.
If the readings are not within specifications, remove, and test the VLOM, as required.
Refer to
Valve Lifter Oil Manifold Replacement and
Cylinder Deactivation (Active Fuel Management) Valve Lifter Oil Manifold Diagnosis and Testing.
- If the compression test has been performed and all cylinder deactivation
cylinders are operating within specifications, the cylinder deactivation system is
performing as designed and no repairs are required.
- Clear the DTCs with a scan tool.