P3400-MDS RATIONALITY BANK 1

For a complete wiring diagram Refer to Section 8W.

Theory of Operation

When all criteria has been met, power is supplied to each MDS Solenoid when the engine is making a transition from 8 cylinder mode to 4 cylinder mode. By actuating the solenoid, oil pressure is raised to the pair of lifters that coincide with each particular solenoid. The oil pressure pushes in the locking pins that allows the lifter to collapse, decoupling the valves and camshaft.

When Monitored:
Transition from 8 to 4 cylinder mode.
Set Condition:
O2 sensor readings on Bank 1 side indicate a lean condition while in 4 cylinder mode. One trip fault.

Possible Causes

INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS

OIL PASSAGES RESTRICTED

LIFTER

MDS SOLENOID

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1. ACTIVE DTC

Ignition on, engine not running.
With a scan tool, select View DTCs.

NOTE: Diagnose any Oil Pressure DTCs before continuing.

Is the DTC Active at this time?

Yes

Go To 2

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2. MDS SOLENOID 1

Turn the ignition off.
Remove the Intake Manifold per Service Information.
Turn the ignition on.
With the scan tool actuate the MDS Solenoid 1.

Can you feel and hear the Solenoid Actuating?

Yes

Go To 3

Remove the Solenoid and check for any debris that may be blocking the oil passages to the Solenoid. If the passages are clogged, clean the passages and replace the MDS Solenoid 1. If the passages are not clogged with debris, replace the MDS Solenoid 1.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

3. MDS SOLENOID 7

With the scan tool actuate the MDS Solenoid 7.

Can you feel and hear the Solenoid Actuating?

Yes

Go To 4

Remove the Solenoid and check for any debris that may be blocking the oil passages to the Solenoid. If the passages are restricted, clean the passages and replace the MDS Solenoid 7. If the passages are not clogged with debris, replace the MDS Solenoid 7.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

4. OIL PASSAGES RESTRICTED

Turn the ignition off.
Remove both Solenoids on Bank 1 of the engine block.
Remove the Bank 1 Cylinder Head per Service Information.
Remove the Lifters from the left engine bank.
Inspect the oil passages to the Solenoids and from the Solenoids to the lifters.

Are the passages blocked?

Yes

Clean the oil passages as necessary. If the entire engine is restricted disassembly of the entire engine block may be necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace both sets of lifters if no other possible causes remain.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)