Theory of Operation
The General Temperature Rationality looks at the outputs of the three temperature sensors and compare them
under cold start conditions. Following a start to run delay time, the outputs of the ambient, engine coolant, and
intake air temperature sensors will be compared. If two sensors agree but not the third, the third sensor is declared
as irrational. If all three sensors are irrational the General Temperature Sensor Rationality is failed.
When Monitored:
Ignition on and battery voltage greater than 10 volts.
Set Condition:
Ambient Air, Engine Coolant, and Intake Air Temp sensor inputs are compared under cold start conditions.
After start up the temp readings are monitored. If two of the three readingsagree and the third doesn’t, a DTC
is stored. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes
EXCESSIVE RESISTANCE IN THE SENSOR SIGNAL CIRCUIT
EXCESSIVE RESISTANCE IN THE (K900) SENSOR GROUND CIRCUIT
EXCESSIVE RESISTANCE IN THE (G930) AAT RETURN CIRCUIT
TEMPERATURE SENSOR
PCM
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, read the DTCs.
NOTE: All ECT, Intake Air, and Ambient Air Temperature Sensor codes must bediagnosed and repaired
before continuing.
NOTE: In cold weather, this DTC could be set by a high powered block heater andnorepairwouldbe
required.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.TEMPERATURE SENSOR CIRCUIT
With a scan tool, read the ECT, Ambient Air Temp, and Intake Air Temp Sensor temp values.
Start the engine.
Allow the engine to reach normal operating temperature while monitoring the three Sensor temperature values.
Is the temperature for each of the Sensors increasing properly?
Ye s>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 3
For a complete wiring diagramRefer 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:
The MDS fails to active and take place for cylinder 1. One trip fault.
Possible Causes
(K451) MDS SOLENOID NO.1 CONTROL SHORT TO GROUND
(K451) MDS SOLENOID NO.1 CONTROL OPEN
(Z42) GROUND CIRCUIT OPEN
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID NO.1
PCM
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, read DTCs.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
6.PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal
push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and
Ground circuits.
Were there any problems found?
Ye s>>
Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
7.MDS SOLENOID 1
Turn the ignition off.
Remove the Intake Manifold per Service Information.
Reconnect the Solenoid connector.
Turn the ignition on.
With the scan tool actuate the MDS Solenoid 1.
Can you feel and hear the Solenoid Actuating?
Ye s>>
Go To 8
No>>
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)
8.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?
Ye s>>
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)
No>>
Replace both sets of lifters if no other possible causes remain.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
For a complete wiring diagramRefer 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:
The MDS fails to active and take place for cylinder 4. One trip fault.
Possible Causes
(K452) MDS SOLENOID NO.4 CONTROL SHORT TO GROUND
(K452) MDS SOLENOID NO.4 CONTROL OPEN
(Z42) GROUND CIRCUIT OPEN
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID NO.4
PCM
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, read DTCs.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
7.MDS SOLENOID 4
Turn the ignition off.
Remove the Intake Manifold per Service Information.
Reconnect the Solenoid harness connector.
Turn the ignition on.
With the scan tool actuate the MDS Solenoid 4.
Can you feel and hear the Solenoid Actuating?
Ye s>>
Go To 8
No>>
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 4. If the passages are not clogged with debris,
replace the MDS Solenoid 4.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
8.OIL PASSAGES RESTRICTED
Turn the ignition off.
Remove both Solenoids on Bank 2 of the engine block.
Remove the Bank 2 Cylinder Head per Service Information.
Remove the Lifters from the right engine bank.
Inspect the oil passages to the Solenoids and from the Solenoids to the lifters.
Are the passages blocked?
Ye s>>
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)
No>>
Replace both sets of lifters if no other possible causes remain.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
For a complete wiring diagramRefer 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:
The MDS fails to active and take place for cylinder 6. One trip fault.
Possible Causes
(K453) MDS SOLENOID NO.6 CONTROL SHORT TO GROUND
(K453) MDS SOLENOID NO.6 CONTROL OPEN
(Z42) GROUND CIRCUIT OPEN
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID NO.6
PCM
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, read DTCs.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.MDS SOLENOID NO.6
Turn the ignition off.
Gain access to the MDS Solenoid No.6.
Disconnect the MDS Solenoid No.6 harness connector.
Ignition on, engine not running.
Turn off all accessories.
Using a 12-volt test light connected to the (Z42) Ground circuit, probe
the (K453) MDS Solenoid No.6 Control circuit.
With a scan tool, actuate the MDS Solenoid 6.
Does the 12-volt test light flash on and off?
Ye s>>
Go To 7
No>>
Go To 3
7.MDS SOLENOID 6
Turn the ignition off.
Remove the Intake Manifold per Service Information.
Reconnect the Solenoid connector.
Turn the ignition on.
With the scan tool actuate the MDS Solenoid 6.
Can you feel and hear the Solenoid Actuating?
Ye s>>
Go To 8
No>>
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 6. If the passages are not clogged with debris,
replace the MDS Solenoid 6.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to
9 - ENGINE - STANDARD PROCEDURE)
8.OIL PASSAGES RESTRICTED
Turn the ignition off.
Remove both Solenoids on Bank 2 of the engine block.
Remove the Bank 2 Cylinder Head per Service Information.
Remove the Lifters from the right engine bank.
Inspect the oil passages to the Solenoids and from the Solenoids to the lifters.
Are the passages blocked?
Ye s>>
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)
No>>
Replace both sets of lifters if no other possible causes remain.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
For a complete wiring diagramRefer 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:
The MDS fails to active and take place for cylinder 7. One trip fault.
Possible Causes
(K454) MDS SOLENOID NO.7 CONTROL SHORT TO GROUND
(K454) MDS SOLENOID NO.7 CONTROL OPEN
(Z42) GROUND CIRCUIT OPEN
INSUFFICIENT OIL PRESSURE ACTING ON THE LIFTER LOCKING PINS
OIL PASSAGES RESTRICTED
LIFTER
MDS SOLENOID NO.7
PCM
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, read DTCs.
Is the DTC active at this time?
Ye s>>
Go To 2
No>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
2.MDS SOLENOID NO.7
Turn the ignition off.
Gain access to the MDS Solenoid No.7.
Disconnect the MDS Solenoid No.7 harness connector.
Ignition on, engine not running.
Turn off all accessories.
Using a 12-volt test light connected to the (Z904) Ground circuit, probe
the (K454) MDS Solenoid No.7 Control circuit.
With a scan tool, actuate the MDS Solenoid 7.
Does the 12-volt test light flash on and off?
Ye s>>
Go To 7
No>>
Go To 3