Displacement on Demand (DoD) System Diagnosis. Isuzu Ascender

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2006 🢒 Ascender - 2WD 🢒 Engine 🢒 Engine Controls - 5.3L 🢒 Displacement on Demand (DoD) System Diagnosis

Circuit Description

To provide maximum fuel economy under light load driving conditions, the engine control module (ECM) will command the displacement on demand (DoD) system ON to deactivate engine cylinders 1 and 7 on the left bank, and cylinders 4 and 6 on the right bank, switching to a V4 mode. The DoD systems use an electro-hydraulic actuator device called the valve lifter oil manifold (VLOM) assembly. The VLOM consists of 4 electrically operated normally closed solenoids that directs engine oil pressure to the deactivating DoD valve lifters. All 4 VLOM solenoids are connected in parallel to a fused ignition 1 voltage circuit supplied by the powertrain relay. The ground or control circuit for each solenoid is connected to an individual low side driver internal to the ECM. When all enabling conditions for V4 mode are met, the ECM will command the low side driver to turn ON, grounding each VLOM solenoid control circuit, in engine firing order sequence.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

A functional service bay test is performed to determine if the cylinders can deactivate. The vacuum gage will display a steady regular fluctuating drop of engine vacuum on a cylinder that has both valves deactivated. This test must be performed with a vacuum gage only and not a combination pressure and vacuum gage. The gage on a hand held vacuum pump or Mityvac will work fine for this test.

Perform a road test while monitoring the cylinder deactivation data parameters with a scan tool. If the engine does not switch to a V4 mode, then review the inhibit reasons listed in the DoD system description.

Step	Action	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Turn OFF the ignition. Disconnect the evaporative emission (EVAP) solenoid vacuum tube at the intake manifold. Connect a vacuum gage to the EVAP vacuum tube fitting on the intake manifold. Connect a scan tool to the diagnostic link connector (DLC). Start the engine. Allow the engine to reach operating temperature. Command each displacement on demand (DoD) solenoid ON, one at a time, using the Output Control function of the scan tool. Does the engine run rough, and does the needle on the vacuum gage have a steady fluctuating drop of 0.5-2 inches Hg or vacuum when each DoD solenoid is commanded ON?	Go to Step 3	Go to Displacement on Demand (DoD) System Diagnosis in Engine Mechanical
3	Clear the DTCs with a scan tool. Monitor the Cylinder Deactivation System Command parameter, and the Deactivation Solenoid Command parameter for cylinders #1, 4, 6, and 7 with a scan tool in the Cylinder Deactivation Data menu. Road test the vehicle under light throttle and load conditions that will allow the engine control module (ECM) to command V4 mode. Does the scan tool display V4 mode for the Cylinder Deactivation System Command parameter, and ON for each Cylinder Deactivation Solenoid Command parameter?	Go to Step 4	Go to Displacement on Demand (DoD) System Description
4	Review the DoD driving information in the Features and Controls section of the owners manual with the vehicle operator, or instruct the vehicle operator in the proper driving techniques to obtain V4 mode. Did you complete the review of the owners manual information or proper driving techniques to obtain V4 mode with the vehicle operator?	Go to Step 5	--
5	Clear the DTCs with a scan tool. Start the engine. Operate the vehicle for 5 minutes. Does a DTC set during this ignition cycle?	Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information	System OK