P1523

P1523-VCM HIGH PRESSURE OIL ABSENT

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

MultiAir is an electronically controlled variable intake valve phase and lift system. Unlike conventional intake valve phase and lift system which controls all the cylinder intake valves simultaneously and in the same proportion; MultiAir, through the use of an electronically controlled " hydraulic link" between the camshaft and intake valve, allow for each intake valve to be controlled independently. The valve lift and timing can be adjusted infinitely

The MultiAir valve train has a mechanical camshaft lobe acting on a hydraulic pump located between the camshaft intake lobe and the intake valve. The pump provides oil under pressure to a two-way electro-hydraulic solenoid valve called the Variable Valve Actuator (VVA) Solenoid. The VVA Solenoid is electronically controlled during the specific intake cam lobe event by the Powertrain Control Module (PCM). During the event the VVA Solenoid is commanded to either hold oil pressure or bleed oil. The Variable Valve Actuator (VVA) Solenoid is a normally open solenoid. The PCM provides 12 volts to close the solenoid. The position of the VVA Solenoid determines the intake valve timing and lift. This change on valve action is similar to creating a change in the camshaft lobe profile affecting lift and duration of the valve opening.

The VVA high oil pressure absent monitor confirms proper operation of the intake valves by measuring overall intake manifold pressure, monitoring intake manifold pressure pulsations, and monitoring RPM fluctuations during engine cranking. The PCM compares the manifold pressure value, manifold pressure pulsations, and RPM fluctuations to threshold values. The basis of the monitor is that a lack of oil in the high pressure chamber of the solenoid valves will prevent the intake valves from opening. When this occurs, no air is brought into the cylinder during the intake stroke, and so there is no air to compress on the compression stroke. This will result in a lack of vacuum in the manifold, causing prevention the normal RPM and manifold pressure fluctuations that occur during compression and intake events. This condition can be diagnosed by an overall lack of manifold vacuum, a lack of intake manifold pressure pulsations, and a lack of RPM fluctuations during engine cranking. This monitor is enabled during cold starts when there are no active MAP Sensor circuit faults

- When Monitored:
Engine cranking. Engine Oil Temperature, Engine Coolant Temperature (ECT), Manifold Air Pressure (MAP), Barometer (Baro), Camshaft Position (CMP), Crankshaft Position (CKP), Intake Air Temperature (IAT) and boost pressure.

- Set Conditions:
Engine oil temperature less than or equal to 45°C (113°F), ECT less than or equal to 45°C (113°F), Engine Oil Temperature within 6°C (43°F) of ECT. No faults active related to MAP, Baro, CMP, CKP, ECT, IAT or boost pressure. Less than twelve intake manifold pulsations detected during engine crank.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. CHECK THE ENGINE OIL

NOTE: An active SKIM code can cause this DTC to set. This may happen because the PCM will turn off the actuation of the VVA Actuators, but is still monitoring the parameters of the VVA high oil pressure absent monitor. Diagnose any SKIM Module DTCs that are present before continuing with this test procedure.

NOTE: This code may not set if engine is warm, recommend allowing vehicle to sit for a cold soak.

NOTE: Engine must be cranked for approximately 10 seconds to set DTC.

1. Check the engine for the following:
- LOW ENGINE OIL
- INCORRECT OIL FILTER THAT DOES NOT MEET OEM SPECIFICATIONS
- OIL DIRTY OR DETERIORATED (Lack of scheduled oil changes)
- CORRECT VISCOSITY AND WEIGHT
- ENGINE OIL CONTAMINATED (i.e., coolant and/or fuel)

Is oil level, type, and condition correct?

Yes

- Go To 2

No

- Correct level/change engine oil and filter as required, consult the service information for correct type and grade of engine oil and repeat test.

2. CHECK OIL PRESSURE / ENGINE MECHANICAL

NOTE: The actuators will not operate if the oil pressure is too low or too high.

1. Remove the Oil Pressure Switch and install a mechanical oil pressure gauge.

2. Crank the engine for at least 10 seconds and check the oil pressure at the Oil Pressure Switch location.

Is the oil pressure between 0.8 bar (11.6 psi) and 7.5 bar (108.8 psi)?

Yes

- Go To 3

No

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. ENGINE MECHANICAL
1. Perform a cylinder leak down test.

Were any leaks found during the cylinder leak down test?

Yes

- Go To 4

No

- Inspect for a broken timing belt and/or bent or broken valves. Perform the appropriate repair.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. CHECK THE MULTI AIR OIL SUPPLY SCREEN
1. Remove the VVA Assembly oil supply filter screen and visually inspect for contamination or damage.

Was the screen damaged or plugged/restricted?

Yes

- Replace filter screen and test operation. Investigate for source of contamination.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 5

5. CHECK THE MULTI AIR OIL PRESSURE
1. Install a mechanical oil pressure gauge to the oil supply filter screen port.
2. Crank the engine for at least 10 seconds and measure the oil pressure.

Is oil the pressure above 0.6 bar (8.7 psi) and 7.5 bar (108.8 psi)?

Yes

- Go To 6

No

- Repair the cause of the lack of oil pressure to the VVA Assembly.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. CHECK THE PCM OUTPUT TO THE VVA SOLENOIDS
1. Using a 12-volt test light, back probe across the solenoid control circuit and return circuit of one of the VVA Solenoids.
2. Turn the ignition on.
3. With the scan tool, actuate the VVA Solenoid that has the 12-test light is connected to it.

Does the test light illuminate brightly when actuated on?

Yes

- Replace the Variable Valve Actuation Assembly.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- 7

7. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Engine Oil Pressure Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Sensor and Powertrain Control Module harness connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.