The CVVT (Continuously Variable Valve Timing) system is installed to the chain sprocket of the intake camshaft. This system controls the intake camshaft to provide the optimal valve timing for every driving condition. The ECM controls the Oil Control Valve(OCV), based on the signals output from mass air flow, throttle position and engine coolant temperature. The CVVT controller regulates the intake camshaft angle using oil pressure through the OCV. As result, the relative position between the camshaft and the crankshaft becomes optimal, and the engine torque improves, fuel economy improves, exhaust emissions decrease under overall driving conditions.
DTC DESCRIPTION
Figure1. illustrates the method for detecting unresolved phasing steady-state error.
The figure shows two cases, case 1 to the left of the dashed line, and case 2 to the right of the dashed line. In case 1,the duty cycle command is considered high, or above a calibration threshold memorized in PCM. This should cause the cam phaser to move toward the maximum position, but the position remains at a medium level. The range of positions considered ‘medium’ is defined by calibrations.
In case 2, the duty cycle command is considered low, or below a calibration threshold memorized in PCM. This should cause the cam phaser to move toward the minimum position, but the position remains at a medium level.
Each of these cases is a phaser position error failure. Each case is also considered to be due to a phaser seizure. When either case is detected, a timing counter begins to increment. If the counter exceeds a calibration threshold memorized in PCM, the failure criteria is TRUE.
Another similar diagnostic test is performed to check steady-state error. In this test, no consideration is given to the duty cycle command versus phaser position. This test is only a check of the phasing position error. In the test, if the phaser error is greater than a calibration threshold memorized in PCM,a timing counter increments. If the counter exceeds the calibration threshold memorized in PCM,the failure criteria is TRUE.
PCM monitors CAM phaser error while both cam offset is available and cam velocity is below 15CAD/s .If the CAM phaser does not move although PCM commands OCV duty cycle, PCM determines that a fault exists and a DTC is stored.
DTC DETECTING CONDITION
Item
Detecting Condition
Possible cause
DTC Strategy
●
Determines if the phaser is stuck or has steady-state error
●
Engine Oil
●
OCV
●
CVVT stuck
●
PCM
Enable Conditions
●
Offsets available
●
Cam velocity below threshold〈 15 CAD/s
Thresh old value
Case 1
●
5 CAD 〈 Cam position〈 50 CAD
●
Duty Cycle 〉90%
●
Duty Cycle〈 10%
●
Timing Counter 〉80
Case 2
●
Cam Position error 〉15 CAD
●
Timing Counter 〉80
Diagnosis Time
●
Continuous
(More than 0.75sec. Test failure for every 90sec tests)
MIL On Condition
●
2 Driving Cycles
SCHEMATIC DIAGRAM
SIGNAL WAVEFORM AND DATA
MONITOR DTC STATUS
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4)
Read "DTC Status" parameter.
(5)
Is parameter displayed "Present fault"?
▶ Go to "System Inspection" procedure.
▶ Fault is intermittent caused by poor contact in the sensor’s and/or PCM’s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
SYSTEM INSPECTION
1.
Visual Inspection
(1)
Check oil level is O.K.
(2)
Check oil is contaminated.
(3)
Has a problem been found ?
▶ Repair or replace as necessary and then, go to " Verification of Vehicle Repair" procedure.
▶ Go to "Component Inspection" procedure.
COMPONENT INSPECTION
1.
Check OCV
(1)
Connect scantool and IG "ON"
(2)
Select "OCV" on the Actuation Test
(3)
Activate "OCV" by pressing "STRT(F1)" key
(should hear a faint click from Oil Control solenoid Valve)
(4)
Repeat this procedure 4 or 5 times to ensure reliability
(5)
Has a problem been found ?
▶ Substitute with a known - good OCV and check for proper operation. If the problem is corrected, replace OCV and go to "Verification of Vehicle Repair" procedure.
(6)
▶ Substitute with a known - good CVVT and check for proper operation. If the problem is corrected, replace CVVT and go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2.
Using a Scantool, Clear the DTCs
3.
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
4.
Monitor that all rediness test have been verified as " Complete "
5.
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
