The CVVT (Continuously Variable Valve Timing) system built on the camshaft helps the engine decrease the exhaust gas and increase engine power and fuel economy by changing the valve open/close timing of the camshaft continuously. The valve control solenoid, the main control part of the CVVT, changes the direction of the oil path through the CVVT by the duty control of the PCM and changes the open and close timing of the intake and exhaust valves.
PCM sets DTC P0079 if the PCM detects that the exhaust valve control solenoid control circuit is short to ground.
Item
Detecting Condition
Possible Cause
DTC Strategy
Electrical Check
Short to ground in control circuit
Poor connection or damaged harness
Faulty Exhaust Valve Control Solenoid
Enable Conditions
10V < Battery voltage < 16V
Threshold Value
Short circuit to ground or open circuit
Diagnostic Time
2 sec.
Mil On Condition
2 Driving Cycles
Intake OCV
Normal Parameter
Insulation Resistance (?)
Above 50 ?
Temp.(?)
Resistance(?)
0
32
6.2 ~ 7.4
60
140
8.0 ~ 9.2
10
50
6.5 ~ 7.7
70
158
8.3 ~ 9.5
20
68
6.9 ~ 7.9
80
176
8.6 ~ 9.8
30
86
7.1 ~ 8.3
90
194
8.9 ~ 10.1
40
104
7.4 ~ 8.6
100
212
9.2 ~ 10.4
122
7.7 ~ 8.9
Set up an oscilloscope as follows :
Channel A (+): Signal terminal of the CMPS #2(back probe), (-): ground
Channel B (+): Signal terminal of the CKPS(back probe), (-): ground
Start the engine and check for signal waveform compared with reference waveform as below.
A : CMPS and CKPS waveform of exhaust shaft at idle
B : CMPS and CKPS waveform of exhaust cam shaft at acceleration
(Tooth number is changed by CVVT operation)