Theory of Operation
Variable Cam Timing (VCT) allows the Powertrain Control Module (PCM) to monitor and adjust the position of the camshaft, based on desired torque levels and engine operating conditions. The camshaft design allows for the exhaust lobes to be adjusted while the intake lobes are not adjustable all on one camshaft. The PCM controls a solenoid operated control valve, that is used to direct oil pressure to hydraulic actuator mounted between the camshaft and its driving sprocket. The oil pressure alters the angular position or phasing of the camshaft relative to crankshaft rotation. A sensor is used to monitor the position of the camshaft.
- When Monitored:
Variable Cam Timing (VCT) phasing accuracy is monitored under the following conditions: (1) Engine speed is at least 150 rpm; (2) No CMP sensor or CKP sensor plausibility errors. This is performed even when phasing control is not enabled, to verify the actuator is keeping the camshaft at the default (lockpin) phase.
- Set Condition:
The actual measured camshaft phase does not match the desired camshaft phasing set point. Two Trip Fault. Three good trips to turn off the MIL.
Possible Causes |
|---|
| ENGINE OIL DIRTY OR CONTAMINATED |
| INCORRECT ENGINE OIL VISCOSITY |
| INSUFFICIENT ENGINE OIL PRESSURE |
| (K442) CMP CONTROL CIRCUIT OPEN OR SHORTED |
| (Z908) SOLENOID GROUND CIRCUIT EXCESSIVE RESISTANCE OR OPEN |
| CAMSHAFT POSITION SOLENOID (VARIABLE CAM TIMING SOLENOID) |
| CAMSHAFT PHASER |
| IMPROPER ASSEMBLY OF CAMSHAFT/CRANKSHAFT TIMING CHAIN AND SPROCKETS |
| ENGINE OIL PRESSURE SENSOR OR CIRCUIT |
| ENGINE OIL TEMPERATURE SENSOR OR CIRCUIT |
| HIGH FRICTION IN CAMSHAFT OR OTHER VALVETRAIN COMPONENTS |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
1.
DTC IS ACTIVE
| NOTE: | Diagnose and repair P0013 Bank 1 Camshaft 2 Position Actuator Circuit Open DTC before continuing. |
| NOTE: | Diagnose and repair any Crankshaft-Camshaft Timing Misalignment DTCs before continuing with this test. |
| NOTE: | Diagnose and repair any Oil Temperature Sensor DTCs before continuing with this test. |
| NOTE: | The most likely cause for this DTC to set is high friction in the valvetrain components such as the camshaft and valve springs. |
| NOTE: | If this code has set with less than 1000 miles on the odometer the cause of the code may be that the engine assembly is tight and the engine needs time to loosen up. |
| NOTE: | Diagnose and repair any system voltage DTCs before continuing with this test. |
| NOTE: | Diagnose and repair any CMP Sensor or CKP Sensor DTCs before continuing with this test. |
| NOTE: | Diagnose and repair any oil pressure or Oil Pressure Sensor DTCs before continuing with this test. |
| 1. | Start the engine and allow it to reach normal operating temperature. |
| WARNING: | When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result possible serious or fatal injury. |
| 2. | With the scan tool, view DTCs and read and record the related Freeze Frame data. |
| 3. | With the scan tool, Clear DTCs in the Powertrain Control Module (PCM). |
| 4. | Test drive the vehicle under the conditions in which the DTC is monitored, as outlined above. |
| 5. | With the scan tool, select View DTCs. |
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION Diagnostic Procedure.
2.
CAMSHAFT POSITION SOLENOID CLEANING
| 1. | With the scan tool preform the Exhaust Phaser 1 Cleaning function |
Did the DTC reset?
Yes
- Go To 3
No
- Perform the INTERMITTENT CONDITION Diagnostic Procedure.
3.
ENGINE OIL DIRTY OR CONTAMINATED
| 2. | Inspect engine oil for signs of contamination, sludge or foreign material. |
| NOTE: | If the engine oil is contaminated, inspect the Camshaft Position Solenoid for contamination, foreign material or any condition that would restrict movement of the valve. The solenoid must be replaced if it is damaged or if valve movement is restricted due to contamination. |
Were any problems found?
Yes
- Clean the engine oil system, including oil passages.
- Perform the POWERTRAIN VERIFICATION TEST.
No
- Go To 4
4.
ENGINE OIL PRESSURE
| 2. | Check the engine oil pressure in accordance with the Service Information. |
| 3. | Using the scan tool, compare the engine oil pressure reading you get off of a gauge and compare that reading to what the scan tool displays with the engine running. If the pressure reading on the scan tool is not close to what the gauge displays, perform the diagnostic procedure for P0521-ENGINE OIL PRESSURE SENSOR PERFORMANCE. |
Is the engine oil pressure within the specifications outlined in the Service Information?
Yes
- Go To 5
No
- Inspect and repair the cause of the low oil pressure condition.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
5.
INCORRECT ENGINE OIL TEMPERATURE READING
| 2. | Using a scan tool monitor the engine oil temperature and compare the engine oil temperature to the Engine Coolant Temperature value. |
Does the Engine Oil Temperature seem excessively high or low as compared to the Engine Coolant Temperature?
Yes
- Perform the diagnostic procedure P0196-ENGINE OIL TEMPERATURE SENSOR PERFORMANCE for further assistance.
- Perform the POWERTRAIN VERIFICATION TEST.
No
- Go To 6
6.
INCORRECT ENGINE OIL VISCOSITY
| 1. | Review service history to determine if the correct viscosity engine oil was used. |
Were any problems found?
Yes
- Change the engine oil in accordance with the Service Information and retest.
- Perform the POWERTRAIN VERIFICATION TEST.
No
- Go To 7
7.
CAMSHAFT POSITION SOLENOID CONTROL ACTUATION
| NOTE: | The Camshaft Position Solenoid actuates whenever the ignition key is turned on for cleaning purposes. This actuation also take place when the engine stops. So if you are testing the solenoid with a test light it is possible that you will see the solenoid actuate at key on and engine stop. |
| 2. | With the scan tool, actuate the Camshaft Position Solenoid control to toggle on and off. |
| 3. | Listen for the Camshaft Position Solenoid to click open and closed during the actuation. |
Does the Camshaft Position Solenoid click open and closed during the actuation?
Yes
- Go To 11
No
- Go To 8
8.
EXCESSIVE RESISTANCE OR SHORT TO GROUND IN THE (K442) VCT CONTROL CIRCUIT
| 2. | Disconnect the Camshaft Position Solenoid (Variable Cam Timing Solenoid) harness connector. |
| 4. | With the scan tool actuate the VCT Solenoid. |
| 5. | Using a 12-volt test light connected to ground, probe the (K442) CMP Control circuit in the Camshaft Position Solenoid harness connector. |
| NOTE: | The test light should be off unless you have a short to ground. |
| 6. | With the scan tool, actuate the Camshaft Position Solenoid (VCT Solenoid DC) control to the ON position. |
| NOTE: | The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery. |
Is the test light illuminated and bright during the actuation and was it off when required?
Yes
- Go To 10
No
- Repair the excessive resistance or short to ground in the (K442) CMP Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST.
9.
EXCESSIVE RESISTANCE OR OPEN (Z908) SOLENOID GROUND CIRCUIT
| 2. | Measure the resistance of the (Z908) VCT Solenoid ground circuit from the VCT Solenoid harness connector. |
Is the resistance below 5.0 Ohms?
Yes
- Go To 8
No
- Repair the excessive resistance or open in the (Z908) VCT Solenoid ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST.
10.
CAMSHAFT POSITION SOLENOID
| 2. | Inspect the wiring and connectors between the Camshaft Position Solenoid (Variable Cam Timing Solenoid) and the Powertrain Control Module (PCM). |
| 3. | Look for any chafed, pierced, pinched or partially broken wires. |
| 4. | Look for broken, bent, pushed out or corroded terminals. |
| 5. | Verify that there is good pin to terminal contact in the Camshaft Position Solenoid and Powertrain Control Module connectors. |
| 6. | Remove the Camshaft Position Solenoid (VCT Solenoid) in accordance with the Service Information. |
| 7. | Inspect the Camshaft Position Solenoid (VCT Solenoid) for contamination, foreign material or any condition that would restrict movement of the valve. |
| NOTE: | The solenoid must be replaced if it is damaged or if valve movement is restricted due to contamination. |
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST.
No
- Replace the Camshaft Position Solenoid (VCT Solenoid) in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST.
11.
CAMSHAFT PHASER
| 2. | Remove the Camshaft Phaser in accordance with the Service information. |
| 3. | Inspect the Phaser for contamination, foreign material or any condition that would restrict operation of the Phaser. |
| 4. | Inspect the Phaser oil passages for signs of sludge or foreign material. |
| NOTE: | The Phaser should not be disassembled. If the Phaser is damaged, it must be replaced. |
Were any problems found with the Camshaft Phaser?
Yes
- Replace the Camshaft Phaser in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST.
No
- Go To 12
12.
HIGH FRICTION IN THE VALVETRAIN COMPONENTS
| 2. | Remove the Camshaft in accordance with the Service information. |
| 3. | While removing the components to remove the Camshaft inspect the rocker arms, valve springs and pushrods that may cause an increase in the torque to rotate the camshaft. |
| 4. | Inspect the camshaft and camshaft bearings for any signs of excessive wear. |
Were any problems found with the camshaft or any other valvetrain components?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. .
No
- Replace the Powertrain Control Module (PCM) in accordance with the Service Information.
- Perform the POWERTRAIN VERIFICATION TEST.
