Fault Phenomenon

A Toyota Crown sedan with approximately 120,000 kilometers on the odometer, fitted with a 3GR engine, presents the following faults: the engine malfunction indicator lamp illuminates, and the vehicle suffers poor acceleration.

Troubleshooting

Road test the vehicle and retrieve DTCs. The fault codes indicate defective components related to the bank 2 (cylinders 2, 4, 6) camshaft timing control on the right side of the engine compartment, triggering DTCs P0017 and P0022. Combined with the vehicle’s driving symptoms, potential root causes are analyzed as follows:

1.Intake system air leakage

2.Malfunction of mass air flow sensor and its wiring harness

3.Faults in ignition timing and components of the bank 2 camshaft timing control system

To verify the fault symptoms, the engine idles up to 1400 RPM and is limited to a maximum of 3000 RPM. DTCs P0017 and P0022 are stored and output by the PCM when a significant deviation occurs in the engine VVT timing control system. Even if the system returns to normal within a short period, these DTCs will still be logged.

Therefore, technicians retrieved live data streams related to VVT control while the fault was present, and performed actuation tests on all VVT control components.

The test results reveal sticking within the camshaft VVT timing adjustment system. Technicians performed linear control actuation adjustments for the Variable Valve Timing (VVT) system, yet no changes were observed in the actual rotational position of the VVT assembly. The fault scope is further narrowed down, and the primary root causes are analyzed as follows:

1.Malfunction of the camshaft position actuator solenoid valve (OCV)

2.Contaminated engine oil clogging the solenoid valve filter screen

3.Oil pressure leakage caused by worn impeller inside the camshaft position actuator (VVT gear sprocket)

Verify the status of each component separately to further pinpoint the fault. Perform an energization test on the solenoid valve:

The solenoid valve operated normally when energized, which largely rules out the solenoid valve as the root cause. Technicians then inspected the oil supply pipelines of the VVT timing components and finally located the fault: the oil supply filter screen of the VVT control oil passage was clogged with contaminants.

After this, technicians replaced the brand-new VVT oil passage filter screen, and the fault was eliminated.

Fault Mechanism

Based on the above troubleshooting process, the root cause is deduced as follows:

Once the VVT oil passage filter screen becomes clogged, the oil flow through the VVT oil channel is insufficient. During acceleration, the solenoid valve activates to delay exhaust valve closing. When the engine returns to idle speed, the camshaft timing needs to adjust back to the maximum advance position (initial position) to reduce valve overlap angle and stabilize idle operation.

However, due to insufficient oil pressure and flow inside the VVT oil passage, engine oil cannot flow into the advance oil chamber of the VVT actuator assembly. As a result, the camshaft remains held at the retard side. This mismatch between the actual camshaft phase and the target set phase triggers the engine malfunction indicator lamp.

Since the filter screen is only moderately contaminated, the resulting change to the valve overlap angle is minor, which does not disrupt idle stability and eliminates rough idle symptoms. Nevertheless, the ECU detects the timing deviation fault and illuminates the malfunction warning light.

Case Summary

There are numerous DTCs related to VVT systems, such as P0010, P0011, P0012, P0013, P0014, P0016 and P0017, which tend to be complex to repair. As a technician, the fundamental principle is to troubleshoot step-by-step from simple to complex and conduct targeted inspections when the root cause remains unidentified.

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