Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnosis & Repair (Using Lexus Scan Tool)
2004 Toyota Celica GT, StandardSECTION Diagnosis & Repair (Using Lexus Scan Tool)
WARNING: This page is about a different car, the 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
- Using scan tool, select ACTIVE TEST mode. Note idle speed when OCV is activated by scan tool. If idle speed is normal with OCV off and engine idles rough or stalls when OCV is on, VVT is functioning properly at this time. Fault is intermittent. DTC may have been set because of a foreign object that was temporarily caught in the engine oil system but after a short time system returned to normal. If idle speed does not function as specified, go to next step.
- Start engine and allow it to idle. Disconnect suspect Oil Control Valve (OCV). Using jumper wires, apply battery voltage and ground to OCV. Engine should idle rough or stall. If OCV operates as specified, go to next step. If OCV does not operate as specified, replace OCV.
- With engine idling, check voltage to OCV. If checking OCV for bank No. 1 (right cylinder head), backprobing, connect oscilloscope between ECM E8 connector terminals No. 13 (Blue/White wire) and No. 14 (Blue/Red wire). See Figure. If checking OCV for bank No. 2 (left cylinder head), backprobing, connect oscilloscope between ECM E8 connector terminals No. 15 (Green/Red wire) and No. 16 (Green/Black wire). On all applications, ensure oscilloscope pattern is as shown. See Figure. As engine speed is increased, waveform frequency ("A") should lengthen. If waveform pattern is as shown, go to next step. If waveform pattern is not as shown, replace ECM.
- Check for an open or short circuit in wiring harness between suspect OCV and ECM. Repair wiring harness as necessary. If wiring harness is okay, fault is intermittent.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.