dwafford

'06 SC430 was running fine. One day noticed a misfire. Scan showed misfire cylinder 5. Checked plug, wiring, coil, found no problem. Next day, running very rough, scan showed misfire cylinders 1, 3, 5, 7. A couple of days later, the engine wouldn't start at all, scan showed faults in both cam position sensor and crankshaft position sensor circuits. Didn't really believe this because of the progressive nature of the faults, but replaced the cam position sensor anyway. No change. Hesitate to change the crank position sensor. Acts like immobilizer has been activated: engine starts and runs for 1 sec, then shuts down. Many thanks for suggestions.

VVTiBob

Can you provide us the actual DTC codes that showed up? Potential problem areas are:

• Engine Wire
• Connectors
• Vacuum hoses/connectors
• Ignition system
• Fuel Pressure
• MAF Sensor
• Coolant Temp Sensor
• Compression Issues
• Valve clearance and timing issues
• PCV hose
• ECM controller

To name a few.

Has the Check Engine light come on? If so, is it solid or blinking? The one component consistent with all the failure you've cited is the ECM... but it difficult to tell with the info you've provided.

VVTiBob

BTW Since you asked the identical question in the "Engine Immobilizer" thread I deleted that thread and merged them together.

dwafford

In addition to the cylinder misfire codes that were set while the engine was still running (P0301, 03, 05, 07), the codes that I read when the engine failed to start were P0335 and P0340 (I think. I didn't write these down, but when I read the DTC code descriptions, these are the two I remember seeing).

I agree with your statement that a number of components and/or systems could cause this failure, but I'm hoping perhaps there's something in the progression of faults that occurred (cyl 1 misfire, then all of left bank cyl misfires, then cam position sensor and crankshaft position sensor) that might point to a common cause.

Regarding your comment about the VVT solenoid, if that failed, shouldn't it have set a VVT fault code? And about the ECM, that was an early suspect. I removed it and sent it to a place in Texas that tests them, and they sent it back with a clean bill of health.

I read a technician post recently that said if the engine immobilizer was set (I had thought this might be a possibility), the engine would crank but not start at all. This engine starts and runs for 1 second or less, then dies. Do you agree this could not be the immobilizer?

I had also considered the possibility of a fuel pump failure, but if that was the case, I think after a few tries the fuel lines would be completely empty, and the engine wouldn't run even momentarily.

I saw another post that described similar symptoms, and the cure turned out to be cleaning the VVT OCV. Do you think that might be a possibility?

I consider it wildly improbable that there's any connection, but just in case, just about the same time the engine started acting up, the retractable top also stopped working correctly. I can get it to cycle only by repeatedly pushing the switch many times (15-20 or so), with it moving only a tiny bit with each repeated push of the switch - and even then, when the top goes up, the quarter windows do not.

Thanks again for your help. Hope I can return the favor to someone on here someday.

Jabberwock

So your engine won't run and your top won't cycle? I wish I could be more helpful in terms of technical repair info but my worry would be that the two failures are interconnected, if it were me and my car was basically bricked - I'd call a tow truck and get it to Lexus. Pay them to at least diagnose the problem.

VVTiBob

The common thread so far in the DTCs you've mentioned is the ECM, yet you've said it passed what ever test was done to it. Have you inspected the wire harness and connectors to the ECM?

The next steps in the FSM will be to break out the volt/ohm meter and begin testing components and connections to the ECM, But at this point I'm with Jabberwock, time for a thorough diagnostic at your local dealer or with a Lexus master mechanic.

talwang

iTrader: (4)

The issues you have more likely require a Lexus trained mechanic/technician with some Lexus diagnostic tools to perform the job properly.
Most shops won't spend that much on diagnostic tools that can get all of you Lexus specific codes.