Tepi

Hi everyone

At first sorry for my English spelling.

I'm from Finland
I work as a Toyota/Lexus mechanic.(But I have very little experience of Lexuses. They are quite rare in our area)

I have a problem with Lexus LS400 ,prod.date 04/98.

Every morning when I jump into the car and start to drive, I can drive as far as I want with no problems, but If I take a brake (engine is now in normal operating temperature) for example at the gas station and drink one cup of coffee.
And then, when I start the car again and continue driving it takes everytime approx. 30 seconds and VSC-OFF light and CHECK ENGINE comes on.
Now If I turn ignition off and start the engine, after 30 sec. same thing happens again. I don't feel anything when the light hits, everything seems to work fine except I can't use VSC-system.

But if I clear codes (P1346 and C1201) with OBD2-tester, I can drive no matter how many miles if I don't take a break and turn IGN off.

Code P1346: VVT Sensor/Camshaft Position Sensor Circuit Range/Performance Problem (Bank 1)

Code C1201: Engine control system. System malfunction

Factory book says reason for code P1346 is jumping teeth of timing belt or faulty ECU.
But I must be absolutely sure before I order new Very expensive ECU. I don't have a chance to test with another ECU.

I have changed the timing belt and tensioner.
I have measured resistances and checked wire harshness, everything seems to be okay (except I'm not sure about crankshaft position sensor, because I couldn't find reference value. I measured 2,1 kilo ohms. Cam pos. sensor and VVT sensors were aprox. 1,3 kohms)
I have changed places between VVT-sensors, but code stays in Bank1.
I have tried new Oil Control Valve for VVT in Bank1.
And I don't believe in any bad contacts because of the nature of malfunction, warm engine and TIME after re-start seems to be the main points.

Have you ever experienced this kind of problem ?
If you have any advice, please help me.

Thanks, Tepi

Tepi

VVT-i

Tepi..look like you got a tough one here. It will be easier if you have another LS to swap the ECM and try it. Do you have the technical hot line in Europe? I had this problem on the RX( Harrier) with V-6, but turn out to be Oil control valve, but you already replaced the Oil control valve.

fire

Sounds like your cam timing is off via timing belt change, huh? VVT-i timing belt changes can be tricky.

This is a range/ performance problem, not an open/ short problem. There should be a separate code for open/ short, so your wiring harness, sensors, and ecm seem to be working fine. I guess it would be possible that a VVT-i actuator could be stuck, but they are easily tested (turned on and off with a noticeable harsh running at idle).

Sooner

i agree with fire your belt is probably off

fire

go bulldogs!

VVT-i

He said he'd already change the timing belt, but the code still the same( from my understanding).

Sooner

my bad i see that now

Tepi

Timing belt is okay....

I have tested VVT-actuators with OBDII-tester (Active test)
Both sides sounds ok.

ndmeyer2

Tepi

Did you ever figure out what was wrong with your lexus. I have the same exact problem, and I replaced the timing belt and switched the vvt-i sensors, and it stays in the same bank. Also, what type of scan tool did you have to use to test the vvt-i actuator. I have an Actron CP9185.

Tepi

Problem was in vvt actuator. With the new actuator replaced no codes showed up.
Scan tool is Toyota Intelligen Tester. Active test for vvt is just instant retard for timing to give rough idle or to make engine stall. It just gives you a hint does the actuator response anyhow.
In this case we just had to test with the new part and found the problem.