Lexus Repair Questions? Ask a Mechanic for Answers ASAP
I was just about to call it a night when your question popped up. They're probably only about three or four of us on here that would be able to handle this type of question. Are you a shop or a private owner? Do you have ociliscope and have you tested to see if the OCV is receiving a signal or checked the pattern on ociliscope? This is a duty cycle square wave pattern. If you have an active testing scan tool if you activate the advanced timing does the engine idle rough or stall?
The VVT system constantly adjusts intake valve timing based upon operating conditions. The ECM system controls the Oil Control Valve (OCV) with a variable duty cycle. The Oil Control Valve then supplies oil to the advance or retard side of the VVT Controller (actuator on the cam shaft itself). The oil applied to the VVT Controller will cause the intake cam to advance or retard depending on the position of the Oil Control Valve. The ECM verifies that the desired camshaft angle has been achieved by monitoring the camshaft position sensor. If anything has happened to the camshaft position sensor enough to screw up the signal but yet not enough to set a code for open or short or if a timing belt has been on this car recently there could be issues with the wiring going to the sensor or the timing belt. If these factors can be ruled out then you're probably looking at the VVT controller sticking or binding not returning back on a retarded or advanced signal.
Verify the duty cycle signal to the OCV and if you power up the OCV can you make the actuator/controller stall the engine or make it run rough ? Let me know you find I can follow up with you later tomorrow.
I am a former mechanic, out of the industry for about 20 years, but still dabble with it from time to time. I do not have an ocilloscope. I did see the waveform you were referring to though. Not sure how i'll check that. So if i'm reading you correctly, I'm looking at: 1) OCV signal, 2)Cam sensor, and 3)sticking/binding VVT controller. Just wondering about the Cam sensor....how often do those fail? I'll check into that tommorow in the AM. I'll get to you with some results hopefully. This is holding up my registration, and getting very frustrating.
1,2 and 3 are correct. If you do not have access to an oscilloscope if you have a digital voltmeter that does percent or milliseconds on time you can also check to see if you're getting a signal pulse that way also. How the solenoid is controlled by the computer sending the 12 V signal or supply out through the solenoid windings and then back to the computer. The computer pulses the ground there by energizing on time of solenoid. It is based to the same principle as an injector functioning. The on time determines how much oil pressure is applied to the back of the actuator on the camshaft. Normally when you have this code specifically set it usually is focused in on the OCV or the actuator. If you had an issue with a camshaft correlation timing code I would be more focused on the cam sensors or the wiring going to it. The cam sensors themselves normally are not an issue usually it is the wire going to it that gets damaged by the timing belt or the cover or installation procedures. Let me know what you find.
Thanks. What I'm thinking though, I really don't think the cam sensor should be an issue, its located at the back of the head near the firewall away from possible damage. It was only removed once when I rebuilt the engine. I know it could fail. but it seems unlikely to me. If it is sending a signaI to the ECU to turn on 1349, that sounds like it works. I suppose since I replaced most everything else I could replace this too. Is there a test method to determine failure?
I'm leaning towards the Controller assembly. After reading and investigating the message boards last night, it looks like this trouble code causes a lot of problems for owners and techs alike. It took a 3rd tech to confirm there was a filter//screen behind the OCV after 2 told me there wasn't. Both local Lexus dealers usually have to special order a large percentage of parts that I need, but both had this part sitting on the shelf. Kinda leads me to believe this controller assembly is the root of all evil in regards XXXXX XXXXX VVT system.
As I said , I'm just frustated as the car runs perfectly, has great power and acceleration, doesn't misfire, and PASSES the actual emissions test, but fails because of the MIL light being on.
Also, what direction does oil travel to the VVT system. There is an oil pipe the runs to the OCV housing assembly. Does it not travel through the head and cam to the OCV, or does it travel from the base of the block up the the OCV? There are two bolts at each end of the pipe and the upper one has a check valve in it. If I mistakenly had them switched positions, that would create a possible oil restriction? I'm sure they are in the correct position, but I don't want to miss anything.
To answer your question the easiest way to test if the actuator is working is by fully engaging the OCV solenoid so that maximum advance or retard is affected on the camshaft this can be done either by grounding the negative side of the OCV solenoid thereby engaging the solenoid to open fully and this should in turn cause the engine to run rough. Ideally if you have an active testing scan tool this will be easier to do and safer to do. If you apply full advance or retard pressure to the actuator and the engine does not run rough then there is either a blockage in the oil passage to the actuator or the actuator itself is stuck. I would probably tend to agree with your analysis that the common denominator is the actuator controller itself. But due to the price of the part it is always best to confirm whether or not you can physically make the actuator goal by applying full hydraulic pressure to it. As far as a line in the check valve I don't recall on that location. The oil is fed to the oil control valve, the control valve supplies pressure through the cylinder head to the camshaft journal/ and then to the actuator. I was looking for the actual oil flow chart but was unable to find it this time if you still need that I will continue to look further.
Ideally they need to check that signal with an oscilloscope. Let me know what you find.
Are you online still?
OK, here is what I found. The other mechanic had an active scanner, as it looks as though what I have is a read only program. He tried to shut off the OCV and the vehicle had no response at all. So he disconnected the connector to the OCV and tested it with a bulb. No light appeared, even when he retried the test with his scanner. So it looks like a voltage/wire problem. The wire into the connector is brittle for about 1" or so as would be expected from constant exposure to the engine. So this evening I started following the wire into the harness. A real pain as I'm sure you know, exposing and tracing the wire with about 30-40 other wires mixed together through the harness. I had to leave for about 3 hours, and when I returned I reconnected the connector to the OCV and checked again for voltage with the engine running. I measured at the back of the connector where the wire goes into the connector and found about 7 volts. So I disconnected it and tried to measure inside the connector and got no voltage, so reconnected and remeasured at the back and again, no voltage. So at this point I figured I may have broken connection inside the wire. I went about 5" down the wire and made a small notch on the outside to expose the smallest amount where I could ge a reading, and again, no voltage. So, back to removing and exposing more of the harness I went. Like I said a real pain, especially trying not to cause damage anything else along the way. I got about another 6" further along and decided to test again. Again I did get about 7 volts at the back of the connector, and 2 small test areas. So it looks like it could be a bad connection somewhere. There is about another 8 inches or so of unexposed wire before the harness makes it into the ECU. I saw your messages and thats where I stopped. I still want to test the inside of the connector to the OCV again and may do that in a little while.
Another question, if the cam sensor has failed and doesn't send a signal to the ECU, will the ECU still send a signal to the OCV?
Hoping to hear form you in a bit.
I was on pretty late last night but I must have just missed you based on the time of your reply. I believe that you're on the right track I think at this point what I would do is bypass the 2 wires. Come directly out of the computer as close as you can get to the connector and apply these to the OCV solenoid directly and see if you correct the problem. The only thing you need to do is make sure that the connection in the connector at the computer is tight. You need some type of pin fit gauge or another connector that's the same size pins in order to feel how snug the connector is As far as the metal portion of the wire end. As far as whether or not the computer would not send a signal out if the can sensor was not functioning it's probably not likely if it was that bad it would trigger a cam sensor code as open or short signal. I had never actually disconnected to simulate this kind of scenario but I would think the computer would continuously try and duty cycle the solenoid.
The Solenoid should have 12 V and computer duty cycles that 12 volt signal and is a square wave. If you're only getting 7 V and that is intermittent that indicates high resistance in the wire or a loose pinch hit. I would run 2 separate wires to the solenoid from the computer directly and see if the problem goes away. The other option is you can test for continuity from the computer to the OCV connector but sometimes resistance checking does not tell you the whole story.
I will be monitoring on off most of the day tomorrow I'll get back to you. Let me know how things progress.
Did you get the $15.00, I think I sent it, but i'm still not sure how all this works yet.
Yes the accept has been received.
You should have 12 V coming out of the ECU. If you test the other bank it will verify this. This is definitely an unusual one I've never seen one fail and only put out 7.4 V from the ECU. I've never done this as a test but you might consider trying bringing 12 V from the battery and probing it into the back of the 12 V lead on the OCV solenoid so that 12 V is going back to the computer and solenoid and see if this will fool the computer and allow it to duty cycle the other wire that is the ground circuit going back to the computer. Understand this is truly an experiment at this point and were assuming that the computer is not capable of sending 12 V out the line that you're just not tested. Let me know if you decide to try this and what happens with the end result. Check the other duty cycle valve for 12 V and if you can read the duty cycle on the ground side of that solenoid. Before this little experiment. Proceed at your own risk.
The voltages should be the same at 12 V. I would not be too concerned about the shock factor of the ECU. If you get an ECU for a couple hundred bucks it might be worth the risk. The ECU is strictly solid-state no moving parts. You might find one for wholesale prices by going to www.mylexparts.com I'm always up for a challenge but I'm not sure where you're located wouldn't mind taking a look at this weird problem myself.
This is just a thought but what if you disconnected or clipped the wire that supposed to have 12 V coming out of the computer so you had no voltage feedback into the computer and the jumper wire from the battery with 12 V merely went through the solenoid then back to the ground side of the computer it wouldn't matter on the ground side of the computer because the computer is only going to duty cycle that. Unless the computer is looking for a load on that positive side and that's how it measures a pulse but I would think it would be looking at the ground side. Unfortunately that information is not available to wiring diagrams and information only shows the wire going to the computer not what goes on inside the computer anymore. Just a thought.
Yeah, I'm in southern Calif. I really can't afford anything but a used ECU at this point anyhow, but haven't been able to find anything yet. Well, anything local, there was one a russian website and had to use a translator to dechipher the description, but not sure if its an exact fit. Are there any cross references for ECU's? Also, I inquired at Lexus about a wiring diagram and they said they weren't available for public purchase. Don't know if I believe that, but i'll have to try a different dealer.
Do you have any diagrams for dash, removal? After this mess, I have to replace my heater core. Can't wait for that fun.
Do you know if you can paste pictures and diagrams in this forum?
Shoot this guy an email toyotaXXX@XXXXXX.XXX give him the computer number and see what he can do. Let me see what diagrams I can find.
Did you shoot XXX@XXXXXX.XXX the info? Try this guy on ebay he rebuilds RAV4 ecu's maybe he can do something with yours? Send him an email also.
I have read through most of our exchanges and some of that I have forgotten due to the time and how many questions I have done since then. Have you tried to make a new sub wire harness going directly from the OCV into the two inputs/outputs directly at the engine control computer to rule out any wiring issues? At this point if you have a brand-new Lexus computer and a new Lexus OCV and actuator this only leaves a wiring issue being shorted or having corrosion/resistance in it. Also when you're checking these voltages are you back probing the connector at the OCV while the vehicle is running and everything plugged in and intact?
So essentially you have bypassed the harness like I talked about above and the problem appears to be fixed correct?
Let me know.
Did you completely bypass the factory harness with a sub harness i.e. two wires coming from the OCV and going directly to the ECU correct pins? the only other thing I can suggest and this would require a two channel oscilloscope, would be to monitor the camshaft position sensor in correlation to the crankshaft position sensor and monitor the waveforms to see if the cam shaft is truly changing when the OCV commands and two. Then again if you're still not getting the correct voltage and duty cycle waveform from the OCV that test isn't a matter. Have you had the ability to or your friends have the ability to monitor the ground side of the OCV to see what exactly is going on using an oscilloscope?
I would reconfirm if you can the cam position sensor correlation to the crankshaft position sensor and see if you're getting any fluctuations and especially monitor the duty cycle of the OCV ground side going back to the computer. I have to assume that when you installed the actuator onto the cam shaft that it is done correctly and there was nothing sticking or binding in the actuator. Other than that I'm kind of the loss for words or explanations. When you apply full on pressure the vehicle should stumble if the actuator is fully advancing and retarding like it is supposed to.