So I FINELY got done fixing my misfire in cylinder 4! And I was so freaking happy that the car was running great, but I decided to crack open the top and check the valves one last time after a trip to work and back to make sure they were all still within spec, while I was at it I changed the oil and filter.

After checking and seeing that everything was in order and in spec, I threw it all back together and start her up and the check engine light comes on, car is starting but idling like crap and has a 340 code, camshaft position sensor circuit malfunction code.... I figured that maybe I bumped the front sensor while screwing the filter on so I changed it, but it is still failing, I have continuity at the connector pins but I can't seem to find the rear position sensor though it seems very unlikely that it would fail for no reason. Could the crankshaft position sensor cause this code to pop? If so, where is that sensor as well? Any ideas would be much appreciated.

My original problem, that was fixed:
https://www.clublexus.com/forums/es3...numbering.html

 

There is no rear camshaft position sensor. The sensor is a reluctance pickup, which is just a wire coil that generates a voltage as the teeth on the camshaft rotate past it. The sensor should read app 1 to 1.5 k ohms. When using the DVM you need to pay close attention to the multiplier, because it is more important than the digital reading itself. Once you have verified the sensor is good, then you need to check the connector itself.
When you purchased the new sensor, did you place the old one next to it, and verify that they were identical? The distance the sensor protrudes into the head is critical, if the sensor is not close enough to the tone wheel, the voltage generated will not be high enough for the ECM to see the signal.

 

JEEZ! Now that sucked! Ok really sorry George, I got evacuated because of the stupid fires down here in SoCal, but I am back now! Ok, so the sensor is exactly the same PN as my bad one and it is identical, also, my "bad" sensor has 1.2k Ohm's... so I guess that its not bad.. and something else must be the problem?

I started the car, and pulled the connector off of the camshaft sensor and it has no affect on the engines idle, still sounds bad if I have the connector on or off the sensor. So it sounds like it just goes into a default running mode and doesn't even operate using the input from the camshaft position sensor circuit.

I shot the actual connector going from the sensor (2 pins) and its shooting good with continuity.

 

Yea, I hear the fires are bad, I have a uncle that lives by JPL, not a good thing.

So there are 4 things that can cause this code. 1) sensor 2)wiring 3)starter 4)ECM
You have replaced the sensor, so you can eliminate #1
I do not understand what you mean by "shot the connector"? but I assume that you mean that you ohmed it out. Now I would suggest disconnecting the grd wire on the battery. Then disconnect the connector on the ECM, ohm the pins on the connector. the idea is to ohm out the harness, back to the sensor. (Do not ohm out the ECM itself). Make sure that you ohm across the sensor, and also ohm the wires to grd (very important).

Once you have verified the integrity of the harness, there are two other things to check.

1) remove the valve cover and check the tone ring, ( the ring with 1 tooth, that the camshaft position sensor monitors). The tone ring is what generates the magnetic field that induces a voltage in the camshaft position sensor. Look very closely at the entire circumfence of the ring. Look for any signs of cracks, splits, hairline fractures. Any defects will affect the magnetic field, and that would affect the signal.

2) starter. Now my manuals do not go into any description on this one. But looking at the schematic, I see a signal that goes to the ECM, that tells the ecm when the starter is being energized. I would verifiy that this signal is present when the starter is engaged.

The last possibility is the ECM, but I do not believe that this is your problem. Do you have any friends or relitives that have access to a Oscilloscope? If so, I can send you a jpeg of what the signal should look like. This would give you a what you would need before condemming the ECM

 

Hey George you can send me the pic, I work with Oscilloscopes every day at work! Thanks dude!

 

P0340.pdf

Ok, here is what it should look like.

 

Ok, looks like the sensor isnt a problem, also I checked the camshaft nub that sticks out off the shaft and it looks good. I wired up the connector and I am getting about 25k ohm's resistance continuity, I feel my hand as far back as I can on the harness and move it around and I can see no change in the continuity, now I need to basically find out witch plugs these go to on the ECM to shoot through-line and see if there is any opens, do you have a diagram of the ECM plugs so I can see where these two wires from the sensor go on it George?

 

96ecm.pdf

This is the ECM connector. but first. When you check the tone wheel, you need to look at the entire circumfrance of the sensor, not just the single tooth/nub. Any damage/flaw is to be suspect. This is a reluctance sensor, and is more sensitive to damage than you would suspect.

 

Update*

Sorry I haven't been on much, I actually had to put the Lexus on the side-line for a while to take care of more important things... but, I am back, and need to fix this thing or just scrap it.

So, here is what I have done during our break:

I shot the wiring from the camshaft sensor to the PCM, it all shoots good, nothing is shorted to ground and continuity looks good.

I re-checked the sensor and installed a new one, still definitely not the sensor.

I thoroughly checked the circumference of the cam where it is being sensed, everything looks perfect.

I checked the timing alignment marks, everything seems to be aligned, and I never originally took the timing belt off of the cam when I adjusted the shims so all I should have to worry about are the marks, and everything lines up perfectly..

Now I am not sure what else I can even do other then change the dang PCM...

 

it might be a stupid question, but where are you guys reading these codes?

 

You can just use a regular automotive code reader. You hook it up inside the car to the left of the steering wheel and when you start and run the car it will tell you what made your engine warning light come on.

 

If you have access to a oscilliscope, you could verify the signal at the ECM, it should be app 6 volts PP. You could try measuring the signal with a DVM, set it to AC volts. My quess is that you should see around 2 volts ac.

Otherwise, the only thing left is the ECM. Since you have verified the tone ring, sensor and wires to the ECM, the only componenet left is the ECM. I am sure that this issue is not related to the prior mis-fire on #4, it would have to be just a coincidence.

 

Just changed the ECM for a good one, problem still exists, guess its time to take it to a dang mechanic...

 

Figured i'd update this with the fix. Timing belt hopped a tooth back when I was manually turning it trying to fix the valve problems. Fixed the timing and its good as new!