gzaid1

I recently had my alternator go bad and whenever I'd run my A/C for a long period of time (i.e., 1 hour or more), my charging system was getting low. Long story short, I changed my alternator with another 100-amp one and my A/C and charging are just fine now.

I also went ahead and changed both distributor caps & rotors with "O.E.M." dealer-parts from the local Lexus dealership.

Now, my Check Engine light has turned on and it's Code # (P0340) -- DTC P0340: Camshaft Position (CMP) Sensor CKT Malfunction.

I purchased a NEW Camshaft Position Sensor #1 (Bank #1 - Driver's side) & installed it, and the Check Engine light returned with the same exact code - P0340 (Camshaft Position Sensor #1 Malfunction).

I checked the actual "connections" on the Camshaft Sensor and all the wiring seems to be perfectly normal & fine.

The "symptoms" of the car are as follows:

At idle in park after the car warms up and the idle drops to between 650-700, the idle has a little "play" in it and it moves up and down a bit. It's not surging badly or anything, but the idle is not smooth. Also, if you're in drive and stopped at a light with your foot on the brake, the idle does the exact same thing. When driving and moving down the road, the acceleration feels normally smooth and without hesitation. It's just at a complete stop or idling in park or neutral, it does this...?

Any suggestions or ideas as to what can cause this? Could it be that when the initial alternator was going bad (with the A/C running) that it possibly "shorted-out" a section of the computer or ECM and it's not correctly reading this signal?

Thanks a lot in advance for any help you can provide or suggest to me.

Och

iTrader: (3)

Well start by swapping the new sensor to the other side i guess.

Its beyond me why there are even two sensors in there, they should've only put a sensor on one of the cams.

gzaid1

The other side (passenger side) Camshaft Position Sensor is showing to have a different part # than the Driver Side (Bank #1)...??

Will swapping it still be worth the time since the Scanner is showing the malfunction code to be on Bank #1 ?

3UZFTE

I know what your saying, but the reason why is because it is actually operating two separate ignition systems at any given time. Which is why there are 2 of everything. I would clearly do what Och said, try another sensor in there. Also check the wiring going to the sensor as it often becomes cracked, pinched, cut, whatever you may have, just check the wiring.

gzaid1

I will check the wiring and connectors on both ends of the sensor this evening.

Thanks for all your help guys.

Will have an update hopefully by tomorrow.

Och

iTrader: (3)

Good luck, and let us know what happens. Double check your distributor assembly, make sure that everything is assembled as intended.

Och

iTrader: (3)

That is a good point. I know that 3UZ only has 1 cam sensor on drivers side.

gzaid1

I took the vehicle to probably the best auto electrical guy in town who's got about 30 years of experience under his belt, and he's pin-pointed the problem as being a TIMING PROBLEM. It seems as if the timing is just "off" - with regards to the sprocket which is at the end of the camshaft -- and this is giving the Camshaft position sensor an INcorrect reading, thus triggering the P0340 Malfunction light.

The car's timing is getting checked today and I will post an update as soon as it is available.

jhill20

iTrader: (1)

gzaid1, Just for kicks, make sure they have checked to see that you didn't "clock" the rotor incorrectly. I have not worked on one in a while, and honestly don't remember what the shaft looks like but, there are quite a few distributor shafts that aren't indexed, in other words you can only put the rotor on one way, and are very easy to put on incorrectly which can cause odd driveability issues and will set a specific cam ckt code.

I'm sure they've checked this in their diag, but just in case, thought i'd chime in.

Hope this helps...

rx7guy

If you want to double check your rotor settings, check out the pics in:
https://www.clublexus.com/forums/ls4...-question.html

Also, any chance you knocked off a hose that's causing a leak in vacuum? I'm thinking the idle air control hose on the throttle body hose(there's two of them). One is connected via plastic which breaks a lot and another that's metal.

Och

iTrader: (3)

Could the rotor be 180 degrees off?

tsarang

I am also getting the dreaded P0340 code. My car (96-ls400) would start and then the RPMS would go to 2000 then 1000 back and forth several times and after few secounds it will die. same thing when I restart.

If i give throttle the engine will not die but The car shudders and the rpms still keep on going up and down.


a) traced wires for shorts. They checked out ok.
b) Tested resistances for both camshaft sensors and the crankshaft sensor, all came out to be within the right specs.
c) tested ignition coil resistances, came out to be within the right specs.

Do you thing my timing is off. My car was running perfectly, It only started with the below 20F tempratures we are getting in Florida.

Help definately needed from the gurus out there

Please Help

jhill20

iTrader: (1)

ok, so, not at all saying that this could be the cause of the CMP ckt code but you may want to check the operation of the IAC, with regards to the cold temps...

Although I'd have to say that you're timing is probably off....kinda of interesting why the cold weather is affecting it so much though. Wondering if it is a separate problem entirely.

Did you ever get the timing "officially" checked?

mazu072

I have 2006 IS250 and exact same problems....

I bought and replace the cps but it still came out (normally the error signal on and off : engine, check vsc,traction )off)

How you fix it?

brybo86

When I did the timing belt on my 1996 ls400 I put the distributor rotors in backwards.
Car did not start at all, obviously.

There was no check engine light or codes thrown, I checked.

This is not your problem.