[jondickson]

Hello Allpar community! I'm new to the site. I have an issue that I hope you guys can help with . I have a 2002 Chrysler PT Cruiser that keeps giving me the code P0340, which is a bad cam shaft sensor. I have put 3 different ones on still the same outcome. I've done several other things to make sure all is good. The PCM is new, Fuel pressure is perfect, complete tune, checked timing, (it has a new timing belt and pulley) new crank sensor, new cam magnet, checked all wiring, and several other things. Here is where it gets interesting. The car will start, but it takes about 5 to 7 seconds of cranking. When it starts it of course give the code, but drives great. After you drive the car or let it warm up for about 10 minutes it shuts down. The car will then start perfectly. You can clear the code and it will not come back until the car cools down completely. I did this the other day. Drove the car, it shut down, cleared the code,,,, drove it the rest of the day stop and go, off and on for about 200 miles.. Plenty of power the whole way. When I got done for the day,, I turned it off for about 2 hours,, it started all over again. I did some test here and there. The main one that I did was get it to operating temp, and clear the code, then I immediately took the cam sensor off and put it in the freezer for 10 minutes. Put it back on, everything starts back over. So to me the cam sensor has to get warmed up before it works. This is consistent with other cam sensors. I'm lost and don't want to take it to the dealer and spend 500+ dollars and still not have it running. I basically want to get the car correct so I can sell it, just bought a new 200. Id hate to have to explain this to someone interested, and I definitely couldn't get what I could out of it if it was doing this. Please help. Thanks guys! :excited:

 

[chuzz]

Where are you purchasing your sensors? If they're aftermarket, that may be the problem. I'd suggest OEM style sensor from a Mopar dealership. Also, they come with a paper spacer on them (or they should). This is not to be removed before installation. Are you removing it? If so, that could be the problem. That is to provide the proper clearance for you. If not that, then I don't know what to suggest. Congrats on the new 200 BTW. I got one back in April and love it. Already got 8,500 miles on it.

 

[jondickson]

Hey, thanks for the reply. I purchased one from autozone and another from orielys. I also had 2 OEM, but they wasn't new. I do know they worked on the other motors though. I haven't see a paper spacer, just the green gasket. I've used aftermarkets before on another pt. I'm willing to pay the difference for OEM if I knew it would work. It sounds like it could be the problem though. Another thing I tried was I removed the magnet, and put a few small washers in behind it to bring the magnet closer to the sensor. It still did the same thing, but took less time to kill the motor, or warm the cam sensor up. I know its in the cam sensor, so I guess ill take your advice and buy the oem sensor. I appreciate the help..... And yes the 200 is great. Not to put down the PT, but definitely an upgrade for me. I drove a new Dart as well. Not bad there either. A little rougher ride, but sporty. I wanted the Dart for the MPG, but they give me a better deal on the 200. My plan is to keep her for about a year, then trade it in on a new Challenger. At least that's the plan, we'll see! Thanks again, and if you have any other ideas let me know! :cheers: :thumbsup:

 

[jondickson]

I got a oem cam sensor today for 90 bucks, hope tht works

 

[dana44]

It should work. I had an almost similar situation with misfires, of which two years later and final trip to the dealership, $800 when all was said and done (smog was in there, had to have the belt timing checked, then diagnostics costs, and the cam sensor itself). It is shutting off because it is counting "false" "misfires" from the material it is made out of for some reason, but not really being an issue, just static or something due to some trace element in the casing of the sensor itself.

 

[jondickson]

Ok, thanks for the info! I sure hope this works. I think its weird that as long as its hot it works. When i put it in freezer and it acted up i was very puzzled.

 

[dana44]

The aftermarket cases have something in them that the electronics just don't like. Not sure what it is, but I stumped the electronics specialist at the local Chrysler dealer, and that was three years ago, not a problem since with OEM sensor.

 

[jondickson]

Good deal! Crazy its like that,,, i get off work at 2 in the morn. Gonna put it on first thing when i get home! Ill keep u informed.... Thanks

 

[ImperialCrown]

There was a cam sensor connector terminal change from pin-style to blade-style terminals. I rememer that a new pigtail had to be spliced into the harness when the new cam sensor was changed. I think that the blade-style offered less chance of 'intermittent' contact. I don't know if this applies to your vehicle. 11 years of engine vibration may have spread the terminal contacts slightly. Gently pinch them to offer a tight metal-to-metal connection.

P0340-NO CAM SIGNAL AT PCM
When Monitored: Engine cranking/running.
Set Condition: At least 5 seconds or 2.5 engine revolutions have elapsed with crankshaft
position sensor signals present but no camshaft position sensor signal.

POSSIBLE CAUSES
INTERMITTENT CRANKSHAFT POSITION SENSOR SIGNAL
INTERMITTENT CAMSHAFT POSITION SENSOR SIGNAL
INTERMITTENT WIRING
INTERMITTENT CONDITION
8 VOLT SUPPLY CIRCUIT SHORTED TO GROUND
8 VOLT SUPPLY CIRCUIT OPEN
8 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
CAMSHAFT POSITION SENSOR SIGNAL CIRCUIT SHORTED GROUND
CAMSHAFT POSITION SENSOR SIGNAL CIRCUIT OPEN
CAMSHAFT POSITION SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE
CAMSHAFT POSITION SENSOR SIGNAL SHORTED TO 8 VOLT SUPPLY CIRCUIT
SENSOR GROUND CIRCUIT OPEN
PCM - 8 VOLT SUPPLY
PCM - CAMSHAFT POSITION SENSOR SIGNAL
CAMSHAFT POSITION SENSOR

 

[jondickson]

Well I got a brand new OEM sensor, and I also purchased a new connecting wire. Installed both, nothing changed. :runaway: Still the same crank crank crank, then starts.

 

[ImperialCrown]

Rule out the 'Possible Causes' list one-by-one and you should find your answer. Let's rule out the sensor itself and the PCM and do some more diagnosis. Do you have access to a good scan tool that can display the cam/crank sensor readings?
A car can start like this when the cam sensor isn't supplying a signal. The crank sensor can't tell the PCM where #1 TDC is (that's the cam sensor's job), but it will eventually find itself and start after several revolutions of cranking by estimating cam position.
The cam sensor only watches the intake cam, the exhaust cam has no position sensor.
Is it still throwing the P0340 code?
This sensor shares the 8 volt supply with the crank sensor and I have seen crank sensors cause a cam sensor code because of pulling the 8v supply voltage down. The grounds at the PCM must be clean and secure. The wiring harness must not be pinched or rubbed-through anywhere between the sensors and PCM in the engine compartment. Watch for where the harness may rest against any sharp edges and have worn through the wrapping tape or wire insulation.
Has a scan tool been plugged in to watch cam and crank sensor signals while running? Some simply indicate whether the signal is 'present' or 'lost'. You want to see a solid 'present' for both.
A tooth off on a cam belt can cause the cam sensor signal to be 'lost' if it falls outside the expected window and a good scan tool can show the cam/crank relationship angle in degrees. If it is off more than a few degrees, it will cause starting and fault code problems.
There is a cam/crank 'relearn' feature in the better scan tools (i.e.-DRB III or equivalent). I don't think that it could generate a P0340 fault though. It is an adaptable memory used to compensate for belt stretch. The relearn won't take the place of incorrect belt timing.
These marks can be very difficult to line up due to not being able to view them straight-on. You will need a small mirror and a straight-edge across the cam bolt centers to verify correct timing mark alignment on a PT.
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[dana44]

Have you also disconnected the battery to reset the computer? Takes about 15 minutes of disconnect to return to factory pre-sets.

 

[jondickson]

Hey guys, thanks for the replys..... Ive disconnected the battery several times, sometimes overnight. Still the same. I own a scan tool but its mainly a code reader. Its an actron. If it reads both sensors i dont how to do it, but i dont think it does. Ive put 2 other crank sensors on prior to this last cam sensor.

 

[ImperialCrown]

What model Actron? Many times the instruction manuals are on the website.
If it can read cam/crank sensor status, it may be the only diagnostic tool you need.
A voltmeter can check for a good uninterrupted 8 volt supply and good low grounds. Driving with it underneath a wiper blade with long leads until the fault occurs can show you how the voltage supply is doing.
If the Actron is capable, writing down the 'freeze-frame' or 'snapshot' or 'starts since set' information stored along with the fault code might help in finding out a root cause. This information is basically what everything else 'engine-wise' was doing when the fault was tripped.

 

[dana44]

OK, so if the cam sensor is now a factory original replacement and the crank sensor has also been changed, resetting the computer by disconnecting the battery has been done several times, I think these three things can be ruled out. You changed the cam magnet, is it possible it isn't installed correctly, or is offset some way that it is reading or signalling improperly? The belt being changed could possibly be off a tooth, as noted, the extra cranking is re-evaluating and finding number 1 cylinder using the cam or the crank sensor because one isn't able to identify both at the same time (to speed up the starting/injecting sequence), and then the tmep sensor or air intake temp sensor used (not sure how this is part of the sequence, but, temp sensors are part of the running sequence of the computer fuel tables), and quite a few years back I had a friend that was having cold starting problems and running because of a temp sensor that wasn't working so the engine had no power whatsoever and could not be driven until the engine warmed up and this sensor was basically removed from the engine running sequence.

IC, is this a possibility? An input (electronic sensor) for the start sequence not be working? Once the engine is warm isn't needed anymore for input?

 

[ImperialCrown]

If the Actron can read sensors or inputs/outputs, let's make sure that the sensor readings make sense.
Before a cold start with the key in ign-on, the engine coolant temperature (ECT), battery/intake air temp and ambient temp sensors should all read within a couple of degrees of each-other.
The barometric sensor (BARO) should read the prevailing air pressure. The MAP may read zero with the engine not running.
The RPM (crank sensor) should read zero. Cam/crank sensors should read 'lost' or 'not present' until cranking, then they should both read present.
Write everything down and let's see if anything looks out of place.
I think that if P0340 is the only code being set, then we have to look at the cam/crank sensor circuit first. Basically it is the 8 volts in, the signal out and the good ground to the internal PCM ground filtering to a good, clean body/neg.battery post ground.
A bad (leaky) fuel pump check valve may also contribute to a first hard start of the day if the fuel is draining out of the rail and lines and back into the tank after sitting awhile.

 

[jondickson]

Its a cp9575 actron. I know it has a section tht reads what the motor is doing. It all looks good. Ive remove alot of the wire covering throughout the motor . Cant see nothing. I did notice the water temp guage is also the same ground in the sequence of the cam sensor. Maybe ill unhook that and see. The only thing that baffles me is warming it up, then cooling the cam sensor off in the fridge. Leads me to believe something to do with magnet area, but it was the same before the new magnet.

 

[jondickson]

If it was a shorted wire shouldnt it do it all the time, or would warming it up cure it?

 

[dana44]

Warmed up may cure it, especially if noted as a sensor which was needed during cold/warm-up input, which is an indicator of the dying at the ten or so minute mark, and then running fine after, whether or not the check engine light is on. It falls into the open loop and closed loop operation, an input making (or lack thereof) the shutdown, and then the inputs are different because the temp is different, remaining above that temp goes into different run programs (open loop/closed loop thing), and all is fine. ImperialCrown listed what should be indicated not running as a start, have to go from there.

 

[jondickson]

Makes sense. Im gonna do what i can to this thing. Thanks guys, ill keep you updated