Check Engine - P0340

[bigA]

Just replaced my camshaft position sensor and the synchronizer because it was squealing pretty bad. Got everything lined up properly (I think) and put it back together. Truck runs fine and no more squeal. But now the second or third time I run it, the check engine light comes on. Pulled the codes and comes up with a P0340. Also came up with a P0100 or P1000, but that seems to be a false reading. Any idea why it only shows up on the 2nd or 3rd start? Does the code get thrown if the sensor isn't lined up properly? I think the sensor must be working because I don't think the truck would even run if it wasn't.

 

[Runnin'OnEmpty]

BigA, the P1000 is "OBD II monitor testing not complete", so you can ignore it for now.

The P0340 is "Camshaft position sensor circuit malfunction". Since it starts and runs OK, I'd unplug and re-plug the sensor, maybe spray it with WE-40, and see if that has any effect. It sounds like the sensor has an intermittant power or ground circuit......?

The OBD II system will set a code if it detects a fault on two consectuive occasions. That's why it takes two (or three) starts to light the MIL.

ROE

 

[MEXEXP]

Had the same

Well almost two months ago, we had the same problem on my father in laws explorer 99 V8, we change the sensor, we changed the distributor or shaft that goes on the cam, had everything lined up, and it threw the code again.

Well we found a friend of a friend who works in a Dealer in El centro, Ca. and the final problem was diagnosed on being a bad alternator, something inside was shorted and it generated negative pulses that were screwing the pulses generated by the cam sensor. we changed it and it runs perfectly.

Hope this helps, it sounds strange but it fixed his explorer.

 

[Turdle]

^^^^Yes I agree, I get that code if My battery is low ^^^^^
However, from experience I can tell you this, the cmp sensor adjustment is critical. You must use a synch alingment tool specific to that year truck. Everything will seem great and all the sudden you have a piston with a hole in the top.( burned)
It was a real pita for me because I ordered the tool 3 times and they and got it wrong each time.
The cmp sensor syncronizes the fuel injectors, and is real critical in 97 and later v-8
I finally was able to locate a ford performance enthusiast-auto tech garage, he loaned the tool to me.

 

[Macgiobuin]

I had the same problem with my '00 Merc mountaineer. P0340 kept coming up, even after replacing the cam sensor, wiring to the PCM, 2dry ign cables, sp plugs, head gaskets, swapped coils, geez... still came up every time I cleared it- it would run for the first trip, with no CEL turned on, then as soon as I started it, CEL is on and it is the P0340, again. Finally, I read on another forum that the problem may be the alternator. I just put a new one in about a month before the problems all started. How to diagnose: Charge up the battery. Clear out the codes. Run it until the P0340 shows. Bring it back home. Clear out the codes. Disconnect the alternator. Yes disconnect the alternator. Isolate the battery terminal at the alternator from any short circuits by wrapping it in elec tape. Take the car on the same trip. If the code does not set on, you found the problem. The voltage regulator is transmitting stray AC voltage that is being picked up by the cam sensor or the PCM and throwing the whole system off. Do the test in daylight with no loads on--no radio, no headlights, no blower. I didn't believe it was possible, but now I am a believer. -Mac

 

[SoNic67]

Thanks guys for your input!
2001, V8 5.0L engine. I had a backfire, shaking engine at over 55mph and the same P0340 code. Instead of changing the sensor (as per code), I checked the alternator voltage - 13.1V running at any RPM.
Replaced the alternator with a "Worldwide Alternator" one (since that 13V voltage is not correct). Now I have 14.5V at idle and CEL turned off by itself!

Looks like the CMP sensor is VERY sensitive to "clean" and proper voltage!

 

[mbruffey]

that 13V voltage is not correct

What is correct Alt output, and where is that spec'd? Thx, LMB

 

[SoNic67]

Alternator voltage at idle rpm, lights on, AC on, should be 14.4-14.5V.
Less is not "just" less volts, it is actually negative voltage pulses superimposed over the DC one. And the sensor is sensitive to that pulses.

 

[Sabe]

Point well made about the "14.4 volts". For those of us who use an the old-time analog volt meter with the swing needle, we'll call it "14 and a half" volts. Anything less than that - there's a problem - usually with the regulator. Remember to zero-out (calibrate) the meter before you touch the terminals.

 

[matt0248]

Most alternators will not output 14.5 volts at idle with all loads on. Also, the charge level reduces at battery temp rises. Most newer vehicles take this into account. YOu should see around 13.5 volts at idle with an engine at operating temp. Also, If all the loads are turned on, the voltage will drop at idle. But it shound not drop below about 13V. it should eventually find a stable voltage and hold there.

 

[mbruffey]

I show around 13 millivolts AC at the battery. Fluctuates by maybe 0.2 mV. Would that be enough to cause a misfire that cannot be traced to any single cylinder? I can hardly believe it would, but why not ask? Anyone else actually tested for AC mV, for sake of comparison? 1997 Explorer 5.0. Thx, Mark

 

[matt0248]

I show around 13 millivolts AC at the battery. Fluctuates by maybe 0.2 mV. Would that be enough to cause a misfire that cannot be traced to any single cylinder? I can hardly believe it would, but why not ask? Anyone else actually tested for AC mV, for sake of comparison? 1997 Explorer 5.0. Thx, Mark

13 mV AC is very small and should not cause a problem.

 

[SoNic67]

My voltage was 13.1V and the CEL was on with this code. I have replaced the alternator with a OEM one and now I have 14.4-14.5V at ANY rpm (including idle). And CEL cleared itself... Code was P0340.
Measuring AC with a meter would not show the whole "story" - let's say it is not calibrated for spikes.

 

[hotstang111]

i actually reset mine a couple hours ago, if you dont get the correct syncronizer alignment tool it will set the code, the tool for the 5.0 and the 4.0 look very similar so ford tech have actually been messing them up to, the ford part number is t95t-12200-a and the global is 303-529, cylinder 1 must be at tdc, slide it in bolt it down and pull the tool off, good luck getting the tool, hard to find i had to borrow one from an asset program

 

[SoNic67]

I did position my syncronizer "by eye"... Tool just makes it easyer to align the center of the hole with the "flag". Dorman tool alignes the middle of the flag with middle of window, but on my V8, the original arrangement was like below (edge of flag aligned with middle of window) and this is how I did reposition the new one:

 

[raygulley]

could my 2000 watt stereo system make this code?

 

[matt0248]

could my 2000 watt stereo system make this code?

anything is possible. The cam sensor signal is very sensitive to electrical noise.

 

[Allen35540]

Radio transmitters and avoiding interference.

For those running radio transmitters such as amateur and CB radio equipment should use high quality coaxial cable and mount the antenna up high, (on top), especially if you are running power. I have not experienced any interference to the system or that sensor in my 95 Eddie Bauer even though I have 200-watts of sideband power coming out the antenna. The antenna mounted on the front luggage rack and then consequently grounded with a good run of high quality coax should be no problem.

 

[brokenarrow]

I just got a P0340 cmp a couple of weeks ago, the truck was running fine for the last 2 wks up until today the engine started running rough. Following this thread i checked the voltage at the battery and the alt. and found that the voltage is hovering around 14.00 to 14.20 and sparaticly jumps down to 13.20 with and without load. Im just trying to find out and be sure it is the alt before i go buy one. I know i probably answered my own question here but i need to be sure.

I made a video with the truck under load and not under load, you can hear how bad the truck is running. Any help would be appreciated. Thanks

 

[brokenarrow]

Gave in bought a new alt and threw it in, cleared the code and took it for a spin, so far no 340, cleared up the rough idle a little but still has a little hiccup. ill give it couple couple cranks on the key later to see if 340 comes back.

Question?
Where is the Cam Position Sensor? Is it that sensor with the 2 wires just above and to the back of the water pump. I have '01 Ex v8 5.0