Im having a problem repairing my 1997 aerostar with a 3.0 engine. Code po340
comes up. Ive replaced the cam sensor, cam sensor housing and the pcm.
Using the diagnostic charts, I've thoroughly checked out the wiring, in the harness, at the sensor, and at the pcm. I've set the cam sensor housing at TDC
with the appropriate timing tool. Code P0340 still comes up. I've seen a couple
of other aerostars with the same problem. Ford TSBs are of no help. Does anyone have any ideas?

 

Hi Werefour146:

Welcome to our FTE forum. Unfortunately, I'm not too well versed with OBD-II systems, but hopefully someone will come along shortly to answer your question.

Regards

 

Welcome!

The P0340 indicates a Camshaft Position Sensor Circuit Malfunction. The keyword here is circuit. The malfunction can be anywhere in the wiring to and from the PCM or the PCM itself. The code can be set if there is a short to ground, short to power or and open circuit. You need to test the whole circuit before replacing parts.

Also, A special service tool such as Syncro Positioning Tool T95T-12200-A must be obtained prior to installation of the replacement CMP sensor. Failure to follow this procedure will result in improper sensor alignment. This will result in the fuel system being out of time with the engine, possibly causing engine damage.

Or you could have purchased a bad sensor off the shelf.

 

how often and any special circustances cause the code? is it setting the CEL?
as long as u are in closed loop operation, i would not worry about it

ever had a serious antifreeze leak or boil over spraying back across the engine? or driven thru deep water or water spray up into engine compartment, salt water especially bad?
suspect corrosion in one of the connectors

i've also read that close routing of sensor wiring to ignition spark plug wire can cause pickup of spark voltage and feeding to PCM disrupting the low level sensor signal...Ford did some rerouting of wiring and harness on some vehicles for this and other sensor problems caused by spark voltage induced into PCM sensor wiring. On some, Ford had to replace with special shielded harness and individual sensor feeds

 

Thank you for your info. I've checked all the wiring and I'm suspecting that the spark
voltage is interfering with the sensor output. My next step is to get a new harness
from Ford. I've triple checked the camshaft sensor, pcm, the cmp sensor housing
and the synchronization with the special tool that is required.

 

Before buying a new wire harness, I would call up Ford and ask if there is a recall on the wiring harness. I know in that era of Contour/Mystique did/do have a recall, but usually the wires are rusted and the insulation is frayed.

 

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

 

Follow up on an old thread related to DTC code P0340:

My 97' 3.0L Aero is setting this code. It uses two times starting the engine only to get the CEL back, right after erasing the code. There is a 10-steps Pin-Point test on alldatadiy which i've performed today. Steps 1 to 6 have passed with no problems. Step 7 has failed:

DR7 - Check CMP for short to GND

• Key off
• Breakout box installed, PCM disconnected
• CMP sensor disconnected
• Disconnect Scan Tool from DLC
• Measure resistance between Test Pin 85 (CMP) and Test Pin 51, 103 (PWR GND) and 91 (SIG RTN)
• Is each resistance greater than 10K ohms?

The Digital Multi-Meter shows no ohms (circuit open) here on both connections. My question: It's in my understanding, that a open circuit (no connection/short at all) should be the desired value for this Test. Or am i missing something, perhaps a 10K ohms resistor in this particular circuit that can break?

note: i have no Breakout box, the Pins from my DMM do fit into the PCM Harness Connector connections. Test Steps 8 and 9 cannot be performed without a Breakout box because the PCM is involved in these Test Steps.

Thanks


97' XLT RWD 3.0L Vulcan 117180miles

 

Yes, your meter is looking into a high >10k ohms, circuit, actually solid state devices in the cam PS>. anything less than 10k ohms is Fords cutoff point indicating damaged failed components.

you may have corroded connector pins on the cam PS wiring connector, the CPS itself or the PCM connector pins. too common and causes all sorts of false readings and problems in high impedance extremely low signal current/voltage circuits.

you can do steps 8 and 9 without the BO box by plugging back in the PCM and unplugging the cam PS and reading for #8 & 9 from the cam PS connector. done it on Ranger, lots more room than an Aero under the dash hole

use silicone dielectric grease on all connector pins after checking for corrosion and pin damage on final assembly.

I has this same code years ago, had to reposition the cam PS wiring circuit and move it away from the plug wires plus wrap household aluminum cooking foil around it. plug wire to cam PS cable spacing is critical for high voltage interference.

usually when the cam PS fails itself, engine will not start, no injector fuel pulses

 

Okay, thanks a lot for your reply 96_4wdr! Further investigation ahead.. i've noticed moisture build-up inside the PCM connector slot. Minus degrees since months where i life plus high humidity in my garage. Lot of stress on material and humans as well.
WB

 

Hello Community

My DMM interprets 10K ohms as open circuit - whereas the analog multi-meter from my Grandfather shows it correctly (Simpson 260 markII)
Took the aero for a test-ride with the doghouse open. At acceleration, around 3000rpm there's a rattling noise coming from rear of the engine. Dismantling the CPS reveals the culprit which causes the P0340:

Magnet broke off of the sensor


Debris everywhere inside


Egg-shaped vane


Thinking of reshape the vane but there is maybe fine debris/dust left between the vanes rod and the camshaft-synchronizers casing even after a clean out with air. New synchronizer or one from the yard protects from major problems like a stuck rod that blows the engine.

Funny, 97' Vulcan Engine runs even without the CPS. PCM is having an alternativ source to determine the timing with P0340 set.

Camshaft Movie

 

 

lots of guys install the complete unit without using the special tool

read the descriptions at end of this thread
Ford 3.0L Camshaft Position Sensor

 

 

Yeah, new Motorcraft Camshaft Synchronizer* & Sensor underway from Rock. Takes 5-7 days approx from US-Warehouse to Germany. Until then i'll get theoretically familiar with the changeout procedure.

thanks again

note: i'm going with the CMS Motorcraft part #DA2094 to replace my original part #F58E-12131-AB. Will leave a notice here when it's the wrong part. Otherwise it's the right.