Hi Guys,

New member here.

Wondering if I could get any help from some fellow enthusiasts. I recently acquired my dad's old truck. Its a 2002 Explorer EB 4.6L 4x4. Great truck, family owned since new.

Recently it has had the service engine soon like pop up and its throwing code P0340. The mysterious cam sensor code.

May I ad that the sensor itself is new, OEM ford. I have just replaced the alternator (which is usually a common problem for this code), and still no luck.

The car starts up, still runs great, and has had no hesitation or stalling.

My mechanic friend checked it out and said that it is getting some voltage, but not as much as it should? the wiring to the PCM looked good too.

The Ohms on the CMP checked out good too.

I'm running out of ideas, and I really hope its not the PCM on this car. I may have to just take it into the ford dealer to see if they can diagnose the car. I do work as a tech at a small indy shop, but currently dont have the time since i'm trying to finish my schooling this year.

I just want my car to be in tip-top shape...

Any comments, or guidance will be greatly appreciated.

Thanks in advance

-Rod

 

Welcome to the forum! Another "-Rod" here.

Per the P0340 troubleshooting steps from the factory service manual, the VPWR to the CMP needs to be at least 10.5 volts between the sensor and the battery negative. Do you know what value your friend measured? There should also be less than 5 ohms of resistance between the sensor ground and battery ground.

-Rod

 

to bump this thread,

first of all. Thanks shorod for all the tips.

My truck has had some work done to it recently - timing chains, tensioners, guides, waterpump, valve cover gaskets, etc. However, I am still getting the P0340 code right away.

I have done 2 checks recently.

Voltage check to the sensor and wiring is very low. 0.5V, or even less.

Alternator is new, but I used a snap-on advantage tool to rule out any bad diodes in the alternator.

New pigtails for the CMP, and Alternator.

I am leaning towards an actual PCM issue.

Any records of how to fix this issue (can it be fixed with some soldering on the board?), anyone rebuilds them? should I just grab another used unit?

I have heard these might need to be reprogrammed? I have a friend with an exact model car as mine and im tempted to just swap PCMs to see the outcome.

Any comments and suggestions would be great. I would really like to get my truck back to be code free

 

I would not recommend replacing the PCM with a used unit. Lots of unknowns when you do that. Go to Autozone and order a rebuild through them from Cardone in Philadelphia. Cardone rebuilds PCMs better than factory new and the price is very reasonable.

Web site - New, Remanufactured Auto Parts Leader | CARDONE

My 94 Explorer PCM cost about $194, about half that cost was core charge. Great deal as far as I am concerned.

 

Thanks for the suggestion explorerjwd. I'll keep it in mind.

my question is more asking regarding programming for these PCM's. Could I use my friends PCM from a same year/model explorer to try it out assuming the part #'s are the same?

 

Does your 2002 have a transponder ignition key? If so, the PATS system is supposedly matched to your PCM. The PCM will be programmed with the original vehicle's VIN and if the VIN doesn't match between the PCM and PATS, the PATS system will not allow the truck to start.

-Rod

 

time to bring this subject back again, as I am still working on it.

I was driving my Ex for the time being with the CEL on with no real issues, but insurance is going to be over in June and it will need emission testing (OBD II Scan). Time to figure this out.

I had the car looked over before.

-CMP is new, ohms within spec
-New CMP pigtail, checked resistance in wiring from the PCM to the pigtail and it checks out for no breaks.
-Timing chain, tensioners, guides, etc have been replaced. Timed correctly.
-Cylinder head temp sensor is getting the 5V power, but the CMP is not (tied in circuit?), so I had an electrician assume that the sense in the PCM is not good and I should look at getting another one.

got a used working pcm unit the other day, time to install it, get it programmed and see if this will solve my problems! Will be updating...

 

According to the manual and information posted in post number 2 above, you are not looking for 5V on the dark green wire at the CMP sensor, but rather something 10.5V or higher. Regardless, it sounds like you're not getting that. I would have suggested confirming a good ground first, then backprobing pin 53 at connector 175c (PCM) before condemning the PCM.

-Rod

 

the problem still persists, another pcm, reprogramming, and still the same error/code immediately shows up

i basically have two other things in mind
-crankshaft position sensor
-grounds

SHOROD: The Power/green wire on my CMP is getting like 0.2V if not that. I checked the resistance from the PCM (53) to the sensor, and it checks out for no shortage. Where do you recommend for checking the grounds?

 

You didn't happen to check for low resistance between the power wire and ground, did you? Maybe there is a short from power to ground, dragging the CMP power low.

If you send me a Private Message with the request and an e-mail address, I can send you a PDF of the troubleshooting guide for this diagnostic code.

-Rod

 

so i am here to post some updates, which have really gone no where since the problem still persists.

first, i would like to thank shorod for sending me the wiring diagrams and troubleshooting guide. they were a big help.

so again, what is new:
-Timing chain, guides, tensioners, crank gear
-Camshaft position sensor
-alternator
-alternator pigtail
-camshaft position sensor pigtail
-used, working PCM (programmed)
-crankshaft position sensor (just done today)

so I replaced the crank sensor today just for the hell of it. it was cheap, so oh well. When i took the old one the resistance was 370 ohms, and the new one was 330ish ohms. Fairly close, so i was skeptical if this was the problems. Well i put the new one in anyways, and it was ofcourse not the problem.

I had my friend, a very knowledgeable mechanic/electrician look at the car first, and then he gave me a hand today for 4 hours. PCM power wiring is 5ohms resistance, ground is good. Even then we ran a new wire to the cam sensor, and a new ground. No difference. We went through everything with a snap-on vantage tool looking at the current waves for the cam sensor, and ignition coils. Apparently bad ignition coils can cause a disruption. We swapped out any coils with good used ones (from a mustang) if we saw any flaw. Then we did a compression check on one cylinder on each bank to make sure timing was correct, if not, it could differ 20psi or more. Both cylinder opposite of each other were 175psi. Spark plugs are fairly new might I ad. Then we started looking at the pcm connectors, making sure they are tight and snug, no real problems there.

here is some more info: if you run the car, erase the codes, start up and rev past 2000-2500 rpm, the codes are not present. We went through the troubleshooting guide for if the codes are not present over 1500rpm (see Z1 trouble shooting procedure).

Current codes are showing: P0320, P0340. Basically they both pop up now within 10 seconds or so. Pretty lost here...

Thinking of looking at 2 minor things though:
1) "the harness issue" which apparently is a problem on the 4.6 wiring harness as it can split the wire going to the crankshaft sensor. A little odd considering the car starts, runs pretty well, etc.
2) opening up the driver side valve cover to inspect timing again, and see how the condition of the sprocket it. Last I remember I didn't see any issues.

I am truly stumped...

 

so after reviewing the cmp wiring diagrams again, is it possible for the heated circuit of the o2 sensor to have failed and then causing low power to the cmp?



i'm going to check for an open circuit possible tomorrow, and I have new sensors on the way.

 

Did the new 02 sensors solve your cmp code issue? I have a similar issue with my 03 EB Explorer, 4.6L, which I have not been able to solve. Alternator, battery, camshaft sensor and pigtail and wiring, crankshaft sensor, and pcm all replaced yet still generating code p0340.

 

im having the same problem also wondering if a clogged cat would cause back up to causing everything to compensate for the vct and cam sensor codes?? i had both replaced already it all started with a misfire in cylinder 6 but ran it with the misfire for a while then truck just went hay wire n would barely run and got a bunch of codes replaced all the coils n plugs cam sensor vct both sides cam sensors on both sides n that was all from ford n still have a problem with the p0340 code coming back only if i drive the vehicle for like 3 miles.... n then runs rough barely runs.. shut it off for a day start it up n runs fine for like 3 miles.... so if u figure out whats wrong let me know ill try it also... 4.6 mountaineer

 

nope. didn't fix, and im honestly lost.

I pulled the valve cover off again, and noticed that at TDC the driver side camshaft sprocket CMP mark is lined up with the CMP sensor, but its not directly in the middle, more to one side. Technically you cant have "1/2 a tooth off". Im pretty sure the car is timing properly. Does anyknow know if this could be a potential problem? does ford tsb's require the CMP to be exactly in the middle of the mark on the sprocket?