I have a 2001 F150 v8 4.6L pickup. About every two hundred miles or so it will act like it's not in gear. Speeds will drop while you are driving and RPMs stay up or go higher, Service Engine Soon light come on, overdive light on the steering column come on. Also sometimes when stopped it will idle pretty high. Now it has done this a couple of times, to fix the problem I put it in neutral while driving reved the engine some and pulled it back in drive. And sometimes it might take once or twice to fix it. Now we have replaced the throttle positioning sensor. Yes we did get the codes off of it and they are as follows: P0113 intake air temperature circuit high, P0123 Throttle/pedal position sensor/switch "a" circuit high input, P0340 camshaft position sensorcircuit malfunction, P0453 Evaporative Emission Control system pressure sensor high input, P0708 transmission range sensor circuit high input, P1289 cylinder head temperature (CHT) sensor circuit low input. Lucky me my warrenty just went out at 65,000 miles, and the truck has 66,200 miles, now I feel stuck, and which road should I take to fixing this problem. Any help would be appreciated, talked to the ford dealerships down here and the are overbooked and outrageous with their prices for minor things, I can't imagine major ones. So any help in diagnosing this problem would be greatly appreciated.

Thanks.

 

I'm no expert. Just an amateur who's read this thread and others for 2+ years. I've never seen a post with so many DT codes listed. If it were me, I'd suspect the PCM (powertrain control module) or its harness. Get a Chilton's or other manual. Locate the PCM and check its wire harness for damage. The PCM itself is an $expensive$ part so I would not replace it before ruling out everything else.

If PCM and harness pass the visual inspection test, I'd have the "tranny" checked. Are there AAMCO shops in LA? In my area (suburban NYC) they offer electronic transmission diagnosis for under 50 bucks. Post their diagnosis here and others may tell you if it makes sense.

Next I would check all the other sensors on your list and their wireing harnesses.

Good Luck,
wmc

 

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if the motor speed goes up and the truck slows down, then the torque converter is slipping, meanign running low on fluid. i would drop the transmission pan, clean the crud, change filter and oil. --- you might just check the oil level first to see it is o.k.--- i think the engine codes may be the effect of the transmission slipping and motor revving up-- the motor/ computer are overheating and "lost" about what is happening.

 

The oil has just been changed in the truck, so oil levels are all good. Also we have changed the radiator fluid and hoses, all good there. We were talking about getting the trans system cleaned though. We figure it is one problem though setting off all these other sensors. What about the camshaft sensor(s?)? Also someone has told us about the voltage regulator? We will be changing the fuel and air filter today, not that, that makes a bit of difference, what about the sensor that's in or around the air filter (mas?)? Now this problem doesn't occur but like I said close to 200 miles. Ck'd the trans fluid, both cold and while running and it isn't low. Any more suggestions would be greatly appreciated.

 

The PCM won't make the tranny kick out of gear. If it quits pulling, then you have internal tranny problems. The PCM controls shifting and converter lock-up, but it still manually engages with the shifter linkage.

 

The P0708 is a good clue.
A bad TRS (Transmission Range Sensor) can cause the transmission to downshift when it's not supposed to. You can be cruising along in OD and it may shift into second gear. If that happens the engine will rev up and it almost feels like you're in neutral.

 

I agree with Racerguy.I am a tansmission tech and I have seen this (MLPS) be the problem.The trans down shifts and no engine braking and you have to rev engine to catch back up.Dont know about other codes.