Hey all,

My truck recently started shifting oddly. It takes off normally, but it upshifts way too quickly, it seems like it shifts from 1st directly to 3rd/OD. Once this happens the engine will lug severely (like trying to take off in high gear with a stick shift) and it will shift back and forth between 3rd/4th. Putting the pedal to the floor doesn't affect it and the truck barely moves until I either get up to speed or downshift it manually. It used to only do it occasionally, but it's been doing it more and more often and now it's pretty much all the time.

The truck still drives great, I just have to 1-2-D-OD on shift it manually each time I take off, which gets annoying after a while.

The fluid level is OK and I changed the fluid less than 5k miles ago. Does anybody have any idea what could be causing this or how I could fix it? Could it be the computer? No check engine light or anything comes on.

Thanks in advance

 

Sounds like the computer doesn't know how fast the truck is moving, or if its moving.

Run the self test, the KOEO test and see if anything comes up, no light on doesn't mean it won't have a code or two.

Could be the VSS (rear end) or the PSOM (behind the speedo).

Could be a bad connection at the solenoid pack, could be a broken/burnt/pinched wire.

The KOEO test may lead you to the problem, start with that.

Just In case your not sure how to run the test/s here is a link,

Ford Fuel Injection How To Run a Self-Test

 

Thanks for the info on running that self test, I didn't even know that was possible. Turns out the reason my check engine light didn't come on was that it doesn't work at all . Had to read all the codes with my multimeter.

Anyway, here's the codes I *think* it showed. I tried it several times but the quiet beeps on my multimeter were hard to count so I could be wrong about any of them:

66 - TOT sensor output was less than Self-Test minimum value of 0.15 volts.
61 - ECT sensor is less than the Self-Test minimum of 0.2 volts.
14 - Two or more successive erratic Profile Ignition Pickup (PIP) pulses occurred, resulting in a possible engine miss or stall.
633 - 4WD switch is closed
116 - ECT out of self test range 0.3 to 3.7 volts.
636 - TOT sensor voltage out of self test range.
627 - Converter clutch solenoid circuit failure (E4OD)
122 - TPS circuit below minimum 0.6 volts.
637 - TOT sensor circuit above maximum voltage

From your experience, could any of those be causing it?

Thanks in advance

 

Thanks for the info on running that self test, I didn't even know that was possible. Turns out the reason my check engine light didn't come on was that it doesn't work at all . Had to read all the codes with my multimeter.

Anyway, here's the codes I *think* it showed. I tried it several times but the quiet beeps on my multimeter were hard to count so I could be wrong about any of them:

--EDIT: list updated in below post--

From your experience, could any of those be causing it?

Thanks in advance!

 

codes are either 2 or 3 numbers, not both.

 

Yea you have to read them again, but based on what you've posted I'd have to say you have a voltage problem someplace.

Bad connection or connections, Might be a good idea to unplugging the PCM connector and check for any corrosion just to eliminate that as the problem.

All codes you posted are for erratic, low or out of range voltage, and circuit failures, a wide variety of em at that.
TOT above normal would be from it shifting to fast, the tranny fluid is getting to hot because of it. One problem is creating others, domino effect, find the real issue, correct the rest.

Be sure and disconnect the battery before unplugging the PCM's connector.

Make sure you retrieve all codes first, disconnecting the battery will clear all codes and you'll have to start from scratch. Just to be on the safe side, only take a few minutes to check that out, anyway that's where I'd start and work out from there if it looked good.

 

OK, thanks quicklook2 and danr1. I didn't know they were all the same, that makes it much easier to read! I reread them and found these codes:

633 - 4WD switch is closed
116 - ECT out of self test range 0.3 to 3.7 volts.
636 - TOT sensor voltage out of self test range.
114 - ACT out of self test range 0.3 to 3.7 volts.
121 - Closed throttle TPS voltage higher or lower than expected.
637 - TOT sensor circuit above maximum voltage
638 - TOT sensor circuit below minimum voltage

I have some electrical cleaning solvent with a fiberglass brush, I'm going to take the PCM connector off and clean it thoroughly. I'll let you know how it goes.

Thanks again

 

Don't clean it unless it looks like it needs it, if it does be very careful and only clean any pins that look to need it. Don't bend any of them or worse snap any off doing so.

Then apply a reasonable amount of dielectric grease to the connector side before plugging it back in, getting the grease over the pin holes so the pins get covered as you put the connector back on.
Apply dielectric grease on any/all connections you check out.

 

I noticed most the sensors you list have something in common, the are all interconnected via a GRY/RED wire. Your non working self test port is included in that.

"633 - 4WD switch is closed" would be the only one not included in that.

It could be a burnt out bulb and your hung up in 4 wheel and don't know it. Try spinning the front drive shaft, it should spin if in 2 wheel and the hubs are unlocked.

If it won't spin you're driving around in 4 wheel engaged or part way engaged.

 

Wow, outstanding diagnosis. Lateral thinking?

 

Thanks for the advice danr1, I disconnected the batter and took the PCM connector off. It all looked clean and not corroded. I greased it and put it back on and reconnected the battery. Drove it around the block, shifting issue is still present, in the drive around the block it stored only 2 codes:

636 - TOT sensor voltage out of self test range.
638 - TOT sensor circuit below minimum voltage

I'll look for that grey/red wire you're describing.

As far as the 4x4, it's definitely in two wheel, however the 4X4 LOW RANGE light on the dashboard blinks on and off as I drive whether or not it's in 4x4 or 4x4 low range, I think it's an electrical issue (if anyone has any ideas on how to fix THAT would be helpful too).

Could a bad TOT sensor cause these problems? Is that on the same grey/red wire?

Thanks again

 

Thanks!

And well yea I guess, was trying to give him something more other then just "a bad connection" to go on! Maybe narrow it down just a little, these trucks can be, or are, a wiring nightmare if you have nothing at all to go by.

 

<i>Could a bad TOT sensor cause these problems? Is that on the same grey/red wire? </i>

That's the tranny fluid temp sensor inside the transmission, shouldn't cause them problems. Really no way for it to effect it.

I see the gray/red wire runs to the MPLS, have you driven in water lately, just before the problem started perhaps? Has it been replaced that you know of? I see lots of problems here with that part. Especially before the 94 model year?

On the 4x4 light, do you have a manual shift or electronic shift transfer case?

I gotta go out for a while, I'll check back when I return and see how you're making out with it.
Plenty of knowledgeable help here in my absence anyway, didn't want you to think I just abandoned ya! lol

 

That's amazing. Yes, about a year ago I drove through some water and immediately the charge light came on (luckily I was a mile from home) I limped home and had to replace alternator, battery, and starter. Now that you mention it, I think it did start right after that, occasionally at first and now every time I drive.

For the 4x4 light, I have the manual shift case, I think that started around the same time.

What is the MPLS?

Also, I checked my Haynes and don't see a grey/red wire in the diagram and I don't see it in the engine. Where does this wire run? What's the best way to test it, measure voltage on it with a multimeter?

I really appreciate the help.

 

Sorry posted that acronym wrong! The "MLPS" is on the drivers side of the transmission, "manual lever position sensor" reports the gear selected by the driver to the PCM.

My book shows Gray/Red wire for motors, 300, 302 and 460 maybe its wrong? Wouldn't be the first time. You'd didn't post what motor you have, if you did I missed it.

As far as the 4 wheel issue the switch on the TC may just be stuck. Do you know if the light does work? I'm kinda assuming it doesn't, the reason for the code?

I'd take a good look at the wires where they follow the top of the trans cross member and pass just under the front drive shaft. Look for any damaged wires there.

Then from your model year, problem you have and knowing it did get wet, I think I'd just replace the MLPS. My book shows no way of testing it. If it did get wet inside and slowly corroded over time it could be the root of all your evil. Shifting "manually" makes it function as it should?