P0750 - will not go away, tried everything.

This is an ongoing issue so bare with the long story.

About 6 months ago my OD light started flashing for about 10 seconds and went away. Read the pending code (P0750) shift solenoid A malfunction. The transmission did not change in any way. Still shifted excellent even at the time it was flashing.

I ignored it until it did it again in about 150 miles. Same thing, came on breifly stored a pending code but the transmission did not fail or change in any way. This time I figured I wanted to put in a shift kit anyway, ill drop the valve body and change the solenoid. I installed the shift kit, new valve body gasket, sonnax valves and o-ringed end plugs, new solenoid, new reverse servo gasket. All the internal solenoid wiring looked perfect.

Once all back together it drove great, the kit really firmed up the shifts and made the trans engage much quicker. But after 300 miles the damn light started flashing again.

This time I reset the computer and started looking at external wiring. I could find no problems in the wiring harness but the connection was a little dirty and the gasket was a tad dried up so I thoroughly cleaned it and coated the gasket with dielectric grease and the problem went away for another 150 miles.

Today bam... Back on again for 10 seconds then went away. This time it came back 5 minutes later and actually set off the check engine light. Same code P0750.

Freeze frame is always the same vehicle speed about 20 mph rpms about 2,000. And ZERO problems shifting.

Truck is an 09 regular cab 2wd 2.3 auto 5r44e with 66,000 miles. Fluid and filter is changed regularly, very clean. Also has an secondary trans cooler. Again there are NO physical symptoms associated with this code. The transmission drives great, doesnt go into limp mode and if the light wasnt on you would never know there was a problem.

What in the $&@%$&$& anyone got any ideas where to start chasing this problem again? Seems like I can just reset the computer and get another 150-300 miles before it will come back so I've been thinking this could be a ECU/software issue but no idea? With no physical issues it just seems logical it has to be a computer or electrical problem. If the solenoid, valve, or anythjng mechanical was failing i would assume it would stop shifting properly!

I wonder if there is a pid for the solenoid A resistance? If so you could set that to read in Forscan and go around wiggling wires until it shows open circuit.


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If there is my bluedriver and CRP129 cant access it. I did test the resistance (was within spec) and I manually energized the solenoid with 12 volt to verify it does/can open a close (it does).

I ordered a wiring diagram for the truck which hasn't arrived yet so I can find and test the pin from the ECU down to the transmission connection. If I can get my meter on the proper pins I could do the wiggle test with that.

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Your awesome. Thanks. Gonna go "wiggle test" the circuit now.

Just tested the wire for SSA at the trans connection to pcm connection. No issues with the wire, wiggled the crap out of it through the entire length and not a blip on the screen. No visible damage anywhere either. The pin at the pcm is also clean with no visible corrosion or damage. I have no idea what else I can possibly test or check. Ive now verified the internal and external wiring to the solenoid is good, solenoid itself is good, valve body and gaskets have no pressure leaks, fluid is clean and filled properly and as always shifts fine.

Had the battery disconnected while testing the wires so the pcm got reset again, took it for a test drive. Still drives perfect and the code is gone for now. It will certainly be back in another 150-300 miles though.

The solenoids all get 12v from one common wire with key on
The computer reads that 12volts as it passes thru the solenoid(just a coil of wire) and to the computer on its Ground wire, so computer can tell if solenoid is getting and passing that 12volts
Computer grounds each solenoid's wire to activate it

Anytime you have any OBD code you need to look it up on a full list, not just google it
Full list here: https://therangerstation.com/tech_library/OBD-II_codes.shtml

For solenoid A(1) we have these:
P0750 Shift Solenoid A Malfunction
P0751 Shift Solenoid A Performance or Stuck Off
P0752 Shift Solenoid A Stuck On
P0753 Shift Solenoid A Electrical
P0754 Shift Solenoid A Intermittent

Computer didn't use 753, electrical fault

It didn't use 751 or 752, solenoid stuck on or off

It didn't use 754, works GOOD but only once in awhile, intermittent

It did use 750, malfunction, but not electrical malfunction

Narrows it down but not specific

A solenoid slides a rod that opens and closes passages that send fluid pressure to different clutches and brakes.
It does this alone or in conjunction with other solenoids to get the pressure where it needs to be.

Solenoid interaction seen here: http://www.atra.com/Gears/2003/2003-05/2003_5_50.pdf

A non-electrical malfunction would most likely be detected by intermediate shaft speed sensor, the ISS, its speed didn't change to parameters specified when selected solenoids were activated.
And it didn't do it just once(intermittent) it does it all the time.
Non-electric fault codes can take awhile to come back, computer has to see a "problem" repeated a few times before it will set a "pending code", and then that has to repeat a few times before is sets a code and turns on CEL.

Did the seals on the solenoid rod get changed, never took one apart so just asking

I have read a few posts where solenoids tested OK, but spring inside was weak, so didn't push/pull rod back into closed position when in operation




OR............could be a computer malfunction

When I had the valve body out I actually upgraded the valves (rods) the solenoid controls with ones that have o-rings ends to prevent leaking. The original valves had no o-rings. Sonnax claims these help prevent solenoid codes due to pressure leakage.

Its odd that P0754 is specifically listed as intermittent because like I said the P0750 I get only comes on intermittently for 10 seconds or so then disappears and will eventually clear itself before setting a stored code. So I'm getting a code thats not specifically for an intermittent problem that happens intermittently?

The old solenoid itself tested good but was replaced anyway and the new one also tests good (at least electronically). And again if it was mechanically failing to open, how is it still shifting perfectly? At no point during all this has there been a physical symptom of any shift malfunctioning.

Could there be a fault in the speed sensor? Seems unlikely since I imagine I would get errors for multiple solenoids not just one. Or a gear ratio code.

According to the link shift solenoid A is active in first - third and reverse so active alot. Failure in this solenoid seems like it would cause issues all over. I hate problems like this...

Any way to test the computer is not the problem?

No, no way to test computer, but you could check with Ford Dealer, VIN in hand, to see if there is a software upgrade available

How do you know P0750 is the cause for the temporary CEL, or OD light, if code doesn't store?

Or do you see it on a live scan while driving?


Usually its the other way around, transmission is slipping or ??, and no codes.....yet, lol.
Which is why I suggested computer issue

Check the voltage sweep on the MLPS. I will try to find a chart and post it.


Here you go

This just gets more and more complicated lol. Getting above my pay grade!

I will see if I can perform this test tommorow morning. Thanks for the info, I will report back! I didnt think the range sensor was any part of controling the solenoids but ill take any and all info, ideas, or tests i can!

I know my range sensor has a messed up bushing on it....

Serves a big part in shift strategy. PCM uses its signal for determining what gear the transmission is in.

Fair enough. I always just assumed they were overly complex neutral safety switches.

Ok, both my scanners just aren't good enough to read the PIDs for the range sensor voltage. Any way to do it by just backprobing with a multi meter or test it off the vehicle? I dont know if you remeber my other post about the shifter being incredibly hard to move, Ive determined that is the result of the range sensor being super hard to rotate, and the plastic collar is cracked so at this point I'm ready to just replace the damn thing anyway. However id like to see if it is or isn't related to the p0750 issue and not just wait months seeing if the code comes back lol.

Can’t test it off of vehicle. Here is more info that my help with diagnosis.