Oh hey also found this connector on the ac compressor not sure if this could be related but this connector is obviously not in good shape

 

pin#41 has 12v power when I push the OD off switch (note the OD light in the cluster does not work) <<<=== isn't your OD cancel Lamp on the shifter **** with the OD push button ?

I know some Vans used the dash mounted OD cancel switch.

anyway when you press the OD Cancel Button then Pin 41 gets 12 volts and Pin 32 should toggle to Ground to turn on the LED

you indicate pin 32 has 12 Volts as long as it stays 12 volts the LED will not turn on indicating that OD is Canceled

IF you don't see that "Toggle" action then it still leads me to failure in the PCM
and IF the PCM will not communicate .... that is a sure sign that the PCM has issues since all other voltages seem to be present.

the AC connector is probably not a big issue IF it is making good connection to the Clutch Coil and is not shorted... while the PCM does look for AC on or off, it would not really care if the plug was disconnected .. it would run just fine but you would just have no AC

 

hey Lonewolf thanks for getting back to me, I thought there is an OD light in the cluster? My bad. I did a quick google search and see the way the light should be flashing on the shifter next to the button. Tomorrow I will check pin 32 for the “toggle” to ground action you describe. I did not even know it does that so very useful information thank you for that.

ok so let’s say the toggle action is occurring and so things are still looking good besides the no com issue. Could I back probe the connector on the pass. Side of the trans (in the solenoid 1 and 2 signal pins) to see which solenoids the pcm is powering when I select a specific gear?

So for instance if the case was that in first gear the pcm should power solenoid 1 and 2 when shifted to 1st. then I should be able to see if there is power to solenoid 1 and 2. Right? And if not then I would know I got pcm issues for sure. (assuming wiring tests good)

im assuming there is a specific combination of solenoid 1 and 2 being on or off for each gear.

not sure what the combinations would be though. If you don’t know off the top something tells me mark does. Lol.

Anyways Until I hear back from you guys on how the solenoids are activated to shift gears, my plan is to verify wires from pcm to tranny on pass side are good and also check this ground toggle function. I’ll let you know!

 

The shift solenoids have +12v power any time the key is on. The ground is either supplied or opened by the PCM to turn the solenoids on or off.

PRN SSA ON SSB OFF
1 SSA ON SSB OFF
2 SSA ON SSB ON
3 SSA OFF SSB ON
4 SSA OFF SSB OFF

 

well to start, i checked pin 32 to see if the PCM is toggling it to ground. I tested this by ensuring connector is plugged in to pcm securely and that connector bolt is tight. Then backprobing pin 32 and putting the other lead of my multimeter on the battery ground post.

Then i set my multimeter to continuity setting and observed to see if continuity was found when my wife pushed the OD off button on the shift lever.

My multimeter tells me there is no continuity from pin 32 to a good ground when the OD off button is pressed.

After performing this test I have concluded that the PCM is failing to toggle pin 32 from 12v+ to ground.

(please tell me if I have performed this test incorrectly)

I then studied the wiring diagram while thinking back to what mark said earlier; my vehicles symptoms match that of what would be caused when the solenoids are not receiving power. Well I have checked the connector at the pass. side of the trans and verified that all solenoids are receiving 12v+ from the PCM power relay. (including the EPC solenoid which is receiving power due to circuit 361 and 912 having a splice between each other)

Well, if these symptoms are representative of solenoids not receiving power, then I figured it could also be representative of the solenoids not receiving ground.

Basically this is happening because the solenoids are not operating. (hopefully, lol)

Anyways, I verified the solenoids have power, so I figured the next logical step is to check for ground to solenoids.

Since the solenoids receive power from the pcm power relay at all times, I am assuming these solenoids are operated by a ground signal.

I believe this ground signal must be sent from the PCM because the solenoids are not wired to anything else according to the diagram.



After lonewolf informed me that the PCM is suppose to toggle pin 32 from 12v+ to ground, I figured that this is most likely what it does for pins 19 and 52 (pins that are for shift solenoids 1 and 2) in order to provide ground to the solenoids so they can operate.

Because I can not observe this toggle to ground in pin 32, I thought it is possible that the PCM is also not toggling pins 19 and 52 to ground in order to operate the shift solenoids.

So i backprobed the wires for shift solenoids 1 and 2 in the connector at the pass side of the trans, and connected my test light to a good ground (ground strap on the frame under the pass front door) and then to the back probe.

The signal wires for the solenoids have 12v+ coming from the pcm in both of them so the test light stays lit up when I connect it to either one.

in theory the test light should turn off when the pcm switches the signal wire from 12v+, to ground.

So i checked each signal wire one at a time, shifting to each gear watching for the light to turn off.

The test light never turned off.

so I have concluded the solenoids are not receiving ground from the PCM as they should be, therefore solenoids are not working.


I'm pretty confident that the truck needs a PCM now.

Please let me know what you think guys. Tell me if I did anything wrong when performing my electrical tests. I am no veteran when it comes to electrical problems.

Note! this is only a conclusive diagnosis provided the pcm operates the solenoids by toggling pins 19 and 52 from 12v+, to ground. Please let me know if the solenoids are operated in a different fashion.

 

yes the PCM switches the "Ground" side of the solenoids to enable them....

when I do this test, I use a Voltmeter .... I connect the Black Lead to a Good Ground and watch for the Voltage to drop when the solenoid is enabled.

using your meter in the Continuity Mode on a Powered Circuit is a NO NO as it could fry your meter.

the same goes for watching the Return side of the LED ...



this image is just an example to explain........ Let's just say the 3V is really 12V .... the switch and 3K resistor and that Transistor is inside the PCM... when the PCM sends the signal to close the switch it Turns on the transistor which then conducts to Ground causing the LED to turn ON.

so what you are effectively wanting to do is Measure the Voltage Drop across the Transistor..... when the transistor is turned off you will see a high Voltage across it, when it is turned on you will see a Low Voltage indicating that the Transistor is Actually Conducting.

this same example can be said for the solenoids just Call the LED a solenoid and same difference.

I hope this explanation makes sense.

 

this mostly makes sense to me Lonewolf I just did some quick research and learned briefly of transistors and their basic functions, etc. so I was able to form an understanding of the diagram you posted there. now I Have a good understanding of how the pcm switches ground to a circuit. Just to clarify on testing this voltage drop, is the correct method to put my ground lead on a good ground, then my red lead on the wire to be tested? (So if I was testing that led in my shifter I would back probe pin 32 with my red lead) THEN I would watch for the voltage to drop below 12v when the button is pressed?

im sorry if that is an annoying question! Kind of feel like an idiot right now, some of these concepts are just outside of what I’ve been taught so far, I’m learning a lot from you as I go through this.
oh man! I forgot to mention that if I back probe pin #32 with a jumper wire and run the jumper wire to good ground then the OD off light in the shifter comes on! Which tells me light is in working order and is in fact experiencing an absence of ground when button is pushed like you suspected lonewolf. I thought I may be able to test solenoids using this method.

 

(So if I was testing that led in my shifter I would back probe pin 32 with my red lead) THEN I would watch for the voltage to drop below 12v when the button is pressed?

Correct, and the same to be true for testing solenoids, I just Picked the OD LED as a good test to see if the PCM was alive because it can be done with the engine not running. under normal conditions with just the Ignition Switch in the RUN position Engine OFF the OD LED will toggle each time you press the button.

since you already checked voltage on the PCM Drive pins for the Solenoids and you are reading 12 Volts I would say the solenoids are not Open as they are passing the Common Supply Voltage... you can check resistance of the individual solenoids with Batteries disconnected BUT right now this is not your Problem so No need to test them at this point.

 

ok sounds like a plan I will check for that voltage drop today Well I gotta head in to work but after I’m off I will be able to get out to the truck. I’ll report back this evening to let you know what I find out

 

Ok checked voltage on pin 32 while pushing the od off button- voltage does not change whatsoever.

checked voltage on pins 19 and 52 while shifting through each gear- voltage never changes at all.

pcm is not switching the ground side of the solenoids to ground.

where do I get a pcm from ? Can this be bought at An auto parts store? Ford dealer? Or junkyard/used only?

thank you 1,000,000 times lonewolf and mark!

 

I got mine off FleaBay for like 50 bux... After I finally figured out which one I needed.

what I ended up with was an OEM Ford F4TF-12B565-AA

I don't know what number you have in your truck .. but here is the Post I did when I was sorting these numbers out ..... https://www.ford-trucks.com/forums/1...3-f250-xl.html

 

ok sweet I just read your post so I will need to pull the pcm out and check the part number in order to know what replacement I will need? When searching online there are some for high altitude emissions and some not.

 

that would be the easiest way. it's pretty hard to read the tag while it is in the Vehicle.
you can replace it with the Exact number type or choose an upgrade if you don't have the latest one.

you can see some pics of the tag on mine here ==>> https://www.ford-trucks.com/forums/1...l#post18655181

 

BTW there are some aftermarket controllers IF you have Deep Pockets .......so that is something you might look into ..... I wasn't interested.

it's easy enough to convert it to a manual shift BUT you will need a PWM valve controller for the EPC...

I have designed a Test controller using DRV101 IC ... I have used this to replace the VRV on the C6 Tranny and it works fine .. it also controls the EPC just fine.

you can use the original MLPS switch signals with minor logic and a solenoid Driver board to select the solenoids to engage depending on where the shift lever is positioned... the TCC is manually controlled and you won't have any automatic Kick down control... it would be easy to Trash the Tranny using this method so I won't Post my schematics. but I have just given all the info needed to build one the solenoid select pattern is already given in this Thread too.

 

I don't understand this. The EPC is a variable force solenoid, not a PWM. It controls pressure based on the current supplied to it. Are you saying you can use a PWM controller to do this?

I built a controller without any logic boards to do this. It was for a specific racing series that didn't allow any type of computers, and even a simple logic board was considered a computer.

It worked, for a while. The forward clutch drum cannot handle max pressure and this system had no provision to reduce pressure when in 1, so the forward clutch drum blew apart.