Flashing OD Light / P1747 Code
 

2001 Excursion 7.3L PSD Banks Powerpak 4r100 Trans.
I've had an intermittent problem with the OD light flashing and the truck going into limp mode. Now it's consistent and I need to do something about it. Transmission shifts fine in all gears and the ATF looks good, but I am concerned that I grossly overfilled it. P1747 indicates a short related to solenoid A. I chased the wiring harness from near the master cylinder all the way back and found no obvious damage from heat/etc. Pulled the plug on the right side of the trans case at the solenoid and found a small amount of ATF present. Pulled the pan, cleaned the connector, and replaced with correct amount of ATF. Truck is the same - still shifts fine, but goes into limp mode and the P1747 code comes back every time I clear it. Suggestions?

Check the wiring. What you did was look at the wiring. You need a DVM and the know how to use it. It could also be a bad shift solenoid.

I have the equipment and the skills, but no diagram. Is this the correct test procedure for my issue?

All three of those items are powered from the SAME input voltage. It's yellow/black coming off of FUSE 113 in the underhood fuse box, goes thru the PCM POWER RELAY, coming out a VIOLET wire back into FUSE 19 in the underhood fuse box, DEPARTS the fuse box a RED/YELLOW wire. From there it goes to a split, named S122, apparently near the dash(not sure why?), to another split at a point called S138, apparently in the backup lamp harness. From there it goes to the TRANSMISSION CONNECTOR, PINS 1 & 12. Power on pin 12 is distributed to the TORQUE CONVERTER CLUTCH SOLENOID, COAST CLUTCH CONTROL, SHIFT CONTROL 2, & SHIFT CONTROL 1. Power on pin 1 is distributed to the ELECTRONIC PRESSURE CONTROL SOLENOID. Those Items in blue all relate DIRECTLY to your codes, so this is why we are troubleshooting the voltage here. Goes without saying, but if either of those fuses is blown, replace, clear code, check drive, re-check fuse, cause when they blow, it was for a reason and may have blown again.

STEP 1: Is your third brake light burned out? Please don't ask me to explain this one, just check, and change it if it is. If it was burned out, clear codes, drive to see if problem persists, if so, continue to STEP 2. Again, please don't ask to explain this part.
STEP 2: Pull FUSE 113, check for good voltage on ONE side of it's plug(won't be on both since the fuse is pulled). You will probably get voltage here since the fuse box is immobile and unlikely the cause. If good reinstall the fuse, if bad, find a way to get voltage to it. On to STEP 3.
STEP 3: Pull FUSE 19(20A fuse). Turn Key to the RUN position, this will engage the PCM POWER RELAY. Check for Voltage on ONE side of the plug(same reason). If bad, suggest replacing Relay, and repeat test(keep in mind, I'm not getting into that fact that the Violet wire off the relay goes two places, mostly because I'm expecting the relay is good). IF voltage was good, turn car off, reinstall fuse, turn Key to RUN, check for the same voltage at the same fuse(check at the metal tabs on top of the fuse). WE are now testing to see if it is shorted past this point, if the voltage is gone we DEFINITELY have a short. Continue to Step 4
STEP 4: Time to get dirty. Remove the transmission Connector on the transmission(this isn't the DTRS, I believe this one plugs in on the passenger side closer to the rear of the trans before the transfer case, it should plug directly downward.) IF you previously measured a short, or didn't get voltage at the fuses during any previous steps, REPEAT STEP 2 and 3, check to see if the voltage has reappeared at the fuses. Im suspecting a shorted solenoid, or a shorted wire. Continue to step 5.
STEP 5: With the transmission plug still disconnected, and the key in the RUN position, we should see 12 Volts on pin 1 & 12(both of these are still going to be red/yellow). If you are missing voltage on either, then I suggest you switch to a resistance reading and check for ground on either pin. ALERT, THIS IS WHERE WE MAY FIX A PROBLEM WITH A PERMANENT MODIFICATION. IF either wire is missing voltage, BUT one wire has voltage, you are going to CUT the non electrified wire about 4in from the plug, and short it to the electrified wire.(an inline splice would work great here, as someone should have told the for transmission engineers). IF you have good voltage on BOTH wires proceed to STEP 6, unfortunately this is where it gets a tad bit more complicated.
STEP 6: According to the wire diagram, all the input power is being supplied to solenoids, about 5 of them, which means to a multimeter you will only read a very low(or no) resistance across each of the solenoids. The wires we will be working with are as follows, all located at the transmission connector. White/yellow, pin 11, output of the Elec Pres Control Sol.; Violet/Yellow, pin 4, output of the Torque Converter clutch sol.; Violet/orange, pin 2, shift control 2(also known as SS2, or shift solenoid B). Turn the vehicle off, disconnect the red battery cable and all the connectors attached to the PCM(all because I can't remember if you have multiple, and if so which one it is)(battery disconnect is more for safety of the PCM). Now, for the resistance checks. IDEALLY you would check from the pins on the PCM connector to the pins on the transmission connector, UNFORTUNATELY, that requires multiple sets of hands and a really long test lead. If you have those items, then I will list the pins you will test below this step and you will be looking for a low/zero resistance. IF you don't have those items, thats ok, we can almost do the same thing. Attach one test lead to the chassis, make sure you have a GOOD connection, in fact, first thing is to test that connection by touching another part of the chassis and looking for lo/zero ohms/resistance(or the light comes on a powered tester). Check each pin, 11, 4, and 2 against the ground. IF any of them give you anything BUT a hi resistance/no light condition then that line has a short and will need to be replaced(don't waste money on a wire harness, just get some 16 guage and zip ties, cut at each end of bad line and run the new one inline.). IF each wire test good, no short to ground, then that means you have NO shorts in the SYSTEM WIRING. Having said that, you should be able to connect everything BUT the PCM connector back and we will move on to testing for the voltage at the PCM. Keep in mind, we just skipped clear past testing the solenoids in question. If you can get a mirror and some space, then we will cover that portion two steps from now. The reason we aren't testing each of them is Because they are solenoids, and appear to always have a short, and will test as such. Their is no reason to assume more than one solenoid broke at the same time which is why we are looking for a open/short wire outside of the transmission. The pins on the PCM are as follows: White/yellow, pin 81, EPC(this comes from the elec. pres. cntrl. sol.), Violet/yellow, pin 54, TCC(torq convert clutch sol), Violet/Orange, pin 11, SS2(aka shift cntrl 2, shift sol b). Proceed to whatever long-winded step I came up with next.
NEXT STEP(lost count): Everything connected normal, with exception to PCM connector(s). Turn Key to RUN. Verify one more time you have good voltage at FUSE 19(using top posts, leave fuse in). Check each of the THREE previously mentioned pins(11, 81, 54) at the PCM for Voltage(not sure what should be here, but it should be above 2 and I think less than 11). If you are missing voltage on any of those lines, then you have a broken(open, not shorted) line, or a bad solenoid on that respective line. If all three are good, then My LAST recommendation is replacing the PCM, as it shouldn't be popping a code if all three of those are good signals.
LAST STEP: If nothing else appeared bad, or you don't want to replace the PCM yet, or you just want to know for sure, then you can pull each solenoid out individually and inject a voltage and ground to see if it engages(problem is I can't even picture in my head what these specific solenoids look like, or if you'd be able to hear/see them engage).

Hope this helps and saves you some money. If it's the PCM, carparts.com, get the EXACT part number you have on your current PCM, or it AINT GONNA WORK. Wow, I'm long winded. Dude with the Econoline, I gotta go, but I'll get you a write-up that says the exact same things, but with the correct wire colors and fuse numbers, sometime tomorrow, sorry I can't get it tonight.

No, that procedure has you checking the power to each solenoid. If that were the problem you would have a code for each solenoid, not just one. The problem is on the ground side of the solenoid. The first place to check is remove the connector on the passenger's side of the trans. Check each pin on both sides of the connector for damage or corrosion. Then you can check the resistance across shift solenoid A through the transmission side of the connector. Someone has a diagram of that connector, but I don't. If the solenoid checks out you need to check the wiring from the PCM to the harness side of that connector. Check it for opens and shorts to ground or power.

Thanks Mark, I found the problem (I think)

I checked for voltage on what I expect were pins 1 and 12. One was over 12 volts and the other was 5. The previous owner had installed a Banks transmission controller as part of the Powerpak kit. Once I pulled the harness apart and isolated the lead that the Banks unit was "taking over" I was able to disconnect the controller and install a jumper to return the system to stock.

Code disappeared and no issues - everything normal. The Banks controller box was severely corroded - I expect the internals deteriorated over time which explains a lot of the strange behavior and intermittent problems I've been having.

Thanks again for your help.