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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 44502
Experience:  16 years experience
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2011 F150 3.7 RWD I disconected the tranny wiring harness

Customer Question

2011 F150 3.7 RWD I disconected the tranny wiring harness from the PCM because i had to work on something end did not want to toast the PCM. I fixed the original issue but when i connected the harness i started getting a bunch of codes Code: P0742 - TCC
Circuit Stuck On Code: P0743 - TCC Circuit Electrical Code: P0748 - PCA Electrical Code: P0960 - PCA Control Circuit Open Code: P0962 - PCA Control Circuit Low Code: P0753 - SSA Electrical Code: P0973 - SSA Control Circuit Low Code: P0755 - SSB Code: P0758
- SSB Electrical Code: P0976 - SSB Control Circuit Low Code: P0760 - SSC Code: P0763 - SSC Electrical Code: P0979 - SSC Control Circuit Low Code: P0768 - SSD Electrical Code: P0982 - SSD Control Circuit Low Code: P0960 - PCA Control Circuit Open Code: P0962
- PCA Control Circuit Low Code: P1397 - System Voltage Out Of Self Test Range i sprayed the connector on the PCM and the harness side with the electrical cleanup spray No effect i disassembled the harness connector - no visible problems. tested the continuity
on every line in the harness. all good. i tested against ground. good resistance everywhere The engine starts so it does read signal from the transmission BUT you can stall it supper easy which does mean that the communication between the tranny and the PCM
is not good. with key at start position and engine not running you can hear one of the solenoids in the tranny clicking I DO HAVE the OEM service manual and could not find anything helpful. I am not going to throw parts at the problem hoping that one of them
will fix it. All the parts are expensive so swapping any of them before 100% certainty that they are at fault, is a no go.
Submitted: 1 year ago.
Category: Ford
Customer: replied 1 year ago.
Please assign my question to Ron
Expert:  HDGENE replied 1 year ago.

Hello, most common problem I have seen is when you reconnect the trans bulkhead harness it can break off one of the pins inside the transmission, take a better look inside the trans bulkhead connector and see if one of the pins is broken off. This can cause all of these codes. If no other thing to check would be to see if a fuse is blown which controls the transmission and not sending power to l\turn the solenoids on.

Expert:  HDGENE replied 1 year ago.

If you would like Ron to help you let me know and ill opt out of the question

Customer: replied 1 year ago.
please let Ron help me out
Expert:  Chris (aka- Moose) replied 1 year ago.

It appears Ron is not wanting to address this post or he would have replied. If you would like me to help, let me know.

Customer: replied 1 year ago.
Good point. Please do
Expert:  Chris (aka- Moose) replied 1 year ago.

Welcome, I am Chris (aka-Moose)

One would think since all you did was unplug the PCM and there were no issues prior then the issue should be with what you touched, the connector wires and pins. Now you did not mention your prior repair, which may have something to blame on the current issue if that repair resulted in a short is a wire or the PCM. I think its best to do the diag steps for any one of these codes to see where it points to look for the issue. Like any one of the solenoid electrical codes. Since you have the Ford repair guides, I assume you do not need a copy of those tests. If so let me know. Prior to doing diag as well as knowing any of those results it sure looks like an issue with the power VT/GN or signal return GN/WH between the PCM and transmission.

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Thanks Chris

Customer: replied 1 year ago.
Chris, the prior issue was with a connector on another harnesses. I don't see how that can be related. I told you that I could not find any short wires. I told you that I can start the engine so the PCM is not the problem. I told you that I have the manual so I obviously tried the suggested diagnostics. You can't help me by telling me to try something I already told you I did
Customer: replied 1 year ago.
Chris, still with me?
Expert:  Chris (aka- Moose) replied 1 year ago.

Lets pick a code and work through each of those tests, will that be okay? I find it very odd there are 18 codes and none of the tests for those codes found any circuit issues. You can still have a PCM failure and the engine still run. Not that I am saying the PCM is bad but diag has to be done to confirm its not or is bad.

Customer: replied 1 year ago.
Chris, most (if not all) of the codes point to pinpoint test A. So, you don't have to chose.As i said, I tried the test sequence before i requested help. I would not hurt to try again, so i did it this AM. This time pulled the harness from below the car so it is easier.A1 CHECK THE SOLENOID POWER CIRCUIT FOR VOLTAGE , Yes
A4 CHECK SOLENOID CONTROL CIRCUITS FOR AN OPEN , Yes (not just the 7 listed, all of them are OK)
A5 CHECK SOLENOID CONTROL CIRCUITS FOR A SHORT TO GROUND
now this test does not make any sense. IF you at this point the harness is disconnected on both sides which is the logical situation if you follow the diag path so far. The chance that the resisitance is less than 10,000 ohms is practically 0. because at this point the harness is "in the air" (ignoring the O2 sensors). to make this test somehow meaningful i tested for short between these lines and line 11. No luck.
If however the C175T IS connected then resistance between 7 (ignition voltage) and the ground is 1500 ohms. No sure how meaningfull is that because at this point you are measuring the resistance of the PCM
So let's assume that we passed A5 and we are on A6
A5 CHECK SOLENOID CONTROL CIRCUITS FOR A SHORT TO GROUND
the first step here is Connect: PCM C175T (3.7L Engine). which makes me think that i am correct assuming that in the previous step the harness is disconnected on both sides and you are measuring the electrical resistance of the air in your garage.
Skipping over this and moving on, we need toMeasure for voltage between the transmission vehicle harness C1575, harness side and ground using the following chart.At this point the harness is definately connected on the PCM side but I am not sure that it should be connected on the tranny side. In fact if it is (and the tranny is on the truck) measuring these voltages will be practically impossible. No space whatsoever.So, lets's assume that C1575 is not connected. None of the voltages in the suggested lines is more that 2.5V. ( as i said in my first note, when the ignition is on there is a clicking sound in the tranny, which would make sense if you trying to energize a solenoid with less than the required power. OK, so maybe despite all the testing so far there is a problem in the harness? To check that let's remove it from the test and see what is the voltage on the appropriate pins at P175T. Same as on the end of the harness. At this point the PCM is the prime suspect. Unfortunately i can not convict it. Why? Because the PCM is like a electric bulb it either works or not. There is no "in between". And this PCM seems to work. Why do i think so? Again, you can start the car and move it. I know that you said that it is possible for the PCM to be bad AND for the truck to run, but i have a tough time believing it. I need a proof?So, here is what I need from you:
1. I would honestly be happy if you find an error in my reasoning. This problem is driving me crazy for more than a week
2. If you can't do 1. Can you suggest a test to check the PCM?
Customer: replied 1 year ago.
Something I forgot - i downloaded FORScan and tested the truck with it - no issues with the PCM popped up. Used few other more generic apps too, same result.I am missing something, what is it?
Expert:  Chris (aka- Moose) replied 1 year ago.

A5 the PCM is not connected the trans is not connected, your testing at the trans connector to see if any circuits are grounded. We can not assume the tests passes, it has to be done.

A6 the PCM is connected the trans is not connected and your seeing if any wires are shorted to power.

I would need those tests done correct to move forward.

A PCM is just a computer, I am sure you have experienced a computer failure where as parts of your operating system worked and others did not and sometimes when you turn it off and on it then works again or gets worse.

Customer: replied 1 year ago.
Chris, i am getting the feeling that you did not read my post. Please do. I spent a lot of time explaining what i did (AND why some of the things do not make sense to me). I am hoping that you can find an error in my reasoning, but for this to happen you need to read it firstA5 I did not assume that the test passes. I did it. However if the harness is disconnected from both sides PCM and Tranny, where the ground connection can possibly come from?A6 i did the test based on the manual (which is as you describe it above). Again, please re-read my post.I have MSc in electrical eng (computer hardware). PCM is just a computer? Do you know what a computer is? Do you understand that the parallel you are making is COMPLETELY wrong? Do you understand what is the difference between hardware and software? Do you understand that the software on the PCM is a light years simpler (and robust for this reason) than a computer? Do you understand that the PCM does not have OS. Do you understand that ANY glitch with hardware will kill the whole thing not just the tranny?Chris, for a third time. Please re-read my post. I am not an ASE certified mechanic but I AM an electrical engineer. I asked for very specific thing. Find an error in my reasoning. Please. If you can't, please point me to a place in the manual where i can see how to test the PCM.
Customer: replied 1 year ago.
Chris, still with me?
Customer: replied 1 year ago.
Chris, please let me know if you gave up
Expert:  Chris (aka- Moose) replied 1 year ago.

Its Halloween, I was out with my boys. I read your response word for word and based my response, on the issues you mentioned on test 5 and 6. You wrote "So let's assume that we passed A5 and we are on A6 A5" Which is why I used the same terminology (assume).

Test A5 tests for a short within the wire harness to another wire or the chassis.

Yes I know what a computer is, I am a Ford tech, trained in diagnosing them and working with a computer right now.

Yes a PCM does have a OS, it boots up and runs through a series of tests and basis its operating strategy on its findings. Then it stores a memory and basis future starts on what it learned from the previous ones. It also requires frequent updates.

In pinpoint test A we have to please every single test and address any test that fails.

Again I am and have read word for word everything you have written.

So it appears we are up to test 7 now?

Customer: replied 1 year ago.
however the manual suggests that the problem with the low voltage are the solenoids which is outright crazy because they are not part of the test at all
Expert:  Chris (aka- Moose) replied 1 year ago.

What do you mean by the solenoids are not part of the test at all?

All of pinpoint test A is about the solenoids.

PINPOINT TEST A : TRANSMISSION CONTROL SOLENOIDS

Customer: replied 1 year ago.
my bad, i actualy thought that the voltage MUST be >4V. a week ago when i did it for a first time i had it right but i've spent so much time on this that i am at the point not to know what is up and what down.I am on step 7. I'll measure the solenoids tomorrow AM (too beat now). I can not see how all of them can go bad at the same moment
Expert:  Chris (aka- Moose) replied 1 year ago.

I doubt all the solenoids have failed.

Customer: replied 1 year ago.
as expected. all are within spec. Now?
Customer: replied 1 year ago.
the only thing i can think of is a lose wire, which test well but does not work under load. i checked everything i could. I am back where I was when i asked for help
Customer: replied 1 year ago.
Chris, how can i test the PCM?
Expert:  Chris (aka- Moose) replied 1 year ago.

Since the outcome on test 7 was (yes) did you follow those steps indicated in the pinpoint test?

You would need a code related to the PCM to perform a test on the PCM.

Test A3 would of needed to fail to blame the PCM. That is the PCM test your asking for to do related to these codes.

Customer: replied 1 year ago.
Chris, i spent two weeks on this to no avail. Tom AM the truck will be towed (if needed) to a dealership
Expert:  Chris (aka- Moose) replied 1 year ago.

Okay, best of luck.

Expert:  Chris (aka- Moose) replied 1 year ago.

What did the dealer find wrong?

Customer: replied 1 year ago.
the PCM
Expert:  Chris (aka- Moose) replied 1 year ago.

Glad I was able to help from my first post on the 30th saying it would be a wire short or the PCM and all the tests we did, ruled out wire shorts. Glad its now resolved.

Customer: replied 1 year ago.
Chris, I am missing something. What did you tell me that I have not already read in the service manual before I asked for help?
Expert:  Chris (aka- Moose) replied 1 year ago.

I wrote in my first response this would be a wire short or the PCM to blame. So we worked through all of the tests to rule out the solenoids and the wiring. Since the PCM was bad that does indicate step A3 I mentioned had to have failed. Leading to needing to replace the PCM which was the fix. If you choose not to rate my answer that is fine, it is your choice. The website will hold your funds for the next question you ask.

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