Access to/location of transaxle vehicle harness connector for P0755 DTC troubleshooting - Focus Fanatics
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Old 08-31-2011, 04:48 PM   #1
JD_Hupp
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Access to/location of transaxle vehicle harness connector for P0755 DTC troubleshooting

I'm continuing to work on the problem posted here: http://www.focusfanatics.com/forum/showthread.php?t=263872

I find that driving with O/D off, when I hit 50 mph the engines races a bit and then slams into engagement. And I get pending/continuous code P0755. This is the same full DTC I get if I drive with O/D on, at which point the race/slam behavior happens at any and all speeds in the 3rd/4th range.

P0755 indicates a fault in the Solenoid B circuit, but I already replaced solenoids A and B.

Because the torque converter clutch is supposed to apply at 50 mph, and because no-TCC-apply-in-3rd-or-4th is one of the listed symptoms of a P0755, I think that I'm looking at a TCC control problem, and that the problem is not in solenoid B but elsewhere in the circuit. Candidates include the transaxle vehicle cable harness, the transaxle's internal cable harness, the TFT sensor, and a few other things.

With the equipment I have (and don't have), it makes a lot of sense for me to do my best to check the wiring and the TFT sensor. I have found the PCM and can get at it easily enough for testing (no thanks to the workshop or wiring diagrams manuals -- that info is probably in the powertrain control/emissions diagnostics manual, which I don't have).

But at the other end, where exactly is the transaxle vehicle harness connector, and what it is the best way to get at it for wire testing?


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Old 09-02-2011, 09:55 AM   #2
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OK, answering my own question: The transaxle vehicle harness connector connects to the "transmission hardware unit," which is located on the front side of the transaxle a couple inches above the transmission range sensor.

To remove the connector, squeeze or press in the tab on the side of the connector while pulling or prying up the connector.

The way to get at the connector is by removing the battery and battery tray. If you need to power the system for prescribed pinpoint tests, connect the removed battery to the battery cables via jumper cables.
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Old 09-02-2011, 08:32 PM   #3
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You may have a hydraulic problem with the direct clutch. Ford has two types of codes. On -Demand are electrical faults that are there at the time of testing. Then there are continuios fault that are stored in memory. If you think you have an electrical problem, clear all your faults using your scanner. Start the car to idle up to three times but do not drive it. If you have a wiring or component problem, the code will come back after the 3rd key cycle. If it does not, and it only comes on after driving, you probably have a problem with the direct clutch. The code p0755 turns up because it doesn't see the proper gear ratio for 3rd gear and it generates that code because it knows it's a prolem with that soleniod hydraulic or electrical circuts. Just did a transit connect trans with the same problem (uses a 4f27 like a Focus) and it rolled thge direct clutch seal off the piston. If you have a lot of miles on the car, you could have a similar problem. Not a lot of support in the rear of that trans at the direct clutch and the rear cover so pressure loss is a problem. Don't go crazy looking for an electrcal problem, because chances are it isn't.
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Old 09-06-2011, 01:51 PM   #4
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Quote:
Originally Posted by fordtech122 View Post
You may have a hydraulic problem with the direct clutch. Ford has two types of codes. On -Demand are electrical faults that are there at the time of testing. Then there are continuios fault that are stored in memory. If you think you have an electrical problem, clear all your faults using your scanner. Start the car to idle up to three times but do not drive it. If you have a wiring or component problem, the code will come back after the 3rd key cycle. If it does not, and it only comes on after driving, you probably have a problem with the direct clutch. The code p0755 turns up because it doesn't see the proper gear ratio for 3rd gear and it generates that code because it knows it's a prolem with that soleniod hydraulic or electrical circuts. Just did a transit connect trans with the same problem (uses a 4f27 like a Focus) and it rolled thge direct clutch seal off the piston. If you have a lot of miles on the car, you could have a similar problem.
That is very interesting and you'll read at the end of this post some application of it.

But you sound like a guy who could answer this question: Pinpoint Test B5 from the FSM is checking for a short to ground in the vehicle harness or PCM. And indeed, I find 0 ohms for pin 4 but 11.5 Kohms for pin 5. When I run Test B6 -- same test with the PCM disconnected -- pin 4 tests around 400 Kohms. This seems to indicate a ground-short problem in the PCM. And if I pull the PCM and check it directly, I get 0 ohms between pin 91 (to which pin 4 from the vehicle harness connects) and pin 103 (an un-switched ground).

Since pin 4/pin 91 is a "sensor signal return (reference/ground)" I wondered if maybe is was OK for it to connect to ground. So I tested other pins with that same function in the PCM to see if any of them were shorted to ground, and none of them were except pin 76. Pin 76 is shared with a "sensor signal" function, which I didn't understand. But at any rate, it seemed that maybe pin 91 really should not short to ground.

Can you confirm that this indicates a problem with the PCM?

MORE HISTORY: I started with a problem in which I was getting (in 3rd and 4th gear ranges) shuddering, or worse, engine racing followed by a slamming into engagement. Codes were P0750 and P0755. I replaced the A and B solenoids. This improved my situation, allowing me to drive in 3rd gear with O/D off up to 50 mph, at which point I would get the racing/slamming behavior. With O/D on, I would get those bad behaviors anywhere in 3rd/4th range.

I concluded I had a problem with torque converter clutch operations. I found that there was an open in the harness, pin 8 on tranny side to pin 1 on PCM side. I found and fixed a broken wire in the harness between C439 and C96 (easily accessible!!). I also found and fixed another wire in that same stretch that was damaged but unbroken.

After that TCC operations seemed OK, but I had no 1st gear in D or Manual, reverse engagement is harsh, and downshift to 2nd at no throttle is also harsh and delayed as well. I had none of those problems before. And I was getting 4 codes! P0750, P0755, P0760 and P0765 indicating 4 solenoid problems!

The only problem I'm able to find in all the pinpoint tests I'm able to run (A5-A8, A10-A14 and B3-B10) is that problem with pin 4 in the B5 test.

(Needless to say I don't have a Ford WDS or IDS tester and can't run the tests that require those.)

But based on your advice above, I cleared codes and started just to idle three times. At this point I get just P0750.

So I plan to go for a drive shortly to see if any other codes recur, but things aren't adding up very well for me, and I'm wondering if someone with more expertise can see through the haze.

By the way, this 2002 has just 80,000 miles on it, so based on your information above, it would seem that the direct clutch is not a prime suspect.
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Old 09-06-2011, 04:42 PM   #5
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After a short city drive (~ 5 miles), P0760 and P0765 have been added back as Pending codes. This in addition to P0750 which returned as a full code right away after 3 starts to idle.

If the previous situation repeats, P0755 will return as well. The 4 codes would then be reporting "solenoid circuit failure" for A, B, C and D.
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Old 09-07-2011, 10:30 PM   #6
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Here's all I can tell you. If you did a wiring repair and now you have more problems then before, that's a problem. I can give you the pcm pin #'s and the 9 pin bulkhead connector on the front of the trans. When you check the wiring for continuity, also check that there is now resistance to ground. Also make sure none of the wires are shorted together. Continuity = less than 5 ohms. Open circuts are over 10,000 ohms. Pin 81 bk/rd to trans pin 7. Pcm pin44gn/og to trans pin 2. Pcm pin 1 GN/BL to trans pin 8. Pcm pin 73 GN/YL to trans pin 6. Pcm pin 102GN/WT to trans pin 1. pcm pin 99GN/OG to trans pin 9.Pcm pin 82GN/BL to trans pin 3. Don't worry about trans pin 4 and 5 because they are the tft signal and return. Pin 7 BK/RD should be your 12 volt source to feed the shift soleniods. Check that with the pcm plugged in and key on. All the green wires with different color tyracers are the ground drivers to turn on the individual solenoids. between the pcm and the trans is one connector, C96. It's a 16 pin connector. Recheck your previous wiring repair. You did something wrong if you have more codes than when you started. There is also a wiring harness inside trans also. hope this helps.
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Old 01-19-2013, 10:20 AM   #7
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How did you, or were you able to fix your situation? I am having the same symptoms and a P0755 code only. I replaced all six solenoids about 6 weeks before this new problem began. At that time I only had a P0761 Solenoid C "stuck off" code with lurching from 1st to 2nd gear and frequently no O/D. That problem was rectified. I have heard from tranny shops that 4f27e codes are sometimes generated erroneously when the tranny is just breaking down. Should I believe them and go ahead with a $2000 rebuild? What did you end up doing? I am not going to do all the pin testing you did. This vehicle is just for backup around town, if that matters. Thanks in advance.
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Old 01-19-2013, 10:31 AM   #8
JD_Hupp
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Sorry, I never did solve that problem -- had to put it on hold till I got through some other projects!
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Old 01-20-2013, 01:04 PM   #9
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Thanks anyway. Do you still have the car?
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Old 01-20-2013, 01:12 PM   #10
JD_Hupp
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I do, and expect to get back to troubleshooting it eventually. Currently I suspect that it's another short or open somewhere.
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