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Discussion Starter · #1 · (Edited)
Hello All,
04 T&C 3.8 231k
Got a p0700 and p0755 code and sure enough, the 2-4 solenoid was reading 45m ohms instead of 1.5. So I replaced the solenoid pack today, cleared all the codes and hit the road. Still in limp mode with a p0870 code O/D pressure switch circuit. I checked the solenoid pack, switch is open and without the transmission simulator I know no way to test if it's stuck open or working properly. I tested the wiring from the solenoid pack to the PCM and it's good at least all the ways I wiggled it. My only other thought is to try and disconnect just that one wire from the solenoid pack, and use a test light to see if the switch closes during the self-test during the first drive after clearing the codes.

I'm at a loss and I could use some help if anyone has any ideas, please share!

Edit: p0755 code
 

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. . . Still in limp mode with a p0870 code O/D pressure switch circuit. I checked the solenoid pack, switch is open and without the transmission simulator I know no way to test if it's stuck open or working properly. . . .
How did you test the O/D pressure switch sense circuit? If you checked for continuity to ground with the vehicle stationary and transmission in PARK or NEUTRAL, the sensed circuit will NOT have pressure (no clutch engaged) and should be open.

This is detail about code P0870 from service manual.

P0870-OD HYDRAULIC PRESSURE TEST FAILURE
When Monitored: In any forward gear with engine speed above 1000 RPM shortly after a shift and every minute thereafter. Set Condition: After a shift into a forward gear, with engine speed > 1000 RPM, the TCM momentarily turns on element pressure to the clutch ckts that don’t have pressure to identify the correct pressure sw closes. If the pressure sw does not close 2 times the code sets

LOSS OF PRIME DTC P0944 PRESENT
RELATED DTC’S PRESENT
INTERMITTENT WIRING AND CONNECTORS
TRANSMISSION CONTROL RELAY OUTPUT CIRCUIT OPEN
OD PRESSURE SWITCH SENSE CIRCUIT OPEN
OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO GROUND
OD PRESSURE SWITCH SENSE CIRCUIT SHORT TO VOLTAGE
INTERNAL TRANSMISSION
TRANSMISSION CONTROL MODULE

The 2-4 pressure sense switch is closed when the transmission shifts and runs in 2nd gear. The 3-4 / OD pressure sense switch is open. The 2-4 pressure sense switch and wiring circuit to the PCM is functioning properly; otherwise you would have code P0846 which you do not have.

The 3-4 / OD pressure sense switch is closed when the transmission shifts and runs in 3rd gear and 4th gear / OD. I would suggest you check the wiring for the 3-4 / OD pressure sense switch from the solenoid control to the PCM. Make sure pins and receptacles are clean and tight fitting. See attached image.

Transmission Control Wiring to PCM.gif
 

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Discussion Starter · #3 ·
How did you test the O/D pressure switch sense circuit? If you checked for continuity to ground with the vehicle stationary and transmission in PARK or NEUTRAL, the sensed circuit will NOT have pressure (no clutch engaged) and should be open.
I measured ~45m ohm to ground from pin 3 on the solenoid pack. I also have continuity from pin 3 in the solenoid plug to pin 22 in the PCM 38 way.

I'm thinking can I backprobe pin 3 and somehow check for the switch closing when it runs the pressure test over 1000rpm? Maybe I got a bad solenoid pack since I didn't have this problem before? (Borg Warner, Dorman branded)

The old pack definitely had an intermittent high resistance on the 2-4 coil.
 

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. . . I measured ~45m ohm to ground from pin 3 on the solenoid pack. I also have continuity from pin 3 in the solenoid plug to pin 22 in the PCM 38 way. . . . Maybe I got a bad solenoid pack since I didn't have this problem before? (Borg Warner, Dorman branded) . . .
45 m ohm means 45 milliohms?

I am thinking that with the vehicle at rest (not running) that pin 3 in the transmission pressure solenoid should show NO continuity and be open. Check pin #1 (2-4 pressure sense switch) and pin #2 (low/reverse pressure sense switch) for continuity. I think in this test scenario all pressure switches should be open. I do believe you have a failed replacement transmission solenoid pack.

Attached schematic shows the transmission circuits pressurized with fluid with the transmission in 4th gear - overdrive. Those traces are in black and it shows both the 2-4 pressure switch and 3-4 / OD pressure switch ON. With no transmission operation these switches should be open.

Transmmission Control 2_4 SW  3_4 OD SW.gif
 

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I'm thinking 45 MΩ, as in an open circuit.
I would be leery of the sol pack if it is behaving differently than before, after replacement.
An OEM part might be an important consideration here.

P0733 is a 3rd gear ratio error, not a 2-4 solenoid fault. P0700 is just the PCM telling you that a fault is present in the TCM.

What were the symptoms before servicing the sol pack? Was it going into limp-in at the 3-4 shift?
 

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Discussion Starter · #6 ·
I'm thinking 45 MΩ, as in an open circuit.
I would be leery of the sol pack if it is behaving differently than before, after replacement.
An OEM part might be an important consideration here.

P0733 is a 3rd gear ratio error, not a 2-4 solenoid fault. P0700 is just the PCM telling you that a fault is present in the TCM.

What were the symptoms before servicing the sol pack? Was it going into limp-in at the 3-4 shift?
You're right I had the wrong code it was p0755 for the 2-4.

The symptoms were this: I backed out of a parking space and when I went to forward gear, had no drive at all for a few seconds, then when it finally shifted into forward gear I was in limp mode.
Checked code and saw 0700 and 0755.
Measured 2-4 coil at high resistance (Meg-ohms)
Other coils were good.

Suppose I connect a compressed air blow gun to the O/D pressure tap, could I pressurize the switch and check if it's closing with my meter?
 

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. . .Suppose I connect a compressed air blow gun to the O/D pressure tap, could I pressurize the switch and check if it's closing with my meter? . . .
How are you testing pin #3 at the transmission solenoid pressure pack? Are you back probing pin #3 at the connector and leaving the connector attached to the transmission? Or are you removing the 8 pathway connector at the solenoid pack and touching 1 meter probe to pin #3 and the other to the transmission case?
 

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I suppose that an air test with a rubber-tipped gun into the 2-4 clutch apply port would trip the switch for diagnosis. I would regulate the air pressure down to about 50-80 psi (about the same as line pressure).
Listen for excessive air flow during the test that may mean that the 2-4 clutch seals are leaking? A heavy internal pressure leak may keep the switch from engaging and would set the fault code.
 

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I agree with IC regarding the solenoid pack - OEM or Borg-Warner. Avoid rebuilts
 

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Discussion Starter · #10 ·
Thanks all for following my saga. Shifting properly now.
What I ended up doing was using a scribe to expand the #3 pin in the pack, and now it seems to be making contact. Or maybe I have an intermittent open that I closed moving the wires. Either way, I know now that the pack works and the TCM works.
 
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