Transmission code P0740

Tiny
COMPMANS
  • MEMBER
  • 2001 JEEP GRAND CHEROKEE
  • 4.0L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 166,000 MILES
Bought this vehicle two months ago with no codes active or stored. I drove the car for a week or two and noticed at high speeds the car would downshift hard when I let go of the gas. This does not happen every time in the two months I’ve owned the car it has only happened twice. One day I start the car up take it to the corner store and when it comes to a complete stop the engine stalls out. I turn the car back on and it works fine. A week later the same thing happens followed by the p0740 code. I took the vehicle to Aamco who told me the whole transmission needed to be replaced $2,500.00. I stuck a bottle of Lucas oil transmission fix in and the car stopped stalling. I did get the code again after clearing but no dramatic downshift or stall this time it just popped up at random one day. I took the car to a local transmission shop. He hooked his scan tool up and took it for a couple drives and found no issues. I wanted to believe the guy but there was a language barrier so I took it to another local transmission shop and the guy wouldn’t even do a diagnosis. Told me that from what I’m describing the torque converter is failing for sure and the converter needs to be replaced and transmission rebuilt $2,300.00. I guess my overall question is, could this be a simple TCC solenoid gone bad, electrical issue, oil pressure inside the transmission or are these guys right and the whole transmission needs to be rebuilt? It works fine now with the Lucas oil in but I drive this thing on the highway and the last thing I want is it stalling doing 75+mph. Thanks for the advice in advance.
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Monday, June 8th, 2020 AT 6:35 AM

5 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The problem "Could be an internal transmission issue" but since it happened all at once, it is likely related to a wiring issue. Here is a list of things that can cause the problems.

Possible causes:

TPS DTC p0122 present in the TCM
TPS DTC's present in the PCM
TCM DTC's p1748 and/or p1749 present
Intermittent wiring and/or connectors
Transmission oil burnt and/or contains excessive debris
Internal transmission

Are any of the other codes present?

As far as the stalling issue, it is likely because the TCC isn't releasing. It shouldn't cause the vehicle to stall when moving.

Let me know.
Joe
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Monday, June 8th, 2020 AT 7:12 AM
Tiny
COMPMANS
  • MEMBER
Only other codes were for the EVAP system. P0456 and P0442. I replaced the gas cap waiting to see if the codes pop back up now. I know the previous Owner changed the transmission fluid and I m assuming it was leaking as he replaced the gasket as well. Should I leave the electrical diagnosis to a professional or is it something I should be able to locate?
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Monday, June 8th, 2020 AT 7:28 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I'm not sure what you are comfortable with. However, here are the diagnostics. Keep in mind, it could be solenoid C in the transmission which is replaceable.

_______________________

Here are the diagnostics, The attached pics are the actual directions.

2001 Jeep Truck Cherokee 2WD LHD L6-4.0L VIN S
Transmission Code
Vehicle ALL Diagnostic Trouble Codes ( DTC ) Testing and Inspection P Code Charts P0740 Transmission Code
TRANSMISSION CODE

pic 1

pic 2

pic 3

P0740 - SOLENOID C FUNCTIONAL FAULT

When Monitored and Set Condition:
P0740 - SOLENOID C FUNCTIONAL FAULT

When Monitored: Continuously with Solenoid C (TCC) energized.

Set Condition: When the solenoid is energized and the Engine RPM does not equal the Transmission's Input Speed RPM or when the solenoid is de-energized and the Engine RPM equals Transmission input RPM.
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Monday, June 8th, 2020 AT 7:36 AM
Tiny
COMPMANS
  • MEMBER
Awesome, thank you for that. Since the Lucas oil has kept the transmission from stalling the engine should I change the fluid? I feel like the Lucas oil is a bandage that s going to keep me from getting to the root cause. What do you think? Also, where can I download or purchase the proper wiring diagram for my vehicle?
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Monday, June 8th, 2020 AT 7:59 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Honestly, if the fluid is still clean, I would likely leave it alone. As far as a wiring schematic, I attached three pics below that are for the transmission circuits. I had to break it into three pics to make them readable, but I did overlap so you could follow them.

Let me know if that is what you needed.

Joe
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Monday, June 8th, 2020 AT 7:32 PM

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