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PO740 Pending

racin_ny

NAXJA Forum User
Location
Elba, NY
I have a PO740 pending code. If I clear codes or disconnect the battery it comes back in immediately even if I don't drive anywhere. The Torque converter acts normal. Seems like it might be a sensor issue. I have already changed out the NSS. Has anyone seen this error act like this?
1999 XJ
4.0 Liter
Auto
 
A quick description of the code:

Torque Converter Clutch (TCC) unlocked for 10 sec., ECM commands converter lock-up and did not record engine speed drop.

The torque converter clutch solenoid valve is activated, with the gear in D4, by the Transmission Control Module (TCM) in response to signals sent from the vehicle speed and the Engine Control Module (ECM). Lock-up piston operation will then be controlled. When the torque converter clutch solenoid valve is activated, the torque converter lockup clutch will engage creating a 1 to 1 RPM ratio between the transmission input shaft and the rotational speed of the torque converter.

Lock-up operation, however, is prohibited when A/T fluid temperature is too low.

When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up.

Possible causes:
- Low transmission fluid level
- Dirty transmission fluid
- Faulty torque converter clutch solenoid valve
- Torque converter clutch solenoid valve harness is open or shorted
- Torque converter clutch solenoid valve circuit poor electrical connection

If I had to guess to the most likely culprit, I would look closely at the TCC solenoid.
 
A quick description of the code:

Torque Converter Clutch (TCC) unlocked for 10 sec., ECM commands converter lock-up and did not record engine speed drop.


OGauge What instrument does it get engine speed from? The tach works but does it use something else for the engine speed signal?



Thanks
 
Trans error codes are stored in the TCU... using non high end OBD-II will not be able to erase the codes once they become present. I have been unable to clear them, despite trying numerous methods, other than waiting them out with the number of engine starts. Check the level and status of your trans fluid first... proceed from there.
 
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