Hey all, well, i think ive narrowed the problem with repeating P0740 codes down to the solenoid being lazy. Everything providing input to the ECU as to when to lock and unlock is perfectly functioning, however, from time to time OD lockup will work, then wont, then will again, the trigger seems to be aggressive driving, but sometimes it doesnt work for no reason at all.

Should I just go ahead and replace the solenoids? The TCU doesnt really "go bad" does it?

98 XJ 4.0 with 210,000 on it.
Thanks in advance!

my OD stopped working once warm, replaced the solenoid, and fixed.

could be wiring, could be solenoids

Can't the solenoids be tested for resistance using the connector in the engine bay?

It can be tested at the TCM connector as well but the problem is that a solenoid's resistance can be good (11-15 Ohms) but have a mechanical fault, such as the solenoid pintle being sticky and not moving when the solenoid coil tries to move it. Generally when this happens you won't get a DTC because the solenoid is electrically responding.


However, For the ’98 + AW4’s, the TCM uses an Input SpeedSensor (ISS) to detect transmission solenoid functional faults (P0751 solenoidA functional fault, P0756 solenoid B functional fault, P0740 TCC solenoid Cfunctional fault).


NOTE: SINCETHE OD/CLUTCH DRUM IS STATIONARY IN 4TH GEAR OR WHEN THE VEHICLE IS INGEAR, BUT NOT MOVING. THERE WILL BE NO ISS SENSOR SIGNAL.