Any fault that puts you in full limp-in should also light the CEL.
If it's in 3rd gear only with no CEL, then you might have lost the main 12V power feed to the trans (from the trans relay in the PDC/TIPM). Although I'd expect even that to light the CEL.
yup, I noticed that before work, was going to ask you about that.....anyways, I checked the fuse (#4, 15 amp), it was good....both speed sensors had ~530ohms and the CEL did come on....P0731....I didn't reset the code or drive it.....
If you start it up fresh, shift into Drive, and take off gently, do you get any first gear at all?
If you do the same thing, but instead of Drive you tap it down to manual "1", do you then get first gear?
Do you have a scan tool that can read input (turbine) and output speeds? If so, then if you restart it, and shift into Drive at a dead stop (brakes applied), do both speeds read zero? If you then take off, do both speeds increase, or does one stay at zero?
Simply restarting it (make sure to turn key to the full LOCK position first) should clear any active fault condition. You don't have to clear the fault or reset the CEL. Trans should operate normally after each restart, until it detects another fault.
well interesting stuff, i started the truck & test drove. Everything acted normal....took off and accelerated normal...shifted normal...went into O/D as normal. No CEL...checked for stored or pending codes...nothing....drove to work...around 25 miles...about 18 of it highway going 70-75mph/2k-2100rpms...35"tires/4.56gears....
Then my guess would be you have an intermittent electrical problem somewhere. You'll likely have to wait til it happens again to troubleshoot it.
But there is one other option. Whenever a transmission fault is set, the PCM stores a block of data (called DTC Event Data) that shows exactly what was happening when the fault set. It records engine RPM, turbine RPM, output RPM, line pressure, desired line pressure, current gear, target gear, solenoid states, pressure switch states, etc. Dealers can read this data with a scan tool (even if the fault has been cleared), as long as the PCM has not been flashed or quicklearned. The PCM will store up to 6 banks of DTC Event Data. See if you can have a dealer or shop read the DTC Event Data for your P0731 fault, and print out the results for you. Then post those results here. That could tell us what's going on.
damn good info to know! thx, ill do that....don't know exactly when tho….only thing i could think of when i plugged the sensors back in, maybe it lost contact for bit and unplugging/plugging back in, corrected it. They were in solid before tho...not dirty or anything....thx very much for your time in replying to this issue!!
I have a similar problem with my 2009 dodge durango it has the same 545RFE transmission. When the transmission gets hot the shifts from 2nd to 3rd become harsh it makes a clunk noise, I recently replaced the transmission filter and changed the fluid and still has the issue. I should also note it has been like that for the last 10,000-20,000 miles and when I replaced the fluid the old fluid wasn't that bad and has life on it, but I thought this will help.
Well, then I would suspect you have a leak somewhere in the OD clutch hydraulic circuit. Could be a small tear in a piston seal, or could be a worn valve (or bore) in the valve body. My guess is that as the trans warms up, the fluid gets thinner (thereby leaking more). The shifts are calibrated and the PCM knows how long it should take the OD clutch to apply. The 2-3 shift is a handoff between the 2C and OD clutches (2C releases as OD applies). Basically, the PCM will turn on pressure to the OD clutch, and then (when it thinks that clutch should be almost applied) it releases the 2C clutch. Normally, the OD clutch has enough capacity at that point to complete the shift.
But if there's an unexpected leak, it takes longer for the OD clutch to gain capacity when its pressure feed is enabled. So the PCM tries to run the shift as usual, but when it releases the 2C clutch, OD hasn't applied yet, so the trans basically goes into neutral and the engine RPM starts to rise. The PCM will detect this, and will momentarily reapply the 2C clutch to prevent engine runaway. It will then release 2C again and see if the shift completes normally. If the engine RPM starts rising again, the PCM will again briefly reapply 2C, and the cycle repeats. You feel a shudder during the shift as the 2C gets dithered on and off rapidly. There is time limit for the shift to complete, after which the PCM simply applies the OD clutch full bore (with full line pressure; it normally uses a reduced, ramped pressure during the upshift to give a smooth shift), so the OD clutch bangs on hard and you get the bump / clunk.
So if the relearn doesn't help, then a leak from the OD passage is likely. In that case, I would try a new valve body first (since you can replace that without pulling the trans), and while the VB is out I would air check the OD clutch passage in the case to see there is obvious leakage from that passage. The clutches all have a small bleed orifice, so some leakage is normal, but I would compare OD to UD and see if they are similar. If OD seems "leakier," then you may have to yank the trans and replace the OD clutch seals.