5-speed auto major problem, help please..

[hemibadger]

A plea for help from Scotland, UK. Apologies if this is in the wrong place, but I didn't see a specific sub-forum that it fitted...

Dodge Ram 2500, early 2004, 5.7 Hemi with 545RFE autobox and NGC controller.

So... about 4 years back my auto trans wore out. It was replaced with a remanufactured unit, shipped to the UK from the USA, and fitted by myself. I had an initial solenoid pack pressure switch fault which was repaired under warranty (new solenoid pack sent, I fitted it myself) and it's been perfect ever since.

3 weeks ago, I noticed a misfire and could hear HT "arcing" somewhere near no.3 cylinder's coil pack. Not wanting to go in there twice, I elected to just replace all 16 plugs, all 8 coil packs and all HT leads. Yesterday, I finished the job and the engine now runs smoother than ever - but I have a new, major problem.....

It drove up a fairly steep slope to the workshop door just fine 2 weeks ago, but today the trans is in limp mode, with no MIL lamp on! We've had some heavy rain this last week, but all ecu's and electrics are dry.

I have DRBIII scantool, so I had a play this morning.
One-trip fault, P0755, 2C solenoid circuit. (It will clear, but comes back as soon as Drive, 2 or 1 is selected with the engine running, fault does not re-appear when selecting P, R, or N from startup).
Unable to carry out solenoid function test due to Limp-Mode.
I've checked the electrical connections at the gearbox and NGC control module (ECU), and I'm measuring 1.7 ohms across the 2C solenoid at both the gearbox connector and the harness plug at the ECU, which is pretty much in the middle of the values I've found online of 1.3 and 1.9 ohms, so I can't see the fault being in the gearbox or wiring....
Am I looking at an ECU internal failure here? Anyone have any ideas or pointers that may help me? Please?

 

[yoda]

Vehicle Issue Alternate diagnosis for Solenoid Circuit DTCs P0750 P0755 P0760 P0765 P0770 P2706 - 45RFE 545RFE 68RFE trans;Verify that vehicle has a solenoid circuit fault (DTC P0750, P0755, P0760, P0765, P0770, or P2706). Check whether the fault can be reset: (1) With engine idling in Park for several minutes, or (2) during a test drive. If the fault will not reset, this procedure will not be useful.

System or Component No Shift / Will not Shift Up or Down;DTC / Error Message;Group 08 - Electrical,Wiring,Connector,Harness,Group 21 - Transmission / Transfer Case / Power Transfer Unit ( AWD ),Automatic Transmission / Transaxle,Valvebody Assembly,Solenoid / Sensor;Yes - Intermittent,Yes - Continuously

Recommendation Possible Causes: Wiring open circuit Wiring short to ground Wiring short to another circuit Trans controller Trans solenoid module These DTCs are strictly electrical. The trans controller runs a continuity check on each solenoid circuit periodically (normally, every 10 seconds). Each inactive solenoid is turned on for a few milliseconds, then off. Each active solenoid is turned off for a few milliseconds, then back on. When each solenoid is turned off, the collapse of the magnetic field around the coil creates a voltage spike in the solenoid wire, which can be sensed by the trans controller. If the inductive voltage spike is not sensed by the controller, the solenoid is tested again. If the test fails three consecutive times, the appropriate DTC is set. If the solenoid continuity check is run in response to a gear ratio or pressure switch error, one failure will cause the DTC to set. These DTCs normally indicate a problem (open circuit, short to ground, or short to voltage) with the wiring or the solenoid coil. However, it is also possible for the solenoid driver chip (in the trans controller) to fail, so that it fails to recognize the inductive voltage spike (and sets the DTC even though the wiring and solenoid are in fact OK). Therefore, diagnosing these DTCs can be challenging. The following is an alternative method for diagnosing these DTCs, which is useful if the DTC is a hard fault and is easily repeated: 1) First, we can check for a bad wire or connector terminal: Swap the suspect solenoid circuit wire (at BOTH ENDS of the harness) with any other solenoid wire EXCEPT LR (swap with the 2C, 4C, UD, OD, or MS solenoid wire). For example, if the DTC is P0765 (UD Solenoid Circuit), swap the UD solenoid wire (at BOTH the TCM connector AND the 23-way solenoid connector at the transmission) with one of the other solenoid wires (such as the 2C solenoid wire). If the DTC was P0750 (LR Solenoid Circuit), swap the LR solenoid wire with one of the others. Refer to the Service Information to find the correct pin numbers to swap. Operate the vehicle until a Solenoid Circuit DTC sets. Did the SAME DTC (as originally set) reoccur? Yes >> Problem is in either the solenoid or the controller. Go to 2. No, DTC for the SWAPPED solenoid set >> Problem is in the wire (or terminals) that was swapped. Repair as required. If hardwiring the circuit, completely replace the suspect wire and disconnect or remove the old wire. Do not merely add a new wire in parallel with the old one (if the old wire is shorted to ground or to another circuit, you will still have a problem). 2) Clear the DTC and check whether the fault will reset with the vehicle idling in Park. Will the DTC reset while idling in Park? Yes >> Go to 3. No >> This procedure cannot determine whether the controller or solenoid is the failed part. Swap the solenoid wires back to their original positions.Refer to the published diagnostic procedure (for the original DTC) in the Service Information. For 2004 MY and prior vehicles, use the procedure for the current model year (545RFE transmission) but refer to the older MY information for the correct wiring pinouts. Connect the Transmission Simulator tool and run the solenoid actuator test (using the scan tool) for 2 minutes (or however long it normally takes for the DTC to reset), as described in the diagnostic Service Information.If the Simulator test fails, replace the trans controller. If the Simulator test passes, replace the solenoid. 3) Is the DTC P0750 (LR Solenoid Circuit)? Yes >> The other solenoid circuit DTCs (P0755, P0760, P0765, P0770, and P2706) can be diagnosed using step 4 below. Unfortunately, this particular DTC (P0750) presents a unique problem, so that step 4 cannot be used. In Park (or Neutral), the LR solenoid is applied and the LR pressure switch is closed. All other pressure switches should be open in Park/Neutral. If the procedure in step 4 were used (swapping the LR wire with another at one end only), the LR pressure switch would not be closed, causing an LR pressure switch DTC. For a P0750 DTC, go back to step 2 above and follow the procedure for the "No" choice. No >> Go to 4. 4) Swap the two solenoid wires (which you swapped at BOTH ends in step 1 above) back at ONE END ONLY. This will mean the two wires are swapped at one end, but are in their original positions at the other end. Therefore, the "bad" (or suspect) driver in the TCM will be operating a "good" solenoid coil, and a "good" driver in the TCM will be connected to the "bad" (suspect) solenoid coil. Clear any DTCs. Start the engine and let it idle in Park until a solenoid circuit DTC is set. Stop the engine and read the DTC. Did the SAME DTC (which was set originally) reset? Yes >> The driver chip in the TCM is bad. Replace the TCM. Swap the other end of the wires back so that all wires are in their original position. No, a different Solenoid Circuit DTC set >> The coil in the solenoid is bad. Replace the solenoid module. Swap the other end of the wires back so that all wires are in their original position

 

[hemibadger]

Thanks for the fast reply Yoda, I still have to check the 2C solenoid wires for any shorts to other wires or earth, with both the TCM and transmission case connectors unplugged. All I've done is connector cleanliness checks and basic solenoid resistance, plus a play with the DRBIII tool.
What is interesting is the description of how the TCM checks the solenoids by creating the power spike every 10 seconds - if it takes 3 incorrect responses to register the fault and put the trans into limp mode, it's even more confusing that mine throws the code and goes into limp as soon as D is selected, even passing through D to 2 or 1....
I can sit at idle in P, R or N with no fault code - it's only as soon as it shifts into D.

 

[hemibadger]

Update. All wiring checked for continuity, shorts, high resistances to earth, other wires and power feeds. I decided to try and ***** in another solenoid pack and see what happened.... apart from all sorts of TRS and pressure switch faults, which were to be expected really, the findings were inconclusive. I drained the trans, removed the valve body and replaced the solenoid assembly with a replacement sourced through Rock Auto. New solenoid pack installed and oil back in, and I still got the exact same 2C Solenoid fault code!
I removed the 2C and 4C Solenoid wires from the multiplug at the Powertrain ECU and swapped them, so that the ECU would now be checking the 4C solenoid when it thought it was checking the 2C.... guess what, exact same, still showing a 2C fault code, which pretty much proves it's an internal fault within the ECU!
I have now messaged an ECU "specialist" in the USA twice, with regard to an advert they have on eBay for the correct part number Powertrain ECU that I need, but they haven't bothered to respond to me! Great, back to square one trying to find an ECU, why would I want to deal with a company that can't even be bothered to respond to a sales query....!

 

[yoda]

Glad you were able to figure it out.
Do you not have any Dealer support over there?

 

[Fast69Mopar]

Check out Auto ECM Electronics in Grand Prairie, TX.

+1 972-988-9922

I've done some business with them in the past and had good results. They may be able to assist. Good luck.

 

[hemibadger]

Hi Yoda, sadly not. The ONLY Chrysler dealers in the UK that MAY have had technicians trained on the Ram were individual dealerships that took on the SRT-10 model, as that was the only official UK imported Ram ever sold here, anything else is a personal import. Because Daimler-Chrysler vanished after the parting of the ways between Mercedes and Chrysler, the dealerships are now all part of the Fiat group, with zero Ram experience. Add to that, the fact that most Tech's in the UK will move from one dealership to another as and when they get a better salary offer, it is rare to find a dealers that has technicians who have been there long enough to really know the products inside-out.....