So here's the deal.
Bought this truck with a bad trans, rebuilt it (with help from member here) with some better parts and it's been working great for the last 5 years and 22k miles.
A while back I was getting a random check engine light and limp mode, it would come and go so I decided to dig into it and after a couple hours of testing using Identifix/ Mitchell testing procedures for the code I had (P0753) I came up with a bad PCM. replaced it had it re-flashed for my vin and accy at the dealer and drove it for about a month with no problems then it started coming back.
Decided to go ahead ahead and service the trans and installed all new electronics while there so everything in the trans is new and adjusted the bands as well and replaced the trans pigtail.
Now it is an instant limp/ check engine light upon the 3-4 shift, driving with OD off it's fine.
I'm about to drive this into something really solid at this point so before I commit Ins fraud I decided I would ask for help here
Last night I looked in the Trans part of the PCM and found a Generator field code so I spent a couple hours following that around, it all checked good.
Currently however all I have is the P0753, it does not show as pending or current unless I turn off the OD switch and left it attempt to shift in to 4th.
Code Description: P0753 - Trans 3-4 Shift Solenoid / Trans Relay Circuits
Functional Operation; 4th gear operation is provided electrically through the OD solenoid. The voltage in the OD Solenoid control circuit is monitored by the PCM whenever the key is on. If the actual circuit voltage is different than the expected voltage, code P0753 will set.
Possible Causes;
# Failed Transmission Control Relay
# Failed OD Solenoid
# Open or shorted OD Solenoid control circuit
# Open or shorted Trans Control Relay output circuit
# Open or shorted Fused B+ circuit
# PCM - Internal failure
DIAGNOSTIC ROUTINES
1. Be sure to perform the Preliminary Tests
2. If any of the following codes are present, diagnose them first; P1765
3. Disconnect the solenoid connector at the transmission and check for the presence of battery voltage at pin #1 with the engine running. If there is no voltage present, perform test P1765.
4. If codes P0743, P0748 and P0753 are all present, and you have 12 volts at pin # 1 of the solenoid connector, replace the TCC / OD solenoid assembly.
5. Disconnect the solenoid connector at the transmission to test the OD Solenoid. Connect an ohmmeter across pin# 6 and pin# 1 of the solenoid connector on the transmission side. The resistance should be between 25 & 60 ohms. If not, replace the TCC / OD Solenoid assembly.
6. Measure the resistance between pin# 6 of the solenoid connector (transmission side) and a good ground. If you have less than 5 ohms, replace the TCC / OD Solenoid assembly.
7. Disconnect the solenoid connector at the transmission to test the internal wiring. Make sure that your Governor Solenoid connector (inside the pan) is plugged in if you disconnected it in the previous step. Connect an ohmmeter across the pins of the solenoid connector on the transmission side. Resistance values should be as follows;
* Between pin# 6 and pin# 2 = above 100K ohms
* Between pin# 6 and pin# 3 = above 100K ohms
* Between pin# 6 and pin# 4 = above 100K ohms
* Between pin# 6 and pin# 5 = 28 - 68 ohms
* Between pin# 6 and pin# 7 = 50 - 120 ohms
* Between pin# 6 and pin# 8 = above 100K ohms
If any of the resistance values (above) are not within specs, replace the TCC / OD solenoid assembly.
8. Check the integrity of the OD Solenoid control circuit from the PCM connector to the transmission solenoid connector.
9. Check the OD Solenoid control circuit for a short to ground.
10. Check the OD Solenoid control circuit for a short to voltage.
11. Check the integrity of the Trans Control Relay output circuit from the Trans Control Relay connector to the solenoid connector.
12. Check the Trans Control Relay output circuit for a short to ground.
13. Disconnect all three PCM connectors. Disconnect the solenoid connector at the transmission and measure the resistance across pin# 6 and every other pin in the connector. Each pin should measure over 100K ohms. If you have under 100K ohms between pin# 6 and any other circuit in the connector, repair the wiring harness for wiring shorted together.
14. If all other possible causes have been eliminated, replace the Powertrain Control Module (PCM).
Been there/ done that tested good but as I posted I replaced everything electronic in side it anyway to eliminate the possibility of an intermittent failed part plus I replaced the pigtail at the trans.
Previously using Identifix testing procedures I diagnosed a bad PCM, replaced it. Had the same problem so I replaced it again (so 2 new PCM's now). problem persists.
Now the code is instant instead of random so I made something mad.
I've tested the harness between the PCM and trans looking for a break in a wire somewhere/ nope.
Tested resistance on everything as directed via Mitchel and the factory repair manual. Nothing.
Tested and replaced the Trans relay.
If I go through all these tests I still come up with the conclusion the PCM is bad but how can I get 3 bad PCM's? 4 if you count the original PCM also.
That is what I figured. The computer is seeing a problem with the wiring some where (tripping the code) and is killing the power to the relay turning off the relay and taking your 12 volts away from the transmission. You have a wiring problem some where.
This does bug me also though" Last night I looked in the Trans part of the PCM and found a Generator field code so I spent a couple hours following that around, it all checked good." Some where I remember reading that the alternator can cause the relay to not be activated, let me do some checking today.
The reading I did showed it needs 10v in that circuit to keep the relay working. At idle it has about 8.7v then anything above idle it goes to 10.5-11v but I dont have a way to monitor that field when driving to see if the voltage drove or not.
At this point I have it parked it in a dark corner of the shop.
The light continues to randomly pop up.
I have ran new wires from the ECM to the Trans relay for not only the control but power and ground are ran new as well. The only OE wire left is the one going directly to the trans.
Dont forget I have replaced the pigtail with a new OE pigtail already.
But for now as far as my Durango is concerned its staying in the corner until either I see fit to spend more time on it OR I hack out the stock axles and toss in some new Dana 60's and make it a crawler.
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