P1784 Lr Pressure Switch Sense Circuit Test: 2Nd Opinion Needed

[vvv]

I had a P1784 on our Grand Voyager earlier in the year and I installed a new Mopar solenoid pack, input and output speed sensors, filter and ATF+4 and all seemed OK... for a while at least. After about 500 miles the code was back again but intermittent. After 1000 miles I noticed that fluid was weeping from the bottom of the transfer gear cover. The car hasn't been used for a while and I finally had time to have another go at it this week.

 

I removed the gear cover cover and let it drain off overnight.

I cleaned and degreased the gasket faces properly but noticed that the corroded outer face of the cover seemed to stay oily.

Reassembled using Permatex Auto Trans RTV hand tight for an hour, then torqued to 20Nm and left for 24 hrs before refilling ATF+4. All going well so far.

 

Refilled the transmission checking the level when idling in park and getting filling it to cold level high mark. Pulled away and it seemed great up the hill from home but P1784 back again.

 

So now today I have gone through the wiring checks in the FSM and this is what I have for the test results.

 

Test 6:

Remove Transmission Control relay, Fit jumper wire to connect socket for relay pin 30 and 87.

With a 12v test lamp connected to -ve terminal on battery, connected lamp to Pin 4 in Solenoid harness.

Result=Lamp glows very brightly, proceed to Test 7.

 

Test 7:

Jumper wire removed, relay reinstalled.

Ignition off.

Measure resistance between Pin 50 in TCM harness and Pin 2 in Solenoid harness.

Result=Nothing! Appears to be open circuit. Repeated using another digital multimeter, same result.

Value displayed is technically less than 5.0 Ohms. Proceed to Test 8?

 

Test 8:

Measure resistance between ground and Pin 2 in Solenoid harness.

Result=Nothing! Appears to be open circuit. Repeated using another digital multimeter, same result.

Value displayed is technically less than 5.0 Ohms. Do I treat this as a short to ground?

 

Test 9:

Remove Transmission Control relay, Fit jumper wire to connect socket for relay pin 30 and 87.

Ignition on, engine not running.

Measure voltage between Pin 50 in TCM harness and ground.

Result=0.02v

Value displayed is less than 0.5v, Proceed to Test 10.

 

Test 10:

Replace TCM - Not done this yet.

 

So I need a second opinion.

Do I have a short to ground or is my TCM bad?

 

Oh, nearly forgot, I think the transfer gear cover has a pin hole in it. A small amount of weeping visible from the cover surface after fully degreasing the outer face.

Edited July 16, 2015 by vvv