4L80E error code 73 - trans light always on

Hi there.
My 1988 Humvee M1097A2 (rebuilt by Army on 2013) with a 4L80E transmission and a 6.5L NA has the trans light always on as soon as the ignition is turned on and goes out after the ignition is turned off only.
I followed the DVOM procedures to check the error code 73 and realized that the pressure solenoid was with the resistance out of range (6.7 ohms). I replace de solenoid and also the internal harness, as the trans conector was full of oil. The oil is at the correct level as well.
The truck runs great and all the gears shifts perfectly, even before the PCS and internal harness replacement.
Anyone had this issue? Any idea how to solve this?
Thanks!

So now all codes are gone?

Unfortunately not. The code 73 is still present, even with the new internal harness and PCS installed.

My guess,
Check to make sure the engine RPM senor in the timing cover is hooked up so the TCM knows that the engine has started and to turn out the light. Without engine RPM the torque converter lock up will not work but you will have all 4 gears it will just feel sluggish. The original plug in the harness for rpm should be a 2 pin connector under the dog house on the drivers side sticking out of the main harness about the same level as the oil pressure sender on the engine. The sensor will be in the front timing cover on the drivers side just above the oil pan. I have seen times when they do a swap they don't bother to extend the wires in the harness to reach the new position of the RPM sensor.

Just takes a quick look, my best guess from this description.

Edit: Just saw you don't have a turbo engine, so the connector should be sticking out of the main harness about the same level as your heater temp controls.

Just check the connectors and they are plugged.

Supplement 7 sez:

DTC 73 will set when return amperage varies greater then .16 amps from commanded amperage.

ME: The amps sent by the TCM can vary from 0.1 to 1.1 amps. The amps in the return wire are out of spec. You must figure out why.

Supplement 7 sez:

Diagnostic aids: Check for poor connections at TCM and at transmission connector.

ME: check the harness between TCM and 4L80E for worn through insulation short circuits.

Yes, I read the supplement, but the problem is how to identify the issue. Perhaps I need to find a specialist to check the wires. Anyways, thanks for the tips and valuable help. When the problem is solved, I’ll post here with de outcomes.
Just one additional comment. I noted a different behavior of the trans light when the engine is warm. I turned on the ignition, the trans light comes on. When I push engine start, the light goes out for 2 or 3 seconds and comes on again. This only happens when engine is warm. At cold starts, the light is always on after the ignition is turned on.

Did you read this thread?

Not yet, will do. Thanks!

Trans lamp on while engine running is the TCM not seeing the engine running, replace the CPS, if that doesn’t do it? The TCM is bad.
just had both these issues on separate trucks in the shop.

Error. Please delete

Retiredwarhorses said:

Trans lamp on while engine running is the TCM not seeing the engine running, replace the CPS, if that doesn’t do it? The TCM is bad.
just had both these issues on separate trucks in the shop.

Click to expand...

Thanks! What is CPS and where it is located please?

Crank position sensor (CPS), front timing cover - drivers side - just above the oil pan. used for engine RPM to the Transmission control module (TCM) uses 2 pin connector.

REF said:

Crank position sensor (CPS), front timing cover - drivers side - just above the oil pan. used for engine RPM to the Transmission control module (TCM) uses 2 pin connector.

Click to expand...

Thanks again!