Here are the codes you pulled awhile back:
P0841 - Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance
P0871 - Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance
P0872 - Transmission Fluid Pressure Sensor/Switch "C" Circuit Low
P0700 - Transmission Control System (MIL Request)
P0650 - Malfunction Indicator Lamp Circuit Conditions (Key on or engine running, system voltage from 8-16v, then the PCM detected an improper voltage level on the ODM 'D' output 1 circuit, condition met for at least 30 seconds.)
U1000 - Class 2 Communication Malfunction Conditions
P0381 - Glow Plug/Heater Indicator Circuit
P0530 - A/C Refrigerant Pressure Sensor "A" Circuit
U2106 - Loss of Communication with Transmission Control System
Since the transmission, glow plugs, and a/c refrigerant sensors are on different harnesses I think you might need to look beyond the trans harness and TCM. Have you checked your ECM connectors? All grounds? Including the ones inside the truck under the dash? The cluster acting up and changing brightness makes me think it might be a loose ground inside. There are grounds under the dash pad near the lower left and right corners of the windshield. The driver's side ground is for the cluster and dash harness, and I believe the passenger side one is for the HVAC unit.
You mentioned that you had pulled and reinstalled the large connectors under the fuse box correct? Got the bolts re-tightened on those? There's a couple of large connectors under the dash to check as well, same style with the bolt that holds them together. Since it sounds like you have access to another truck, have you tried swapping ECMs as well, or just TCMs?
I'm not 100% sure on the 03+ trucks, but on the 99-02s there is a class 2 data bus block under the dash too where the comms wires from several different modules connect so they can all communicate with each other. Might be worth looking into on yours as well.
Anyway, my guess is a bad/broken ground wire or class 2 data wire.
P0841 - Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance
P0871 - Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance
P0872 - Transmission Fluid Pressure Sensor/Switch "C" Circuit Low
P0700 - Transmission Control System (MIL Request)
P0650 - Malfunction Indicator Lamp Circuit Conditions (Key on or engine running, system voltage from 8-16v, then the PCM detected an improper voltage level on the ODM 'D' output 1 circuit, condition met for at least 30 seconds.)
U1000 - Class 2 Communication Malfunction Conditions
P0381 - Glow Plug/Heater Indicator Circuit
P0530 - A/C Refrigerant Pressure Sensor "A" Circuit
U2106 - Loss of Communication with Transmission Control System
Since the transmission, glow plugs, and a/c refrigerant sensors are on different harnesses I think you might need to look beyond the trans harness and TCM. Have you checked your ECM connectors? All grounds? Including the ones inside the truck under the dash? The cluster acting up and changing brightness makes me think it might be a loose ground inside. There are grounds under the dash pad near the lower left and right corners of the windshield. The driver's side ground is for the cluster and dash harness, and I believe the passenger side one is for the HVAC unit.
You mentioned that you had pulled and reinstalled the large connectors under the fuse box correct? Got the bolts re-tightened on those? There's a couple of large connectors under the dash to check as well, same style with the bolt that holds them together. Since it sounds like you have access to another truck, have you tried swapping ECMs as well, or just TCMs?
I'm not 100% sure on the 03+ trucks, but on the 99-02s there is a class 2 data bus block under the dash too where the comms wires from several different modules connect so they can all communicate with each other. Might be worth looking into on yours as well.
Anyway, my guess is a bad/broken ground wire or class 2 data wire.
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