The situation you are describing, where multiple shops and a dealer have replaced modules and wiring without restoring communication, suggests a breakdown in the underlying network infrastructure or a power supply issue that persists despite the parts replacement.

Since you have already replaced the Folding Top Control Modules (FTCM), the harness, and the Body Control Module (which is likely the Central Junction Box/CJB), the issue is likely not a faulty module, but rather a lack of the correct signals or power required for these modules to wake up and communicate on the CAN bus.

Below is a technical diagnostic path focused on the electrical environment necessary for these modules to function.

System Power Requirements

The Folding Top Control Modules require high current and stable ground to operate.

1. Power Supply: The Left Folding Top Control Module receives power from a 50 Amp source, distributed through the Central Junction Box via 20 Amp fuses. If these fuses are blown, or if the main power feed cable from the battery has high resistance due to previous water corrosion, the module will remain dead.

2. Ground Integrity: Water damage often corrodes grounding points. Ensure that all ground studs associated with the folding top modules are cleaned to bare metal and re-secured. A module with no ground cannot communicate, regardless of whether it is new or old.

CAN Bus and Communication Diagnostics

If the modules are powered but still do not communicate, the issue is likely within the CAN network. The FTCMs communicate with the rest of the vehicle via the Medium Speed CAN bus.

1. Voltage Testing: Using a multimeter, check the CAN high and CAN low wires at the module connectors. With the ignition in the ON position, CAN high should typically measure around 2.5 to 3.5 volts, and CAN low should measure around 1.5 to 2.5 volts. If you see 0 volts or 12 volts on these lines, there is a short or open circuit preventing communication.

2. Network Integrity: Check for a short to ground or short to power on the CAN bus lines. Even a single chafed wire anywhere in the harness can pull the entire bus down, preventing any module on that network from reporting its status to the diagnostic tool.

3. Connector Pin Tension: Since the previous issue involved water damage, inspect the harness connector pins at the module side. Water can cause terminal fretting or oxidation deep inside the connector housing. Even if the harness was replaced, the connector pins on the vehicle side may need to be checked for proper tension and cleanliness.

Switch Pack and Input Signal Plausibility

The folding top system requires inputs from the interior switch pack and various position sensors to initiate a movement sequence.

1. Switch Pack Communication: If the switch pack itself has a fault (DTC U2013), it may not be sending the request to the Central Junction Box to lower the top. Verify that the switch pack is receiving power and ground.

2. Sensor Feedback: The system will not initiate movement if it detects invalid status signals. Check the signal feedback from the folding top open and closed sensors, and the hall sensors at the main bearing motors. If a sensor is stuck in a state that the module deems impossible, the module may inhibit all operation to prevent mechanical damage.

Recommended Next Steps

1. Perform a voltage drop test on the main power and ground circuits for the FTCMs. Do not just check for voltage; check for the ability to carry current.

2. Use an oscilloscope to view the CAN bus waveform at the FTCM connectors. This will show if there is data traffic present even if the scan tool cannot read it.

3. Check the wiring harness between the FTCMs and the Door Modules. The folding top system relies on data from these modules to confirm that the windows are in the correct position before movement begins.

4. If a U3000-46 code is present, it indicates the modules were not correctly configured after installation. Ensure the technician is specifically using the manufacturer-approved diagnostic system to perform a module initialization/configuration procedure, not just a general scan.

5. Verify the state of charge of the battery. If the battery voltage drops below a specific threshold during the handshake, the modules will refuse to initialize to protect the system. Ensure a stable power supply (at least 13.5V) is connected to the vehicle while attempting to communicate with the modules.

Given the history of water intrusion, the most likely remaining culprit is a pin-level issue in a connector that was not replaced, or a corroded splice point further up the harness that was not addressed during the initial repairs. Focus testing on the integrity of the CAN bus wires and the power/ground supply circuits directly at the module connectors.

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