U 1900 on 2007 Ford 6.0L Diesel 350 Super Duty

Hi. I had a truck come in recently with this code and symptoms. I looked inside the power distribution box and found 1 blown fuse (for the ECM) and under the driver's side dash I found 3 blown fuses (power outlet, trailer brakes and gauge cluster). After replacing the fuses I turned the ignition switch to the run position, no fuses blew. I hooked up my scan tool and ran a KOEO test. The test ran and showed a open/short to the engine fan clutch. Further diagnostics revealed that the fan blade cut the electrical control cable to the fan and the harness lock on the inner fan shroud was missing. The cause of the missing lock could of been human error or age and heat. The lock is plastic so I tend to think it was age and heat. A new fan is over $600. so I tried repairing the harness and succeeded (Not Easy). Put everything back together, repaired the lock on the inner shroud (VERY IMPORTANT THAT THE LOCK HOLDS THE FAN HARNESS!!!) or the fan will cut the harness again. Started the truck, warmed it up and ran the KOER test. The systems passed, cleared the codes, road test and shipped it. I don't know if this will help but it is worth a try. The First answer from Jeff Armer is excellent. I respect and admire details. Please write back if there is anything else. Good Luck.

U1900 CAN Communication Bus Fault - Receive Error ABS Module REFER to Section 418-00 . U1900 CAN Communication Bus Fault - Receive Error Instrument Cluster REFER to Section 418-00 . U1900 CAN Communication Bus Fault - Receive Error TBC Module REFER to Section 418-00 .


Your best bet , have a qualified technician diagnose it .

Communications Network Vehicle communication utilizes a high speed controller area network (HS-CAN), International Standards Organization (ISO) 9141 network and universal asynchronous receiver-transmitter (UART)-based protocol (UBP) network. Information is sent to and from individual control modules that each control specific functions. All 3 networks are connected to the data link connector (DLC). The DLC can be found under the instrument panel between the steering column and the audio unit.
The 3 module communication networks are:

• High speed (HS) CAN
• ISO 9141
• UBP

ISO 9141 is for diagnostic use only while UBP and CAN allow multiple modules to communicate, or transfer data, with each other on a common network.



Module Name Network Type Termination Module Anti-lock brake system (ABS) module HS-CAN No Electronic automatic temperature control (EATC) module (if equipped) UBP N/A Instrument cluster (gateway module) HS-CAN and UBP Yes Parking aid module (PAM) (if equipped) ISO 9141 N/A Powertrain control module (PCM) HS-CAN Yes Restraints control module (RCM) ISO 9141 N/A Trailer brake control (TBC) module (if equipped) HS-CAN No Vehicle security module (VSM) (if equipped) UBP N/A Four wheel drive (4WD) control module (if equipped) ISO 9141 N/A
ISO 9141 Network Operation
The ISO 9141 communication network is a single wire network, used for diagnostic purposes only.
The ISO 9141 communication network is used for the following modules:

• Parking aid module
• RCM
• 4WD control module

UART-Based Protocol (UBP) Communication Network
The UBP communication network is a single wire network. In addition to scan tool communication, this network allows sharing of information between all modules on the network.
The UBP communication network is used for the following modules:

• EATC
• Instrument cluster
• Vehicle security module

HS-CAN Network Operation
The HS-CAN network uses an unshielded twisted pair cable, data bus (+) and data bus (-) circuits. In addition to scan tool communication, this network allows sharing of information between all modules on the network.
The HS-CAN is a high speed communication network used for the following modules:

• ABS module
• Instrument cluster
• PCM
• Trailer brake control module

Network Termination
The CAN network uses a network termination circuit to improve communication reliability. The network termination of the CAN bus takes place inside the termination modules by termination resistors. Termination modules are located at either end of the bus network. As network messages are broadcast, in the form of voltage signals, the network voltage signals are stabilized by the termination resistors. Each termination module has a 120 ohm resistor across the positive and negative bus connection in the termination module. With two termination modules on each network, and the 120 ohm resistors located in a parallel circuit configuration, the total network impedance, or total resistance is 60 ohms.
Network termination improves bus message reliability by:

• stabilizing bus voltage.
• eliminating electrical interference.

Gateway Module
The instrument cluster is the gateway module, translating HS-CAN to MS-CAN and vice versa. This information allows a message to be distributed throughout both networks. The instrument cluster is the only module on this vehicle that has this ability.



All you need to do is find out which module isn't communicating

Communication Network Diagnostic Trouble Codes (DTC) Index NOTE: DTC U1900 will set in a module that is reporting a communication fault from another module on the data bus. The module that reports the fault is not the problem module. DTC Description Source Action U0073 Control Module Communication Buss Off ABS module DTC U0073 indicates the module could not communicate on the network at a point in time. The fault is not currently present. CLEAR the DTC. REPEAT the network test with scan tool. U0073 Control Module Communication Buss Off Instrument cluster DTC U0073 indicates the module could not communicate on the network at a point in time. The fault is not currently present. CLEAR the DTC. REPEAT the network test with can tool. U1900 CAN Communication Bus Fault-Recieve Error ABS module For module that failed network test, GO to Symptom Chart . U1900 CAN Communication Bus Fault-Recieve Error Instrument cluster For module that failed network test, GO to Symptom Chart . U1900 CAN Communication Bus Fault-Receive Error TBC module For module that failed network test, GO to Symptom Chart . U1950 UBP Communication Bus Fault Vehicle security module For module that failed network test, GO to Symptom Chart . U2023 Fault Received From External Node Instrument cluster RETRIEVE and FOLLOW non-network DTCs from other modules. REFER to Section 419-10 . U2226 UBP Invalid Data From Node ID $10 (PCM) Vehicle security module RETRIEVE and FOLLOW non-network DTCs from the PCM. REFER to Powertrain Control/Emissions Diagnosis (PC/ED) manual. All other DTCs - - REFER to Section 419-10 .