U1004

Code

Other U — Network/User

SCP (J1850) Invalid or Missing Data for EEC Programming

Brand: Other

Type: U — Network/User

Views: UK: 30 EN: 90 RU: 40

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Interrupted programming session (battery disconnect, ignition off or tool disconnect)
Low or unstable battery voltage during programming
Corroded/damaged connectors or wiring on the SCP/J1850 network
Faulty or incompatible scan tool or programming files
Corrupted calibration file or incorrect software for the vehicle
Faulty EEC/ECM or other module on the SCP/J1850 network causing bus errors

Symptoms

Diagnostic trouble code U1004 stored during programming attempt
Programming or reflash operation fails or aborts
Multiple communication-related DTCs present on other modules
Vehicle may not accept new calibration or configuration changes
Possible intermittent communication errors on the SCP/J1850 bus

What to check

Verify battery state of charge and voltage (fully charged recommended)
Check for other U-codes or module communication faults with a capable scan tool
Inspect fuses and fusible links related to engine control and network power
Visually inspect wiring, connectors and grounds for the EEC/ECM and modules on the J1850/SCP bus
Confirm the scan tool and software version are compatible and authorized for this vehicle
Check TSBs and service information for known reflash requirements or special procedures

Signal parameters

SCP/J1850 bus idle voltage (nominal)
Message packet presence (frames/sec) on SCP/J1850 during programming
Message IDs and payload length for EEC programming packets
Checksum or CRC field value in programming packets
Timing between frames and response latency from EEC

Diagnostic algorithm

Record freeze frame and all active/confirmed communication codes. Check service info for U1004 guidance.
Ensure battery is fully charged (manufacturer recommended state) and maintain charger during diagnostics/reflash.
Verify scan tool identity, software and calibration file match vehicle VIN and part numbers; update tool if needed.
Clear the code and attempt to reproduce by performing the same programming operation; note exactly when the failure occurs.
Visually inspect and wiggle-test connectors, terminals and grounds at the ECM, instrument cluster and any intermediary nodes on the J1850/SCP bus.
Check fuses and power feeds to the ECM and bus; measure supply voltage and ground integrity at the ECM with ignition on and during a programming attempt.
Use an oscilloscope or lab scope capable of reading J1850/SCP signals to capture bus traffic during a programming attempt; confirm packets, timing, and checksum fields per OEM spec.
If an aftermarket module or previous repair is present on the bus, disconnect it and retry programming.
If bus wiring and communications are good but programming still fails, try loading a known-good calibration file or use a different OEM scan tool/host to rule out corrupt files or tool issues.
If diagnostics point to a defective ECM or persistent bus errors only when the ECM is connected, follow OEM procedures for ECM replacement and programming.
After repair or software update, perform a full system scan and confirm no residual communication codes remain and that the reflash completes successfully.