U1175

Code

Other U — Network/User

SCP (J1850) Invalid or Missing Data for Primary Id

Brand: Other

Type: U — Network/User

Views: UK: 23 EN: 51 RU: 29

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Page language: EN

One or more modules not present on scan tool or showing communication faults
Intermittent or permanent loss of related functions (e.g., body, instrument, HVAC)
Multiple U-codes or network errors recorded
MIL or warning lamps illuminated for affected systems
Unexpected behavior from modules that rely on the missing ID

Read all U-codes and module-specific codes; note which module reports the missing Primary ID
Verify scan tool can communicate on J1850/SCP and can display module IDs
Visually inspect connectors and wiring for the affected module and along the bus
Check module power and ground circuits for proper voltage and continuity
Measure bus idle voltage and listen for network activity with a scope or proper bus tester
Check termination resistor presence and resistance per vehicle specification

Protocol: J1850 (SCP family) — typical baud ~10.4 kbps (verify exact variant with manufacturer)
Expected Primary ID field present in module messages and within manufacturer-specified range
Bus signaling includes dominant/recessive states; abnormal idle voltage or stuck dominant may indicate fault
Message frequency: module should transmit ID info at intervals determined by manufacturer
Waveform should show clean packet structure; malformed frames indicate wiring/noise/software issues

Retrieve all stored and pending U-codes and note which module(s) reference the Primary ID issue.
Verify vehicle symptoms and try to reproduce while monitoring the network with a scan tool capable of showing J1850 traffic.
Inspect connectors, pins, and harness routing for the affected module. Repair any corrosion, bent pins, or damaged insulation.
Check and verify module supply and ground circuits. Repair any open or high-resistance connections.
Measure bus idle voltage and listen for activity. Use an oscilloscope or dedicated bus analyzer to capture message frames and confirm whether the Primary ID field is present and valid.
Verify termination resistor(s) and overall bus resistance; install or repair termination per manufacturer spec if incorrect.
Isolate the fault by disconnecting modules one at a time (where safe) to see if a specific module causes malformed messages.
If a single module fails to transmit a valid Primary ID, reprogram or replace the module after verifying correct part number and calibration. Reinstall any replaced modules per programming procedures.
After repairs, clear codes and perform a full functional test and road test to confirm the fault does not return.