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Home / DTC / U1204 — SAS message counter error

U1204 — SAS message counter error

Detailed page for trouble code U1204.

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Code

U1204

MITSUBISHI U — Network/User

SAS message counter error

Brand: MITSUBISHI
Type: U — Network/User
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Corrupted CAN frames or intermittent CAN bus communication
  • Faulty or intermittent Steering Angle Sensor (SAS) module
  • Damaged, corroded or loose wiring/connectors between SAS and CAN bus
  • Incorrect or mismatched software/calibration in SAS or receiving ECU
  • Loss of power or poor ground to the SAS module
  • Electromagnetic interference (EMI) or high impedance on CAN lines

Symptoms

  • SAS-related warning lamp(s) or stability control/ABS warning lights illuminated
  • Loss or degradation of electronic steering-angle-based functions (stability control, torque vectoring, lane assist)
  • Steering angle reading incorrect or unavailable in scan tool/live data
  • Intermittent or permanent fault codes related to CAN communications
  • Vehicle limp or reduced control system functionality in some cases

What to check

  • Use a capable scan tool to read U1204 plus any other stored network or SAS codes and view live steering angle and counter values
  • Inspect SAS connector and wiring for corrosion, bent pins, damage, or water ingress
  • Check vehicle battery state-of-charge and engine/vehicle grounds for corrosion or looseness
  • Scan the CAN bus: check for other U-codes, bus-off conditions, or frequent ECU resets
  • Measure CAN high/low idle voltages and termination (approx. 60 ohms across CAN_H/CAN_L) with multimeter/oscilloscope
  • Capture CAN waveform with oscilloscope to verify valid frames, timing and counter field behavior

Signal parameters

  • SAS CAN message contains a rolling counter/sequence field that should increment by 1 each message (wraps at defined maximum)
  • Typical message rate for SAS messages: typically tens of Hz (verify exact rate for vehicle model)
  • Expected CAN bus idle voltages: approximately 2.5 V common mode; differential swing on CAN_H/CAN_L during frames (use oscilloscope to confirm)
  • Expected termination: ~60 ohms between CAN_H and CAN_L (two 120Ω terminators in parallel)
  • Valid CAN frames include correct CRC/checksum and counter sequence — counter mismatch indicates frame integrity or module issue

Diagnostic algorithm

  1. Record freeze-frame and all stored DTCs. Note when fault occurs (ignition cycle, driving, steering).
  2. Check battery voltage and vehicle ground points; ensure stable power supply to SAS.
  3. Visually inspect SAS connector and wiring harness for damage, corrosion, pin fit, water ingress; repair as needed.
  4. Use a scanner to monitor live SAS data: steering angle value, message counter field, and message frequency while turning the wheel slowly; note whether counter increments normally.
  5. Check CAN bus health: use multimeter to verify termination resistance and idle voltages. If suspicious, use an oscilloscope to capture CAN frames and examine for corrupted frames, noise, missing counter increments or repeated frames.
  6. Swap or isolate segments if possible: disconnect other modules or harness branches to localize fault. Reconnect to see if error clears or changes.
  7. If wiring and bus are good, verify software/calibration and VIN-related programming for SAS and receiving ECUs; reflash or update per manufacturer bulletin if required.
  8. If fault persists and all communications/wiring are confirmed good, consider replacement of SAS module. After replacement or repair, clear codes and perform relearn/calibration procedure for SAS/steering angle if required.
  9. Road test and recheck live data to confirm counter increments normally and no recurrence of U1204.

Likely causes

  • Poor connector/corroded pins at SAS harness
  • Intermittent CAN low/high wiring short or open near SAS
  • SAS internal fault causing counter not to increment or to send bad values
  • Module programming/software mismatch after replacement or update
  • Weak battery/poor ground causing module resets and message counter mismatch

Fault status

⚠️ Status
SAS CAN message counter incorrect or not incrementing — integrity of steering angle messages on the network is compromised.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

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406

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