Code
C1950
ALFA ROMEO
C — Chassis
Stack overflow/underflow
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UK: 4
EN: 6
RU: 4
AI status
Completed
Completed
100%
Causes
- ECU software bug or corrupted firmware/calibration
- Interrupted flash/programming or failed software update
- Low or unstable supply voltage (brownouts) or voltage spikes
- Poor or intermittent ground or battery connections
- Electrical overstress or ESD damage to the ECU
- Memory hardware fault inside the ECU
Symptoms
- MIL/airbag/ABS/ESP (depending on module) may be illuminated or the module may set internal error flags
- Intermittent loss of communication with the affected module (CAN U0100-style symptoms)
- Module reboots, freezes, or intermittent functionality
- Related system goes into limp mode or behaves erratically
- Stored history of multiple resets, watchdog events or software exception counters
What to check
- Read all stored and pending DTCs and freeze-frame data from the affected module and any linked modules
- Check module event logs, exception counters, watchdog reset counts and uptime if available
- Inspect battery condition, terminal connections and main ground straps; measure resting and cranking voltage
- Visually inspect ECU connector, pins and housing for corrosion, water ingress or damage
- Scan the vehicle CAN/LIN bus for communication errors (error counters, bus load, fault frames)
- Check for recent software updates, recalls or technical service bulletins (TSBs) for the module
Signal parameters
- Module watchdog reset count
- Module uptime since last power-on
- RAM/stack/heap error counters (if available in logs)
- Battery voltage (rest and cranking) and transient voltage spikes
- CAN/LIN error counters and bus voltage levels
- Number of ignition cycles since last update or failure
Diagnostic algorithm
- Retrieve complete vehicle DTC history and freeze frame for the module and related modules (store externally).
- Verify battery state of charge and condition; clean and tighten battery terminals and main grounds. Recheck after restoration.
- Inspect ECU connectors, pins and wiring for corrosion, damage or water ingress; repair as needed.
- Check CAN/LIN bus health with a scope or advanced scan tool; clear bus errors and repeat test to see if event reoccurs.
- Clear codes and attempt to reproduce fault under conditions found in freeze frame (note reproducibility).
- If not readily reproducible, perform an ECU power-supply stress test (monitor voltage during ignition/accessory events) to identify brownouts or spikes.
- Confirm software/firmware/calibration ID against manufacturer database; if older or flagged, perform official reflash/update using OEM tool. Do not use generic reflashing tools unless approved.
- After reflashing, monitor for recurrence. If errors persist and wiring/power/ground and bus are good, suspect internal ECU hardware failure.
- Consult manufacturer technical support for known software defects and provide logs; follow OEM procedures which may include module replacement or board-level repair.
- If replacement is required, ensure correct software and coding is applied and re-run tests to confirm resolution.
Likely causes
- Recent ECU update or reflash that failed or is incompatible
- Weak battery or poor battery terminal/ground connection causing resets
- Water ingress, corrosion or physical damage to ECU connectors or board
- Aged ECU with failing memory components
- Transient high-voltage event on the vehicle electrical system
Fault status
Status
ECU detected stack overflow/underflow (software stack pointer out-of-range). Module may have reset or lost communication; investigate software integrity, power/ground and bus conditions.
Repair difficulty: Hard
Diagnostic time: 1.5-4.0 hours
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