Code
P1245
MITSUBISHI
P — Powertrain
Engine ECU(RAM check)
Views:
UK: 17
EN: 24
RU: 20
AI status
Completed
Completed
100%
Causes
- Internal ECU RAM or processor fault
- Corrupted ECU software/firmware (failed update)
- Low or unstable battery/charging voltage during ECU power‑up
- Poor power/ground connections to the engine ECU
- Damaged/shorted wiring or connectors to the ECU
- Water intrusion/corrosion or physical damage to ECU
Symptoms
- Check Engine/MIL lamp illuminated
- Possible no-start or extended crank time
- Intermittent stalling or erratic engine behavior
- Loss of communication with ECU on diagnostic scanner (CAN/BUS errors)
- Stored related ECU diagnostic trouble codes and possibly immobilizer-related symptoms
What to check
- Read all stored and pending DTCs and freeze frame data with a capable scan tool
- Check for CAN/serial communication faults (no response from engine ECU)
- Verify battery resting voltage and cranking voltage (battery fully charged)
- Inspect ECU connectors and wiring for corrosion, bent pins, water ingress or damage
- Check main ECU power and ground circuits and fuses (measure for proper voltage at ECU harness)
- Review recent service history for ECU reflash, replacement or aftermarket electronics installation
Signal parameters
- Battery voltage (key ON): nominal 12.0–14.5 V
- Cranking voltage: should not drop below ~9.6 V under load
- ECU supply line (B+) at ECU connector: ~battery voltage with key ON
- Main ECU ground resistance to chassis: below 0.5 ohm preferred
- CAN bus idle differential voltage: ~2.5 V per line (check for activity when engine/ign is ON)
- ECU wake/ignition input voltage: matches key ON signal (near battery voltage)
Diagnostic algorithm
- Connect a scan tool; record all codes, freeze frame and communication status. Do not clear yet.
- Confirm code P1245 is current vs historic by attempting to recreate conditions and observing when code sets.
- Check battery state of charge and charging system; charge or replace battery if low and re-test.
- Visually inspect ECU and connector for corrosion, water damage, loose pins, or physical damage; repair wiring and connectors as needed.
- With ignition OFF, disconnect battery negative and check ECU connector pins for continuity to power/ground circuits per wiring diagram.
- With ignition ON, measure B+ and ground at the ECU connector and verify ignition feed and CAN lines have expected voltages/traffic.
- If wiring and supply are good, check for recent ECU reflashes or aftermarket modules; revert or reprogram per manufacturer guidance.
- Attempt to clear codes and perform key cycles; if P1245 returns immediately or ECU does not respond, suspect internal ECU fault.
- Before replacing ECU, consult manufacturer service literature for special reprogramming, immobilizer linking, and retrofit procedures; consider dealer-level reflash or replacement.
- If available, swap with a known-good/reprogrammed ECU only as a final verification step; ensure proper immobilizer and VIN programming after replacement.
Likely causes
- Faulty ECU internal RAM or processor (most likely)
- Low battery/poor charging during last ignition cycle
- Loose or corroded ECU power or ground connection
- Damaged ECU connector or wiring harness feeding ECU power/ignition
- Failed or incomplete ECU reflash or software corruption
Fault status
Status
Engine ECU RAM/self-check failed — internal memory or integrity error detected; ECU may be non‑responsive or operate erratically.
Repair difficulty: Hard
Diagnostic time: 2.0-4.0 hours
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