Code
P1620
FIAT
P — Powertrain
Gas ECU fault
Views:
UK: 5
EN: 7
RU: 11
AI status
Completed
Completed
100%
Causes
- Loss of power or ground to the gas ECU (blown fuse, faulty relay, damaged ignition feed)
- Damaged or corroded connectors or wiring to the gas ECU
- Faulty or intermittent CAN/LIN serial communication between gas ECU and main ECU(s)
- Internal gas ECU hardware fault or failed processor/board
- Corrosion or water ingress in the gas ECU or connectors
- Software/firmware mismatch or corrupted calibration
Symptoms
- Check Engine/MIL lamp illuminated
- Vehicle fails to switch to gas or reverts to petrol-only operation
- Rough idle, hesitation or stalling when attempting to run on gas
- Loss of gas-related functions on instrument cluster or dash messages
- Intermittent or permanent limp-home behaviour related to fuel system
What to check
- Read freeze-frame data and live data with a capable scan tool; note any related communication errors
- Confirm code is current vs historic; attempt to clear and see if it returns
- Visually inspect gas ECU connectors for corrosion, water, bent pins or damage
- Check fuses and relays that feed the gas ECU and replace if faulty
- Verify battery and ignition-switched supply voltages at the gas ECU
- Check ground continuity from gas ECU to chassis/engine ground
Signal parameters
- Battery/supply voltage at gas ECU (key ON/run): ~11–14.5 V expected
- Ignition-switched feed present when key ON
- Ground resistance: low (typically
- CAN bus idle voltage: approx. 2.5 V on each CAN line (expect differential signalling); dominant state expected when active
- No short to battery or ground on communication lines; no high-resistance connection on supply/ground
Diagnostic algorithm
- Connect a full-featured scan tool. Record DTCs, freeze frame and live data. Note related module errors.
- Attempt to communicate with the gas ECU via the scanner. If there is no response, suspect power/ground or communication fault.
- Inspect the gas ECU connector and harness for corrosion, damage, water ingress or rodent chew. Repair as required.
- Verify fuses/relays feeding the gas ECU. Replace any faulty items and retest communication.
- Measure supply voltage at the ECU with key ON and engine running. Verify proper grounding continuity to chassis/engine.
- Check CAN/LIN bus continuity and resistance; look for shorts to battery/ground and correct termination. Use an oscilloscope to inspect signal integrity if available.
- If wiring, power and communication are confirmed good and fault persists, consider ECU software update or reflashing per manufacturer procedure.
- If all tests indicate internal ECU failure, replace the gas ECU and follow any manufacturer programming/initialisation procedures. Re-scan and road-test to confirm repair.
- If fault is intermittent, perform wiggle testing of harnesses and re-check after vehicle cycles and exposure to moisture/temperature changes.
Likely causes
- Poor electrical connection at the gas ECU (pin corrosion, loose connector)
- Blown fuse or faulty relay supplying gas ECU
- CAN bus wiring short/open or missing termination resistor
- Failed gas ECU (most likely if power/can are correct and wiring checks good)
Fault status
Status
Gas ECU fault — communication, power/ground or internal failure detected in the LPG/CNG gas control ECU (manufacturer-specific code).
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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