Code
U1716
FIAT
U — Network/User
CAN bus communication between engine control module and cruise control adaptation
AI status
Completed
Completed
100%
Causes
- Open, short or intermittent wiring on the CAN high/low pair between ECM and cruise control module/adaptation harness
- Poor or corroded connector pins or poor ground
- Missing or incorrect CAN termination (open/shorted 120 Ω resistors)
- Faulty ECM or cruise control adaptation module (internal failure)
- Software/calibration mismatch or corrupted module programming
- Electrical interference or low battery/unstable supply voltage
Symptoms
- Cruise control will not engage or cannot be set
- Cruise control adaptation/calibration function unavailable or fails
- ECM or cruise control related warning lamps or messages
- Multiple communication-related DTCs stored on scan tool
- Intermittent or permanent loss of cruise-related functions
- Vehicle may enter limited functionality (reduced features) if controllers lose coordination
What to check
- Read all DTCs and freeze frame data from ECM and other modules on same CAN bus
- Check battery and charging system voltage and grounds for stability
- Visual inspection of CAN wiring harness and connectors for damage, corrosion, or loose pins
- Verify CAN bus termination resistance (approx. 60 Ω across CAN_H to CAN_L) with ignition off
- Measure idle CAN voltages and waveform with a scope (compare to expected levels)
- Scan for other modules reporting bus errors or bus-off status
Signal parameters
- Idle (recessive) voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (both near mid-rail)
- Dominant state: CAN_H ≈ 3.5 V, CAN_L ≈ 1.5 V (differential ≈ 2.0 V)
- Bus differential (dominant - recessive) typical ≈ 2.0 V
- Termination resistance: about 60 Ω measured across CAN_H and CAN_L (two 120 Ω in parallel)
- Typical bus speeds used on vehicles: 250 kb/s or 500 kb/s (confirm manufacturer specification)
- Watch for missing or repeated messages from cruise adaptation within expected message interval (use OEM datalogger)
Diagnostic algorithm
- Retrieve and record all stored and pending DTCs from ECM and other modules. Note freeze-frame data and history.
- Clear codes, perform key cycles, and see if U1716 returns immediately or only under certain conditions (intermittent vs permanent).
- Visually inspect CAN connectors and harness for damage, corrosion, water ingress, or pin push-out at ECM and cruise control module.
- Check vehicle battery voltage and engine ground connections; low or unstable supply can cause communication faults.
- With ignition off, measure resistance between CAN_H and CAN_L at a convenient junction; expect ~60 Ω. If open or far from 60 Ω, trace for missing termination or open circuit.
- Power vehicle, measure CAN_H and CAN_L DC voltages (recessive) at relevant connectors; compare to expected ~2.5 V. If abnormal, isolate section of bus by disconnecting branches one at a time and re-measuring.
- Use an oscilloscope or CAN bus analyzer to view waveforms and message traffic. Look for excessive noise, missing frames, or a module stuck in bus-off state.
- Perform a wiggle test on harness while monitoring live CAN traffic to find intermittent connector/wire faults.
- If a module is not responding, swap with known-good unit (if available and appropriate) or attempt reflashing/updating calibration per OEM service instructions.
- After repairs, clear codes and verify normal operation and that U1716 does not return during road test and diagnostic checks.
Likely causes
- Loose/corroded connector at ECM or cruise control adaptation connector
- Damaged wiring harness or chafed wires on CAN-H/CAN-L pair
- Failed termination resistor(s) or wrong bus topology after repairs
- Faulty cruise control adaptation module software or module hardware
- Intermittent battery/charging system voltage causing bus errors
Fault status
Status
CAN communication fault between ECM and cruise control adaptation — messages missing or invalid. Check CAN wiring, termination, module connections and software.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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