Code
P1451
FIAT
P — Powertrain
Intake air heater control fault
Views:
UK: 2
EN: 2
RU: 5
AI status
Completed
Completed
100%
Causes
- Open or short in intake air heater power or ground circuit
- Failed intake air heater element
- Blown fuse or faulty relay supplying the heater
- Corroded/damaged connector or wiring harness
- Faulty ECU driver output
- Water or contamination in heater assembly or connector
Symptoms
- Malfunction Indicator Lamp (MIL) / check engine light illuminated
- Hard or rough cold starting / poor cold driveability
- Longer warm-up time; possible increased white/black exhaust at cold start
- Reduced emissions performance during cold operation
- Possible stored freeze-frame data or repeated fault history
What to check
- Read freeze frame and pending/multiple occurrences with a scan tool
- Visual inspection of heater, connector, and wiring for damage or corrosion
- Check relevant fuses and relays for continuity and operation
- Backprobe connector and measure supply voltage and ground at rest and when commanded
- Measure resistance/continuity of the intake air heater element
- Use scan tool to command heater on/off and observe ECU output/status
Signal parameters
- Control command from ECU: on/off or PWM request (check with scan tool)
- Supply voltage at heater: ~battery voltage when commanded ON (may be switched via relay)
- Ground continuity: low resistance to chassis ground when commanded
- Heater element resistance: should show continuity (low ohms); open = failed element
- Current draw when commanded: measurable current consistent with heater resistance (no excessive draw or zero)
- ECU driver voltage/current: switching to ground or supplying voltage as per wiring diagram
Diagnostic algorithm
- Retrieve DTCs, freeze frame, and relevant live data with a scan tool. Record occurrences and conditions.
- Perform visual inspection: connectors, wiring harness, heater assembly for corrosion, damage, or loose pins.
- Check fuses and relays in the heater supply circuit. Replace any failed components.
- With ignition off, disconnect heater connector and measure element resistance to verify continuity. Replace if open or out of specification.
- Reconnect and backprobe connector. With ignition ON or engine as specified, command heater ON via scan tool; verify supply voltage at the power pin and switching at the control pin (ground or voltage switch) and measure current.
- If supply and ground are present but element does not draw current, suspect internal heater failure or poor connection. If element draws excessive current, check for short to ground or internal short and replace heater.
- If element and wiring check OK, test continuity between heater connector and ECU driver pin. If open or intermittent, repair wiring/connector.
- If wiring and heater are good but ECU output does not switch correctly, inspect ECU connectors and grounds; consider ECU driver fault and consult manufacturer guidance before ECU replacement.
- Repair/replace faulty wiring, connector, relay, fuse, or heater element as required. Clear codes and perform verification drive/cold-start cycles to confirm repair.
- If intermittent, perform wiggle tests and monitor live data while aging/temperature conditions replicate the fault.
Likely causes
- High-resistance or open heater element (internal failure)
- Broken wire or pinched harness between heater and ECU
- Blown fuse or sticking/failing relay feeding the heater
- Corroded or loose connector at the heater or ECU
- ECU control transistor or driver fault
- Short to battery or ground causing incorrect current draw
Fault status
Status
Intake air heater control circuit fault detected — check heater element, fuses/relay, wiring and ECU control.
Repair difficulty: Medium
Diagnostic time: 1.0 - 3.0 hours
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