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MID 128 PID 45 FMI 4Severity: Warning

MID 128 PID 45 FMI 4: Preheater Relay - Voltage Below Normal (Volvo)

Quick Answer

Preheater Relay - Voltage Below Normal (Volvo)

Code
MID 128 PID 45 FMI 4
Severity
Warning
Applies to
Check OEM application
Can I drive?
Driving suitability is not established by this code alone.

Common Symptoms

  • Induction air is hot
  • Preheat relay impossible to turn off

Likely Causes

  • Short circuit to low source in measuring line
  • Faulty harness

Common Fixes

  • Check for shorts to ground in preheater circuit
  • Inspect relay for stuck-closed condition
  • Verify proper ground connections
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What does MID 128 PID 45 FMI 4 mean?

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Preheater Relay - Voltage Below Normal (Volvo)

Detailed guide for MID 128 PID 45 FMI 4

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MID 128 PID 45 FMI 4 - Preheater Relay

**Fault Type:** Voltage below normal or shorted to low source

Fault Condition

  • Short Circuit - (Measuring line)

Possible Symptoms

  • Induction air is hot
  • Preheat relay is impossible to turn off

Possible Causes

  • Faulty harness
  • Short circuit to ground

Diagnostic Tips

1. Check for shorts to ground in the preheater circuit

2. Inspect relay for stuck-closed condition

3. Verify proper ground connections at relay and ECU

4. Test relay operation with diagnostic tool

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