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P1645: Fuel Pump Resistor Switch Circuit Malfunction

OTHER MAZDA BUICK CADILLAC CHEVY GM GMC OLDSMOBILE
Severity
Medium
System
Manufacturer-Specific Powertrain
Last reviewed: Last updated:

Methodology: We combine code standards with complaint and reliability patterns, then review for clear, vehicle-first diagnosis steps.

Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

What Does P1645 Mean?

P1645 is a manufacturer-specific diagnostic trouble code: Fuel Pump Resistor Switch Circuit Malfunction. This code applies to OTHER, MAZDA, BUICK, CADILLAC, CHEVY vehicles. Unlike generic OBD-II codes, manufacturer-specific codes are defined by the vehicle maker and may only apply to certain makes and models.

Symptoms of P1645

Common Causes

Frequently Asked Questions

What does P1645 mean?
P1645 indicates: Fuel Pump Resistor Switch Circuit Malfunction. The vehicle's computer has detected that the Fuel Pump Resistor Switch is not operating within its expected parameters and stored this diagnostic trouble code.
Can I drive with code P1645?
You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P1645 for extended periods may cause additional problems.
How much does it cost to fix P1645?
Repair costs for P1645 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

  • 🔧 Inspect and repair Fuel Pump Resistor Switch wiring and connectors
  • 🔧 Replace faulty Fuel Pump Resistor Switch
  1. 1
    Find your vehicle above

    Click your make and model for real owner reports and common causes specific to your vehicle.

  2. 2
    Check for recalls

    Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.

  3. 3
    Get a professional diagnosis

    A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

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