P0624
Fuel Cap Lamp Control Circuit
Powertrain Emission Controls Fuel Cap Warning System 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The ECU can't control the fuel cap warning lamp circuit properly, like a dashboard light that won't turn on or off when it should. This usually means there's a wiring or module problem preventing the warning system from functioning.

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Symptoms You May Notice
3 known symptoms for this code
Fuel cap warning lamp stays on continuously
Fuel cap warning lamp won't illuminate when cap is loose
Check Engine light illuminates along with fuel cap warning
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the fuel cap lamp control circuit for proper voltage and continuity when signaling the instrument cluster. It detects open circuits, shorts to ground, or shorts to voltage that prevent the lamp driver from functioning correctly.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Lamp Control Circuit Voltage 0V (off) or 12V (on) with proper switching Stuck voltage, no voltage response, or short circuit detected
Circuit Continuity/Resistance Less than 5 ohms when activated Open circuit (infinite resistance) or shorted condition
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Fuel cap
Inspect and reseat the fuel cap firmly, then clear the code to see if the circuit resets.
2
Wiring harness and connectors
Check for corroded, loose, or damaged connections on the fuel cap lamp circuit and clean or tighten as needed.
3
Instrument cluster bulb or LED
Test and replace the fuel cap warning lamp if it's burned out or malfunctioning.