Code
P0624
Generic
P — Powertrain
Fuel Cap Lamp Control Circuit
Views:
UK: 23
EN: 39
RU: 26
AI status
Completed
Completed
100%
Causes
- Open or short in lamp control wiring (power or ground)
- Faulty fuel-cap lamp or lamp socket
- Poor connector connection or corrosion
- Faulty body control module (BCM) / instrument cluster / PCM output
- Faulty fuel cap sensor or switch (if equipped)
- Aftermarket accessories or recent repairs that disturbed wiring
Symptoms
- Fuel cap / check fuel cap indicator lamp stays off or on incorrectly
- Malfunction Indicator Light (MIL) or dash warning related to fuel cap illumination
- Intermittent lamp operation (flickering)
- Stored P0624 DTC; possible related EVAP / fuel cap messages
What to check
- Read and record the exact DTC and freeze-frame data with a scan tool
- Visually inspect fuel cap, lamp, lamp socket, and nearby wiring for damage or corrosion
- Check fuses and relays supplying the lamp circuit
- Operate the lamp (turn ignition to ON) and observe behavior
- Wiggle wiring and connectors while observing lamp/scan tool for changes
- Check for related EVAP codes that could point to cap/sensor problems
Signal parameters
- Ignition ON: lamp supply voltage ≈ battery voltage (~12 V) when commanded ON
- Ignition OFF or command OFF: ~0 V or open circuit on supply/ground depending on design
- Expected lamp circuit continuity: low ohms (lamp filament present); open circuit indicates broken filament or open wiring
- Short to ground: near 0 Ω between supply and ground when lamp is ON (abnormal)
- Short to battery: continuity from lamp control output to battery positive with lamp OFF indicates short
Diagnostic algorithm
- Verify DTC P0624 with a scan tool; note freeze-frame and any related codes. Clear codes and see if P0624 returns.
- Inspect fuel cap and fuel-cap lamp assembly for visible damage, corrosion, or burned bulb/LED. Replace lamp or bulb if visibly failed.
- With ignition ON, measure voltage at the lamp connector: verify battery voltage when lamp should be ON and proper state when OFF. If no voltage, proceed to wiring checks.
- Inspect connectors and harness between lamp and BCM/cluster/PCM for corrosion, bent pins, or physical damage. Repair or replace as needed.
- Check fuse(s) and any inline resistors or modules in the circuit. Replace blown fuses and retest.
- Perform continuity test from module output to lamp connector (ignition OFF). Repair any opens or high-resistance sections. Check for short to ground or battery.
- Back-probe the module output while commanding lamp ON with a scan tool (if supported) to confirm module operation. If module does not drive but wiring is good, suspect BCM/cluster/PCM.
- After repairs, clear codes, verify lamp function, and perform a drive or ignition cycles to confirm DTC does not return.
- If wiring and lamp assembly are good but the module output is intermittent or incorrect, consider module replacement or professional reprogramming as final step.
Likely causes
- Damaged harness between BCM/ECM and fuel-cap lamp
- Corroded or loose connector at lamp or module
- Blown fuse supplying lamp circuit
- Lamp filament burned out or lamp assembly failure
- Grounding point loose or corroded
Fault status
Status
Controller detected fault in fuel cap lamp control circuit (open, short, or abnormal signal).
Repair difficulty: Medium
Diagnostic time: 0.8-2.5 hours
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