How severe is fault code C1873?

Serious — Stop or limit driving

OBD Code C1873: Air Suspension RF Air Spring Solenoid Output Circuit Failure

Q: How do I fix OBD fault code C1873?

Inspect and reseat the solenoid electrical connector; clean corrosion from pins with contact cleaner.. Check the harness between ECU and RF solenoid for pinched, chafed, or melted insulation and repair with electrical tape or new wire.. Replace the solenoid if resistance testing shows 15 ohms and wiring is intact.

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What This Actually Means

In plain language — no jargon

The air suspension system's right-front solenoid valve isn't responding to electrical commands, like a light switch that won't turn the bulb on. The ECU can't control the air spring height on that corner because the solenoid circuit is broken or shorted.

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Symptoms You May Notice

3 known symptoms for this code

Right front corner sits lower than normal or won't adjust height

Suspension warning light illuminated on dashboard

Rough or uneven ride quality on right side

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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU sends a PWM control signal to the RF air spring solenoid and monitors the circuit for proper voltage and current draw. It detects opens, shorts, or excessive resistance in the solenoid coil wiring. If the measured circuit impedance falls outside normal range, a fault is logged.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Solenoid Coil Resistance	4-8 ohms	< 2 ohms (short) or > 15 ohms (open/high resistance)
Supply Voltage to Solenoid	11-14.5V when commanded	< 8V or 0V (open circuit)

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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Wiring harness connector at RF solenoid

Inspect and reseat the solenoid electrical connector; clean corrosion from pins with contact cleaner.

2

Solenoid wiring for damage

Check the harness between ECU and RF solenoid for pinched, chafed, or melted insulation and repair with electrical tape or new wire.

3

RF air suspension solenoid valve

Replace the solenoid if resistance testing shows < 2 ohms or > 15 ohms and wiring is intact.

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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code C1873 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.

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How to Clear Code C1873

What happens after you fix the fault

Once the fault is repaired, C1873 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When

Fault has been diagnosed and repaired
You want to confirm the repair worked
Code appeared after a sensor was cleaned

⚠️ Do Not Clear When

Preparing for an emissions/PUC test
Root cause is still undiagnosed
Check engine light is flashing

Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.