How do I fix OBD fault code C1790?

Inspect connector pins for corrosion, bent terminals, or loose connections at the LR air spring solenoid and clean or reseat as needed.. Replace the faulty solenoid valve if connector and wiring are confirmed good.. Test and replace the air suspension relay if solenoid replacement doesn't resolve the fault.

How severe is fault code C1790?

Serious — Stop or limit driving

OBD Code C1790: Air Suspension LR Air Spring/Shock Solenoid Output Circuit Failure

💬

What This Actually Means

In plain language — no jargon

The air suspension control module can't properly activate the solenoid valve that controls air pressure to your left-rear air spring, similar to a valve getting stuck and unable to open or close. This prevents the suspension from adjusting height or stiffness correctly.

⚡

Symptoms You May Notice

3 known symptoms for this code

Left rear corner sits lower than normal or won't adjust height

Harsh or bouncy ride quality at rear left

Air suspension warning light on dashboard

🔬

How Your ECU Detects This

Technical sensor logic and voltage thresholds

The air suspension module monitors the solenoid coil resistance and electrical current flow when commanding the LR air spring solenoid. It detects open circuits, shorts, or excessive resistance that prevent proper valve activation. The module compares actual solenoid response against expected voltage and current patterns.

Voltage & Parameter Thresholds

Parameter	Normal Range	Fault Condition
Solenoid Coil Resistance	4-8 ohms	Open circuit (>15 ohms) or short (<2 ohms)
Solenoid Activation Current	0.5-2.0 amps during command	Zero current or excessive current draw

🔧

Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex

1

Solenoid connector and wiring harness

Inspect connector pins for corrosion, bent terminals, or loose connections at the LR air spring solenoid and clean or reseat as needed.

2

Air suspension solenoid valve (LR)

Replace the faulty solenoid valve if connector and wiring are confirmed good.

3

Air suspension control module relay

Test and replace the air suspension relay if solenoid replacement doesn't resolve the fault.

⚠️

When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code C1790 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.

🔄

How to Clear Code C1790

What happens after you fix the fault

Once the fault is repaired, C1790 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.