What Does C1790 Mean?
The left rear air spring or air shock solenoid output circuit has a general failure. This solenoid controls air flow into or out of the left rear air spring to maintain proper ride height. With this circuit failed, the left rear of the vehicle may sag, rise to full extension, or fail to level properly. The driver will typically see an air suspension warning message and may notice the vehicle sitting unevenly.
Common Causes
30%
Faulty left rear air spring solenoid valve (stuck, worn, or electrically failed)
25%
Wiring harness damage between suspension module and LR solenoid
20%
Corroded or water-damaged connector at the air spring solenoid
15%
Air suspension module output driver failure
10%
Damaged air spring assembly causing solenoid mechanical binding
Diagnostic Steps
1
Command the left rear solenoid on using the scan tool's bidirectional controls and listen for the solenoid click. Simultaneously monitor current draw — typical solenoid draws 0.5-1.5A when energized.
2
Disconnect the LR solenoid connector and measure coil resistance — typical spec is 3-10 ohms. Infinite resistance means an open coil; very low resistance suggests an internal short.
3
Check for voltage at the solenoid connector when commanding the solenoid on — should see battery voltage (11-14V) across the two pins. No voltage indicates a wiring or module output issue.
4
Inspect the wiring harness to the left rear air spring, particularly where it routes along the rear axle or suspension arm. Look for abrasion, cuts, and exposure to road debris and moisture.
5
Examine the connector at the solenoid for corrosion, pushed-back pins, or broken locking tab. Clean and apply dielectric grease, then retest.
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The left rear air spring or air shock solenoid output circuit has a general failure. This solenoid controls air flow into or out of the left rear air spring to maintain proper ride height. With this circuit failed, the left rear of the vehicle may sag, rise to full extension, or fail to level proper...
The most common cause of C1790 (Air Suspension LR Air Spring/Shock Solenoid Output Circuit Failure) is: Faulty left rear air spring solenoid valve (stuck, worn, or electrically failed)
Typical repair costs for C1790 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle may sit unevenly, affecting headlight aim, handling balance, and tire wear. Avoid highway driving if the vehicle is visibly sagging on one corner. At moderate speeds on surface streets, the vehicle is generally safe but ride quality and handling are compromised. Repair promptly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1790 to identify the root cause.
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Quick Info
Category
Chassis
System
Air Suspension System
Difficulty
Type
Manufacturer
Recommended Tools
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