What Does C1791 Mean?
The left rear air spring solenoid output circuit is open, meaning there is a break in the electrical path between the air suspension module and the solenoid valve. The module cannot energize the solenoid to add or release air from the left rear air spring. The vehicle may sag on the left rear corner and display an air suspension warning.
Common Causes
30%
Broken or disconnected wiring in the solenoid control circuit
30%
Open coil in the left rear air spring solenoid (burned out)
20%
Disconnected or damaged connector at the solenoid
15%
Corrosion causing high resistance open in connector pins
5%
Air suspension module connector issue or open driver circuit
Diagnostic Steps
1
Disconnect the left rear solenoid connector and measure coil resistance — should be 3-10 ohms. If OL (infinite), the solenoid coil is open and the solenoid must be replaced.
2
If the solenoid coil tests good, measure continuity of each wire from the solenoid connector back to the air suspension module connector — should be less than 2 ohms on each wire.
3
Inspect both connectors (at solenoid and at module) for pushed-back terminals, broken wires at crimp points, and corrosion that could cause an intermittent open.
4
Wiggle-test the harness while monitoring the solenoid circuit resistance to identify intermittent opens caused by broken wire strands inside intact insulation.
5
If all wiring tests good, command the solenoid on via the scan tool and check for voltage output at the module connector — absent voltage confirms a module output driver failure.
Estimated Repair Cost
$100 - $700
Parts + labor, varies by vehicle and location
The left rear air spring solenoid output circuit is open, meaning there is a break in the electrical path between the air suspension module and the solenoid valve. The module cannot energize the solenoid to add or release air from the left rear air spring. The vehicle may sag on the left rear corner...
The most common cause of C1791 (Air Suspension LR Air Spring/Shock Solenoid Output Circuit Open) is: Broken or disconnected wiring in the solenoid control circuit
Typical repair costs for C1791 range from $100 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The left rear corner cannot be leveled. If the vehicle is visibly sagging, headlight aim will be high on the opposite side, potentially blinding oncoming traffic at night. Handling and braking balance are affected. Drive at reduced speeds and have the repair completed soon.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1791 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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