Air Suspension Rear Circuit Fault
The C1726 code indicates that the air suspension control module (VSM or SCM) has detected a fault in the rear pneumatic circuit. This means the system cannot maintain or reach the target pressure in the rear air springs within the expected time, typically due to a significant leak or a stuck compressor vent solenoid.
1. Commonly Affected Makes
2. Most Common Causes
- Leaking rear air springs (air bags)
- Leaking air lines or fittings (hoses, connectors)
- Compressor vent/relief solenoid stuck open or leaking internally
- Worn air suspension compressor or faulty check valve
- Rear height sensor out of range or defective
- Faulty suspension control module (SCM/VSM)
3. Symptoms You Will Notice
- Vehicle sits low or uneven at the rear
- Air compressor runs continuously or cycles frequently
- Suspension warning light on the dashboard
- Rough ride or bottoming out over bumps
4. Step-by-Step Diagnosis
Check for diagnostic trouble codes (DTCs) and freeze frame data
Inspect rear air springs for cracks, leaks, or damage
Test air lines and fittings for leaks using soapy water or a smoke machine
Check compressor operation and vent solenoid function
Verify rear height sensor readings and adjustment
Test the suspension control module for proper output signals
5. Frequently Asked Questions
Is it safe to drive?▼
Driving with this code is not recommended as the vehicle may sag or handle poorly, increasing the risk of damage or loss of control. It is best to have it repaired promptly.
How much does it cost to fix?▼
Repair costs vary widely depending on the cause. A simple leak repair may cost $200-$500, while replacing a compressor or control module can range from $800 to $2,000 or more.