C0700 – Level Control Accessory Inflator Switch – Circuit High

By Reinier (Contact Me)
Last Updated 2023-10-02
Automobile Repair Shop Owner

Table of Contents

1. What Does Code C0700 Mean?
2. Where is the C0700 sensor located?
3. What are the common causes of code C0700?
4. What are the symptoms of code C0700?
5. Get Help with C0700

What Does Code C0700 Mean?

OBD II fault code C0700 is a generic trouble code that is defined as C0700 – “Level Control Accessory Inflator Switch – Circuit High” and is set when the PCM (Powertrain Control Module) or other control module detects an abnormally high current or voltage in the circuits that control/monitor the air suspension compressor and its associated switch gear.

NOTE: Even though trouble code C0700 is very common on many vehicles in the greater General Motors stable that are fitted with air suspensions, very few, if any trouble code databases and official GM sources list this code. Moreover, this code often appears on GM (and some other) vehicles that are not fitted with air suspensions. In these cases, code C0700 could appear as a pending code as a result of hardware/software incompatibilities or poor programming when the vehicle was built. In either case, the code can be safely ignored if the vehicle is not fitted with an air suspension system.

The practice of fitting air suspension systems to heavy full-sized SUVs and some trucks to improve the ride quality is a good one in theory, the execution of this practice often leaves much to be desired, and failures or malfunctions in the various components that make up an air suspension systems are extremely common, especially on some GMC and Cadillac models.

Nonetheless, in terms of operating principles, air suspension systems use pneumatic shock absorbers, as opposed to hydraulic shock absorbers, to absorb suspension movements. In practice, the pneumatic shock absorbers are filled with pressurized air from an onboard computer-controlled compressor that uses input data from ride height sensors on each wheel to calculate or change the vehicle’s ride height.

In addition, typical air suspension systems also incorporate sensors that measure changes in the vehicle’s ride height from side to side and from front to back when the vehicle negotiates corners or when the vehicle’s weight distribution changes. As a practical matter, the function of these sensors is to relay changes in the vehicle’s ride height at each wheel to a control module. This information allows one or more control modules to activate and control a complex system of valves, check valves and switches via intricate electrical circuits*, and interconnected pressure lines to increase or decrease the pressure in individual air shock absorbers to return the vehicle to an even keel.

* GMC Yukon DIN circuit diagram

Generally speaking, air suspension systems work well when the vehicle is new because many adjustments to the ride quality and ride height happen automatically to improve the vehicle’s stability at high speeds or when the vehicle traverses uneven road surfaces. For example, the PCM or other control module will automatically reduce a vehicle’s ride height at highway speeds to improve the vehicle’s stability and responses to steering and braking inputs. Similarly, the PCM or other control module will automatically increase the vehicle’s ride height on uneven unpaved roads to protect the vehicle’s underside.

However, long use, rough vehicle usage, or a lack of regular maintenance and servicing typically cause some components, such as wiring, pressure lines, switches, and pneumatic shock absorbers to deteriorate to the point where pressurized air begins to leak past seals and pressure fittings and joints. Once this process of deterioration starts, it can typically not be halted or reversed without replacing all leaking or suspect parts with new OEM or OEM-equivalent parts, but be aware that in many cases, the cost of restoring an air suspension system’s full functionality could run to several hundred dollars in parts alone.

Nonetheless, when the PCM or other control module detects an abnormal current or voltage in the circuits and switch gear that controls the onboard compressor, the implicated control module will recognize that it cannot control the vehicle’s air suspension system effectively. When this occurs, the implicated control module will set code C0700 and illuminate a warning light,

WARNING: This code should NOT be ignored if the vehicle is fitted with an air suspension system. Be aware that driving a vehicle with a defective air suspension system could have unpredictable consequences, including but not limited to losing control over the vehicle during braking or steering inputs, which could result in a potentially fatal crash.  

Where is the C0700 sensor located?

This image shows the principal components (rendered in green) of the air suspension system on a GM Suburban SUV. Note that the pneumatic shock absorbers are mounted in the same position as the hydraulic shock absorbers on a conventional suspension system.

We mentioned elsewhere that repairing an air suspension system could cost several hundred dollars in parts alone so in some cases, replacing an air suspension system with a conventional system could be more cost-effective than repairing an air suspension system.

What are the common causes of code C0700?

Some common causes of code C0700 could include one or more of the following-

• Damaged, burnt, shorted, disconnected, or corroded wiring and electrical connectors
• Defective or malfunctioning air compressor
• Defective or malfunctioning compressor switch gear
• One or more defective or malfunctioning ride height sensors
• Failed or failing PCM or other control module, but note that since this is a rare event, the fault must be sought elsewhere before any control module is replaced or reprogrammed

What are the symptoms of code C0700?

Common symptoms of code C0700 usually include one or more of the following-

• Stored trouble code and an illuminated warning light
• Depending on the vehicle and the nature of the problem, one or more additional suspension-related codes may be present along with C0700
• The air compressor may run continuously or not at all
• The air compressor may overheat
• The air compressor may emit mechanical grinding or rumbling noises when it runs
• The vehicle may “sag” on one or more corners
• It may be difficult to maintain directional control at some or all road speeds
• One or more tires may wear unevenly
• The vehicle may “nosedive” or sway dangerously during braking
• The suspension may “bottom out” on uneven road surfaces or when the vehicle is loaded
• The suspension settings may not work
• The air suspension may not be available

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