What Does C1931 Mean?
The air suspension module has detected a short-to-battery condition in the front compressor relay circuit. A voltage source is feeding the relay control wire, which may cause the relay to be energized continuously, running the compressor non-stop. This can damage the compressor motor from overheating and overpressurize the air suspension system.
Common Causes
40%
Chafed relay control wire contacting a 12V power feed in the fuse box or harness
25%
Relay contacts welded closed from excessive current draw, keeping the compressor circuit energized
25%
Contaminated relay socket bridging control to power terminals
10%
Module internal short on the relay driver output
Diagnostic Steps
1
Step 1: Remove the relay and check if the compressor stops. If it does, the relay contacts are welded — replace the relay.
2
Step 2: With relay removed, check for voltage on the control terminal at the socket. Voltage present with module not commanding indicates a wiring short.
3
Step 3: Measure resistance from the control wire to B+ to locate the short source.
4
Step 4: Inspect the fuse box and harness for chafed wiring or crossed terminals.
5
Step 5: Replace the relay and monitor compressor cycle times. It should run briefly and shut off when target pressure is reached.
Estimated Repair Cost
$20 - $350
Parts + labor, varies by vehicle and location
The air suspension module has detected a short-to-battery condition in the front compressor relay circuit. A voltage source is feeding the relay control wire, which may cause the relay to be energized continuously, running the compressor non-stop. This can damage the compressor motor from overheatin...
The most common cause of C1931 (Air Suspension Front Compressor Relay Circuit Short To Battery) is: Chafed relay control wire contacting a 12V power feed in the fuse box or harness
Typical repair costs for C1931 range from $20 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A continuously running compressor can overheat and fail catastrophically. Overpressurization of air springs can cause them to burst. If the compressor runs non-stop, disconnect the relay until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to C1931 to identify the root cause.
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Quick Info
Category
Chassis
System
Air Suspension System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
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