OBD-II Diagnostic Trouble Code
C1155 — Air Bag Crash Sensor
C1155 is listed as an air bag crash sensor fault, but this code number is manufacturer specific and on some platforms is used for a different chassis input such as a wheel speed sensor. In the air bag sense, the restraint module saw an open, short or invalid signal from a crash sensor. Confirm the definition for the exact truck.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Air Bag Crash Sensor
Code
C1155
Category
Chassis
Subsystem
Safety
Truck-relevant
Yes
What this means for truckers
C1155 (Air Bag Crash Sensor) — crash sensor fault. Safety-critical.
Before you replace parts — try this first
C1155 on the Safety system is most often crash sensor wiring or connector damage — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Air bag lamp on and air bags may not deploy. Otherwise the truck drives normally.
Common causes
- CommonCrash sensor wiring or connector damage ($80–$300)
- OccasionalFailed crash sensor ($150–$500)
- OccasionalSensor or mounting damaged in a collision ($150–$600)
- RareRestraint module fault ($400–$1200)
How to fix
Confirm the code definition
When to use: First step
Inspect sensor wiring, connectors and mounting
When to use: Corrosion, collision or body damage
Replace the crash sensor
When to use: Sensor fails test
Replace the restraint module
When to use: Wiring and sensor are good
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
Frequently Asked Questions
Can I drive with code C1155?
Drive with caution. C1155 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix C1155 on a commercial truck?
Total repair cost ranges $80–$1200 depending on the root cause. The cheapest fix is usually the first one listed below — Crash sensor wiring or connector damage — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will C1155 fail a DOT inspection?
C1155 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between C1155 and related codes?
C1155 is closely related to: C1100 (ABS - Internal Solenoid Coil Failure), C1102 (ABS Indicator Lamp Always On), C1145 (Air Bag Diagnostic Module). These codes share the same subsystem (safety) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only C1155 is set without the companions, the issue is more isolated.
How do I prevent C1155 from coming back after a repair?
For C1155 (Air Bag Crash Sensor), prevention centers on the safety system. Don't disconnect the battery without the key off and a 5-minute wait — capacitors can hold airbag-deployment charge. Don't jumper or test airbag circuits with a multimeter (use OEM scan tool). Replace seat belts and connectors that have been involved in a deployment.