What Does B1998 Mean?
This code indicates the Airbag Control Module (ACM) has detected an open circuit in the passenger side-mounted (torso/thorax) airbag deployment circuit. An open circuit means there is a break in electrical continuity between the ACM and the side airbag inflator, preventing proper deployment signal transmission. This safety system fault disables the passenger side airbag and typically illuminates the airbag warning light on the instrument cluster.
Safety Warning
The vehicle is technically drivable but the passenger side airbag will NOT deploy in a collision, creating serious injury risk for passengers. This repair should be completed immediately before allowing passengers in the vehicle, as federal safety regulations require functional airbag systems.
Common Causes
45%
Damaged or disconnected wiring harness under passenger seat due to seat movement, corrosion, or physical damage
30%
Faulty passenger side airbag module with internal open circuit or corroded connection terminals
15%
Loose or corroded connector at airbag module or under-seat connection point
10%
Failed Airbag Control Module unable to properly monitor circuit resistance
Diagnostic Steps
1
Step 1: Disconnect vehicle battery and wait 10 minutes for airbag system capacitor discharge. Visually inspect passenger seat base and wiring harness for obvious damage, chafing, pinched wires, or disconnected connectors
2
Step 2: Using a digital multimeter set to ohms, measure resistance across the side airbag inflator connector terminals (disconnected from harness). Typical resistance should be 2-3 ohms; infinite resistance confirms internal airbag failure
3
Step 3: If airbag resistance is normal, inspect and measure continuity through the entire harness from airbag connector to ACM connector. Check for open circuits, damaged insulation, and corroded terminal pins at all connection points
4
Step 4: Test ACM connector pin circuits for proper voltage supply (typically 12V ignition-on) and ground integrity using wiring diagrams specific to vehicle make/model
5
Step 5: If all wiring and connections test normal, suspect failed ACM. Reconnect battery, clear codes, and perform system retest. If code returns immediately without physical fault, replace ACM
6
Step 6: After repairs, perform airbag system self-test using scan tool to verify proper circuit operation and confirm airbag warning light extinguishes
Estimated Repair Cost
$150 - $1,200
Parts + labor, varies by vehicle and location
This code indicates the Airbag Control Module (ACM) has detected an open circuit in the passenger side-mounted (torso/thorax) airbag deployment circuit. An open circuit means there is a break in electrical continuity between the ACM and the side airbag inflator, preventing proper deployment signal t...
The most common cause of B1998 (Passenger Sid, Side mount Airbag Circuit Open) is: Damaged or disconnected wiring harness under passenger seat due to seat movement, corrosion, or physical damage
Typical repair costs for B1998 range from $150 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The vehicle is technically drivable but the passenger side airbag will NOT deploy in a collision, creating serious injury risk for passengers. This repair should be completed immediately before allowing passengers in the vehicle, as federal safety regulations require functional airbag systems.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to B1998 to identify the root cause.
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Quick Info
Category
Body
System
Supplemental Restraint System (SRS/Airbag)
Difficulty
Type
Manufacturer
Recommended Tools
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