2017 Volvo S90 OBD2 Code B1918 Air Bag Memory Clear Circuit Open

B1918 code definition

The B1918 diagnostic trouble code is an indication that the air bag memory clear circuit is open and is faulty.

What the B1918 code means

The air bag system has its own module, separate from the powertrain control module (PCM). Trouble codes relating to the air bag system are stored in the air bag control module. Trouble codes are able to be cleared from the air bag control module with the proper scan tool after the stored code has been properly diagnosed and repaired. The air bag memory clear circuit is the component of the air bag system that makes this possible. Once a repair is completed, if the diagnostic trouble code related to that repair is unable to be cleared from the air bag control module, this indicates that there is a problem with the air bag memory clear circuit. The air bag control module will store the B1918 diagnostic trouble code and the air bag light will come on.

What causes the B1918 code?

• Blown air bag fuse
• Faulty instrument cluster
• Instrument cluster with damage, corrosion, or bent pins
• Air bag control module with damage, corrosion, or bent pins
• Wiring that is frayed, broken, shorted, or corroded
• Faulty air bag control module

What are the symptoms of the B1918 code?

• Air bag light stays on after clearing original diagnostic trouble code
• Air bag system may be disabled
• B1918 diagnostic trouble code stored in the air bag control module

How does a mechanic diagnose the B1918 code?

• Diagnostic trouble codes should be diagnosed in the order that they appear when scanned.
• Use an OBD-II scanner to collect all stored trouble codes as well as freeze frame data.
• Inspect the air bag fuse for failure. If the air bag fuse is blown out, replace the fuse and clear all stored trouble codes from the air bag control module.
• Complete a test drive to see if the B1918 diagnostic trouble code comes back.
• If the B1918 trouble code comes back, inspect wiring for frays, breaks, shorts, and corrosion. Repair and replace as necessary
• Inspect instrument cluster connectors for damage, corrosion, or bent pins. Repair or replace as necessary.
• Inspect air bag control module connectors for damage, corrosion, or bent pins. Repair or replace as necessary.
• Complete a test drive to see if the B1918 diagnostic trouble code comes back.
• If the B1918 trouble code comes back, inspect the instrument cluster for faults.
• Test the voltage signal and ground continuity of the instrument cluster wiring harness.
• If the voltage signal and ground continuity does not fall within the manufacturer's specifications, the instrument cluster wiring harness may need to be replaced.
• After replacing the instrument cluster wiring harness complete a test drive to see if the B1918 diagnostic trouble code comes back.
• If the B1918 trouble code comes back, test the instrument cluster to see if the voltage signal and ground continuity falls within the manufacturer's predetermined specifications.
• If the voltage signal and ground continuity does not fall within the manufacturer's specifications, the instrument cluster may need to be replaced
• After replacing the instrument cluster complete a test to see if the B1918 diagnostic trouble code comes back.
• If the B1918 trouble code comes back, the air bag module may need to be replaced.

Common mistakes when diagnosing the B1918 code

When diagnosing the B1918 trouble code, mistakes that are most commonly made by failing to inspect all of the related components. Make sure to inspect the instrument cluster, the wiring harness, and the fuses for the air bag system. It is important to ensure that there are no faults, damaged wiring, or blown fuses.

How serious is the B1918 code?

A diagnostic trouble code is normally considered serious when it causes driveability issues or a change in performance. Any problems with the air bag system are considered serious. In the event that the air bag system is completed disabled, the air bags will not deploy and this can be dangerous to the driver and passengers. It is important to have the B1918 diagnostic trouble code diagnosed and repaired immediately.

What repairs can fix the B1918 code?

• Replace blown air bag fuse
• Replace faulty instrument cluster
• Repair or replace instrument cluster wiring harness
• Repair or replace air bag control module wiring harness
• Repair or replace connectors that have damage, corrosion, or bent pins
• Repair or replace wiring that is frayed, broken, shorted, or corroded
• Replace air bag control module

Additional comments for consideration regarding the B1918 code

The air bag system should be disabled when repairs are being completed for the B1918 diagnostic trouble code. If the air bag system is not properly disabled, the air bags may deploy during the repair causing serious bodily injury.

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