What Does the Engine Code B0090 Mean?

Engine code B0090 is an indicator of an unusual connection or configuration between the front left restraint sensor and the restraints control module.
Written by Holden Easterbrook
Reviewed by Melanie Reiff
A B0090 engine code means that your front left restraint sensor is suffering from a poor connection or unusual configuration with the restraints control module (RCM). For your safety, have your front left seatbelt inspected by a professional mechanic right away.
Diagnostic trouble codes (DTCs) are how your car notifies you and your mechanic about problems within one of its systems. To read engine codes, you need an
OBD-II code reader
, but you can count on your mechanic already having one handy.
To properly locate and fix the problems plaguing your car, you’ll need to know the meaning behind the engine code being displayed. That’s why
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What does the engine code B0090 mean?

Definition: Left Frontal Restraints Sensor 1
The engine code B0090 indicates a problem with the restraint sensor that monitors the driver’s seatbelt. These sensors aren’t just important for reminding you to wear your seatbelt—without them, there’s no way to tell that a seatbelt is in working order and able to protect you in the event of an accident.

How much will it cost to fix?

Diagnosing the cause of a B0090 engine code should take a skilled mechanic no more than an hour. Because the cost of labor varies depending on the location, expect to pay between $75 and $150.
It’s difficult to predict the cost of any replacement parts or required installation time since it is so dependent on the make and model of your vehicle. However, you can anticipate a total
car repair
bill of at least $100 or more.

What can cause the B0090 engine code?

B0090 engine codes are caused by the restraints control module (RCM) receiving signals from an improperly configured or faulty left frontal restraints sensor. This DTC is often flagged due to a worn or damaged sensor.
The frontal left restraint sensor monitors the driver’s seatbelt. Along with reminding you to use your seatbelt when operating your vehicle, the sensor also ensures that the seatbelt is configured and functioning within factory standards. Combined with the primary airbag and curtain airbags, this portion of the supplemental restraint system ensures that you’re protected in the event of a crash or accident.
A B0090 engine code can also be caused by:
  • An open or shorted sensor harness
  • A poor electrical connection to the sensor circuit

Common symptoms of the B0090 engine code

Besides a B0090 engine code, your vehicle will also activate the
airbag indicator light
when there is an issue with your driver’s seatbelt sensor.

How serious is the B0090 engine code? 

Because B0090 engine codes relate to the driver’s seatbelt, you need to have the problem inspected and resolved right away.
Though a faulty seatbelt sensor will not prevent you from driving your vehicle, you cannot depend on your driver’s seatbelt to function correctly during a collision. An unexpected mechanics bill may be unpleasant, but it’s far more preferable than being injured or killed due to an unreliable seatbelt.

Can I fix the B0090 engine code myself?

Dismantling and reassembling your driver’s seatbelt is a challenging endeavor. When you include the stakes for having it done right, fixing a B0090 DTC is something best left to a professional mechanic.

Inspecting the left frontal restraints sensor

If you’re confident of your mechanical skills and want to try fixing your B0090 DTC at home, follow these steps:
  • Inspect the left frontal restraints sensor’s wiring harness and connectors
  • Check for damaged or worn components
  • Look for broken, bent, pushed out, or corroded connector’s pins
If the engine code is still being displayed after your inspection, take your vehicle to a professional as soon as possible.

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