2009 Mazda MX-5 OBD2 Code B1945 Airbag Crash Sensor #2 Ground Circuit Open

B1945 code definition

A B1945 code means that your 2009 Mazda MX-5 's onboard diagnostic system has detected an open circuit condition in the airbag circuit, and has registered a trouble code.

What the B1945 code means

Crash sensor monitors are set to register the severity of a crash event. If the impact is severe enough, the sensor will trigger the Restraints Control Module (RCM) and deploy the passenger side air bag. The RCM monitors the two-wire current loop for the passenger side crash sensor and will register if a signal is out of expected range. When the RCM detects an out of range signal for the passenger side crash sensor, that will indicate a sensor communication fault and the RCM will store trouble code B1945.

What causes the B1945 code?

• Damaged wiring on circuit 1263 (wh)
• Damaged wiring on circuit 1264 (bn)
• Damaged passenger side crash sensor

What are the symptoms of the B1945 code?

• Flashing or illuminated airbag lamp on dash

How does a mechanic diagnose the B1945 code?

• Using a good quality code reader/scanner, check for any airbag-related trouble codes. B1942. B1943, B1944 and B1941 may accompany this trouble code.
• A factory wiring diagram will also be necessary for this diagnosis and repair.
• With the ignition in ON position and headlamp switch OFF, connect the scanner and check for trouble codes.
• Locate right front impact sensor. Check connectors, wiring and crimps for an intermittent problem. Perform a wiggle test.
• Disconnect air bag diagnostic monitor. Measure resistance between terminals #2 and #17 of diagnostic monitor connector. NOTE: disconnecting the diagnostic monitor deactivates the entire airbag system.
• If resistance is less than 2 ohms, replace diagnostic monitor.
• If resistance is greater than 2 ohms, disconnect right front impact sensor from harness.
• Measure resistance between the sensor connector's pink/orange and yellow/white wires.
• Resistance should be less than 2 ohms. Locate and repair any open circuits found in #617 or #624.
• If resistance is greater than 2 ohms, replace entire right front impact sensor.
  
• Clear diagnostic codes and test drive 2009 Mazda MX-5 to see if codes return.

Common mistakes when diagnosing the B1945 code

As with many codes, technicians often jump ahead on a B1945 code without doing a proper process of elimination and end up replacing parts unnecessarily. In most cases, a B1945 code is due to damaged, corroded or loose wiring or terminals on the passenger side crash sensor. The sensor is located near the passenger side headlight or radiator core support.

How serious is the B1945 code?

A B1945 code can result in the airbag not deploying in a collision.

What repairs can fix the B1945 code?

• Replacement of right front crash sensor
• Replace/repair of wiring and connectors

Additional comments for consideration regarding the B1945 code

Any airbag-related work might be best left up to a professional. Accidental deployment of the airbag can result in serious injury. On Ford 2009 Mazda MX-5 s, the airbag malfunction lamp will self-diagnose for the driver by blinking in sequence. For example, on a B1945 code the lamp will blink four times, pause, then blink five times to denote “45.”

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