2009 Mazda MX-5 OBD2 Code B1942 Airbag Crash Sensor #2 Feed/Return Circuit Open

B1942 code definition

A B1942 code means that your 2009 Mazda MX-5 's onboard diagnostic system has registered a trouble code after detecting a discrepancy in the voltages to two terminals in the airbag circuit.

What the B1942 code means

Air bag sensors are designed to monitor the severity of a crash event. If a crash event is serious enough, the sensor will send a signal to the restraints control module (RCM), deploying the driver's side air bag. Air bag systems are designed to perform self-diagnostics. Voltage at terminal #17 of the diagnostic monitor connector is supposed to stay at 9-11 volts. Circuit #617 is connected to Circuit #624, at the right front impact sensor. If voltage at terminal #2 drops below the voltage at terminal #17, a B1942 code will be set.

What causes the B1942 code?

• Open circuit at terminal #617 or #624
• Open circuit in right front impact sensor
• Corrosion at airbag sensor
• Failed airbag sensor

What are the symptoms of the B1942 code?

• Flashing or illuminated airbag lamp on dash

How does a mechanic diagnose the B1942 code?

• Using a good quality code reader/scanner, check for any airbag-related trouble codes. B1941. B1943, B1944 and B1945 may accompany this trouble code.
• A factory wiring diagram will also be very handy for this diagnosis and repair.
• With the ignition in ON position and headlamp switch OFF, connect the scanner and check for trouble codes.
• Locate driver's side front impact sensor. On many Ford 2009 Mazda MX-5 s, the sensor is located near the hood latch or radiator core support.
• Check connectors, wiring and crimps for an intermittent problem. Perform a wiggle test.
• Check airbag sensor for corrosion, damage, dirt.
• 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 driver's side front impact sensor.
• Clear diagnostic codes and test drive 2009 Mazda MX-5 to see if codes return.

Common mistakes when diagnosing the B1942 code

As with many codes, technicians often jump ahead on a B1942 code without doing a proper process of elimination and end up replacing parts unnecessarily. More often than not, a B1942 code is due to corroded or damaged wiring or connectors, or a failed driver's side front airbag sensor.

How serious is the B1942 code?

A B1942 code can result in the airbag not deploying in a collision.

What repairs can fix the B1942 code?

• Replacement of driver's side front crash sensor
• Replace/repair of wiring and connectors

Additional comments for consideration regarding the B1942 code

On many Ford 2009 Mazda MX-5 s, the airbag light is designed to flash in sequence, alerting the driver to a trouble code. In this instance, four flashes, followed by a pause, then followed by two more flashes, indicates trouble code B1942. Any airbag-related work might be best left up to a professional. Accidental deployment of the airbag can result in serious injury.

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