What does it mean?
B2124 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Ignition Run Control 1 Circuit Open .
Symptoms
- Memory reset function does not work and stored settings cannot be cleared
- Memory recall and store both behave unpredictably
- Accessories powered from the ignition run circuit drop out or never come on
- Engine may crank but the vehicle does not run correctly on affected applications
- Warning message in the cluster
- Code sets again immediately after clearing
Likely causes
- Reset switch mechanically jammed by trim pressure or a broken return spring
- Contamination inside the switch pack from a spilled drink or cleaning fluid
- Switch input wire shorted to ground so the module always sees a request
- Open circuit in the ignition run feed, from a blown fuse or a broken wire
- Burnt ignition switch contacts that no longer close in the run position
- Corroded connector at the memory module or the ignition switch
- Ground fault at the module distorting how inputs are read
- Module input stage failure, only after the wiring has been checked
How to fix it
- Look up the manufacturer definition and the correct pin for this vehicle
- Watch the reset switch state in live data with the switch untouched
- Remove the trim, free the switch and confirm it returns fully when released
- Unplug the switch and measure the input to ground, an open reading blames the switch, a grounded reading blames the harness
- For the ignition variant, check the fuses and perform a voltage drop test across the ignition switch in each position
- Check continuity of the run circuit from the switch to the module with both connectors off
- Repair the wiring, replace the switch or ignition switch as required
- Clear the code, cycle the key several times and confirm the fault does not return