What does it mean?
B1572 is a Body (airbags, seat belts, body electronics) fault code. It indicates: Door Ajar LR Circuit Open .
Symptoms
- Cluster never shows the left rear door as open, even when it is standing wide open
- Interior lamps do not come on when that door is opened
- Alarm arms with the door open, which leaves the vehicle unsecured
- Convenience features that depend on door status, such as auto-lock or approach lighting, stop working for that door
- The code stays current no matter how many times the door is cycled
Likely causes
- Broken wire in the left rear door hinge boot, the classic failure from repeated flexing
- Door ajar switch contacts inside the latch corroded to a permanently open state
- Connector unplugged or a terminal backed out after door trim or speaker work
- Poor or missing ground return for the ajar switch
- Latch replaced with a version that does not carry the ajar switch, leaving the circuit open
- Module input open internally
- Corrosion in a body-side connector along the rear door circuit
How to fix it
- Watch the door ajar status in live data while working the latch by hand with a screwdriver, so the door position is not a variable
- Jumper the ajar circuit to ground at the latch connector: if the module then reports the door open, the fault is in the latch switch
- Check continuity end to end through the hinge boot with the door open and then closed, to catch a wire that only breaks when flexed
- Inspect the connectors for corrosion, spread terminals and pins pushed back into the housing
- Verify the switch ground return with a voltage drop test rather than a simple continuity check
- Replace the latch assembly if its internal switch measures open in both positions
- Only after wiring and latch are proven good, check the module input and its connector