B101D on Cadillac: How to Diagnose & Fix
ECU Hardware (Control Module Internal Hardware Performance)
1 Cadillac model · 1 documented issue · $150-$500 repair
B101D on Cadillac by model: symptoms, diagnosis and fix
The Safety Alert Seat uses haptic (vibration) motors in the left and right seat bolsters to pulse warnings for lane departure, blind spot, and forward collision. The motor in one bolster can fail, or its wire can break where it enters the motor, so that side stops pulsing. Because GM ties this hardware into the driver-assist suite, a failed seat motor frequently also triggers a 'Service Driver Assist System' message.
Common Symptoms
- Service Driver Assist System message
- Only one seat bolster pulses for lane-departure alerts
- Seat vibration alert missing on one side
How to Fix
Confirm the dead side by triggering lane-departure to each side; if only one bolster pulses, the opposite motor/wire has failed. Replace the affected seat haptic vibration motor (left or right bumper-alert motor) and repair the broken wire at the motor entry. As a stopgap, owners can switch Alert Type to 'beeps' in the menu to restore audible warnings.
Sources for this issue (2)
B101D code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B101D mean on a Cadillac?
B101D stands for "ECU Hardware (Control Module Internal Hardware Performance)." General Motors body-code definition. When power-up is commanded, the control module runs an internal self-test that requires only battery voltage, ignition voltage and ground; that test runs even when supply voltage is outside the normal operating range. B101D sets when the module detects an internal hardware malfunction during that self-test — the failure is inside the ECU itself, not in an external sensor or actuator. The two-character symptom suffix (e.g. B101D-00, -31, -39, -3B, -F0) narrows which internal element failed. Because this code can be stored by any GM body module, the affected function depends on which module reported it (e.g. a Power Steering Control Module for a lane-keep/steering complaint, a Seat Module for a Safety Alert Seat complaint). On Cadillac it is documented across 1 model: XTS.
What are the most common causes of B101D?
The most common causes of B101D are: Internal failure of the reporting control module (ECU hardware fault) — the module is normally replaced and programmed, Corrupt or incomplete software/calibration in the module after a failed SPS programming event, Severe under- or over-voltage events, jump-start spikes or a failing battery stressing module internals, Water intrusion or corrosion inside the module housing, Poor power/ground supply to the module causing repeated resets. The specific cause varies by vehicle.
How much does it cost to fix B101D on a Cadillac?
Published repair estimates on Cadillac range from $150 to $500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.