B101D: How to Diagnose & Fix — ECU Hardware (Control Module Internal Hardware Performance)
4 vehicles · 4 makes · $100-$900 repair
How to diagnose and fix B101D: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
GMC Terrain · 2013–2019
The IntelliLink/MyLink touchscreen freezes and spontaneously reboots, losing control of radio, climate, navigation and Bluetooth, and often displays a black screen or a frozen backup-camera image. During a reboot, phone calls drop and the rear camera can go dark while in reverse - a visibility concern. Root causes include software glitches, outdated firmware, and occasionally loose display/camera wiring.
Common Symptoms
- Touchscreen freezes or reboots
- Black/blank infotainment screen
- Backup camera not working or shows frozen image
- Lost radio/Bluetooth/nav
- Dropped phone calls on reboot
How to Fix
Start with a software/firmware update at the dealer and a system reset (Home + Fast Forward held ~10s, or Return to Factory Settings). Persistent cases require reseating/repairing loose harness connectors or replacing the radio/display module or backup camera.
Sources for this issue (1)
Buick Encore GX · 2023–2025
On later Encore GX models the Lane Keep Assist with Lane Departure Warning system applies an inappropriate steering torque that pulls the vehicle across the centerline rather than back into the lane. NHTSA complaints describe a sudden, forceful takeover of the steering wheel toward oncoming traffic, requiring the driver to fight the system. CarComplaints lists Lane Assist as the leading reported problem on the 2025 model year. The behavior appears tied to camera misinterpretation of lane markings - faded lines, tar seams, construction striping, shadows and crest transitions - compounded by camera calibration that was never performed or was performed incorrectly after a windshield replacement.
Common Symptoms
- Steering wheel jerks or grips forcefully toward the centerline
- Vehicle steers toward oncoming traffic without driver input
- Repeated false lane departure alerts on clearly marked roads
- System activates over tar seams or old lane markings
- Behavior worsened after a windshield replacement
How to Fix
Have the front camera module recalibrated - this is mandatory after any windshield replacement and is the most common root cause of biased lane centering. Verify the camera's mounting bracket is fully seated and the windshield in front of it is free of distortion or an aftermarket tint strip, and confirm the vehicle is on the latest camera/ADAS module software, since GM addresses lane-centering behavior through calibration files. Check tire pressures and alignment, because a mechanical pull the system compensates for changes its torque output. Until it is corrected, Lane Keep Assist can be disabled through the vehicle settings menu; report the incident to NHTSA, since ADAS defects are only investigated when complaint volume builds.
Sources for this issue (2)
Chevrolet Bolt EUV · 2022–2022
GM TSB 19-NA-076, revised February 2023, lists the 2022 Chevrolet Bolt EUV among the affected vehicles. On shifting into Reverse the center display shows either a blue screen with a 'Service Rear Vision System' message or a black screen with a red triangle and a crossed-out camera icon, with no rearward image at all. The condition can persist for an entire power cycle and typically clears only after the A11 radio enters and exits a sleep cycle. GM attributes it to software anomalies in the Video Processing Module or the rear camera, not to a wiring failure. Because FMVSS 111 requires a rearview image, a car that intermittently shows no reverse camera is a real safety defect and not just an annoyance. On EUVs equipped with the standard rear view camera (RPO UVB) the radio stores history DTC B395A with symptom bytes 08, 72 and 3A.
Common Symptoms
- Blue screen with 'Service Rear Vision System' when selecting Reverse
- Black screen with red triangle and crossed-out camera icon
- Camera works again after the car sits and the radio sleeps
- Condition can appear about 25 minutes after startup when idling
How to Fix
Diagnosis is DTC-driven and GM is emphatic that the Video Processing Module should usually NOT be replaced. On surround/trailer camera builds (UV2/UVI/UVS) with B101D symptom byte 3C or 39 in the VPM, or B395A 08/72/3A in the radio, reprogram the Video Processing Module (K157) - reflashing reduces the sensitivity of the B101D trip. On standard rear-view-camera builds (UVB), if the A11 radio has stored all three B395A symptom bytes 08, 72 AND 3A and the blue screen persists through a power cycle, replace the rearview camera. If all three bytes are not present the bulletin does not apply and the shop should keep diagnosing. Covered under the bumper-to-bumper warranty on cars still inside 3 years/36,000 miles.
Sources for this issue (1)
Cadillac XTS · 2013–2019
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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?
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).
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?
Repair costs for B101D range from $100 to $900, depending on the vehicle and root cause.
Which vehicles are affected by B101D?
Au7o has documented B101D across 4 vehicle models from 4 manufacturers: Buick, Cadillac, Chevrolet, GMC.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.