BYD Han DM-p Adaptive Cruise Control (ACC/AEB) System Diagnostics and Radar Removal/Installation Guide

Fault Background

The Han DM-p cruise control system is a "perception → decision → execution" longitudinal and lateral assistance architecture, with three core functional layers: ICC Intelligent Cruise Control (including TJA/ICA, full-speed-range longitudinal + lateral assistance), ACC Adaptive Cruise Control (0–150 km/h fixed-speed cruise and automatic follow-to-stop control), and AEB Automatic Emergency Braking (seven sub-functions: safety distance warning, forward collision warning FAW, automatic warning braking AWB, hydraulic brake assist HBA, brake prefill BP, AEB, and brake boost assist BBA). The perception end is completed by the front millimeter-wave radar (MRR) + multi-function video controller assembly, while the execution end links EMS (powertrain), ESP (braking), and EPS (steering). The most critical lesson in field repair is calibration: the countermeasure for DTCs such as "radar installation angle error too large / radar module not calibrated" is always recalibrating the radar; after removing/installing the radar, the radar should not have obvious play when shaken left and right — if it is installed crooked, it will trigger a new round of calibration errors. This article organizes the three major functions, ECU terminals, DTCs, and radar removal/installation into a reference guide.

Three Major Functional Components

System components: front millimeter-wave radar (MRR), powertrain control system (EMS or vehicle control unit), braking system control unit (ESP), HMI (including instrument cluster and ACC stalk), combination switch, body control module, steering wheel angle sensor, and various mounting brackets.

ECU Terminal Inspection

For the front millimeter-wave radar pins (electrical equipment side), measure voltage and resistance according to the manual table:

• CAN FD high/low: connected to the multi-function video controller;
• Power pin: connected to power supply;
• If measurement results do not meet specifications → the wiring harness may be faulty; check the harness first before suspecting the radar module itself.

DTC Table (ISO15031-6)

Key rule: For DTCs involving "calibration," do not replace parts — recalibrate first; for DTCs involving "blockage," first check for physical obstructions in front of the radar.

Radar Removal and Installation

Removal:

1. Remove the front bumper first;
2. Use a Phillips screwdriver or electric wrench to remove the 3 cross-recessed pan head self-tapping screws with flat washers (Q2214816F62K), and take out the radar + radar bracket assembly as a unit;
3. Disconnect the connector between the radar and the mating harness;
4. Push the radar out from the bottom along the open slot of the radar bracket.

Installation:

1. Align the radar with the open slot of the radar bracket and press it in until it bottoms out;
2. Connect the connector between the radar and the mating harness;
3. Align the radar and bracket assembly with the front bumper screw boss positions, and secure the 3 mounting points with the cross-recessed pan head self-tapping screws with flat washers (Q2214816F62K);
4. After installation, shake the radar left and right — the radar module should not have obvious play.

Safety Warnings

• This article is a technical reference; cruise/driver assistance system repairs must be performed by certified personnel in accordance with OEM specifications. Readers who are not familiar with these procedures are strictly prohibited from performing the work themselves.
• After radar removal/installation, recalibration is mandatory; ACC/AEB longitudinal control is not reliable if the radar is uncalibrated or incorrectly calibrated, and the vehicle must not be delivered in that state.
• When removing the front bumper and working on the radar, take care to protect the connectors and wiring harness; the radar is a precision component — dropping, impacting, or striking it is prohibited.
• Observe driving safety during road tests; AEB function verification must be performed in a controlled environment.

Repair Insights

The field value of this cruise control manual is concentrated in the "calibration closed loop" and the "two mandatory checks." Calibration closed loop: the countermeasure for radar-related DTCs (installation angle error, module not calibrated) is recalibration rather than part replacement — removal/installation → press into the bracket slot to the bottom → secure the 3 mounting points → shake left and right to confirm no obvious play → recalibrate → road test verification; not a single step can be skipped; if installed crooked by even 1 degree, calibration will fail every time. Two mandatory checks: first, "obstructions" — the front bumper, license plate frame, mud/snow, and film can all cause the radar to report blockage-type DTCs; check physical obstructions before considering electrical faults; second, "terminals and wiring harness" — if the radar terminal voltage/resistance does not match specifications, check the harness first; if the CAN FD link to the multi-function video controller is broken, the fault will be incorrectly attributed to the radar module. On the functional side, remember one criterion: ACC is full-speed-range longitudinal control from 0 to 150 km/h, and AEB is the final active safety net (warning → braking intervention in stages) — when customers complain about "cruise not following the vehicle ahead" or "AEB false alarms," first distinguish the function, then check calibration and obstructions.

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【This article is for reference only】