Roewe Plug-in Hybrid VCU Fault Diagnosis Guide

Fault Background

The Roewe plug-in hybrid (846 manual) vehicle control unit (VCU) coordinates the vehicle via three high-speed CAN networks: PT CAN (powertrain) connects VCU, dynamic stability control module SCS, power electronics box PEB, shift control unit SCU, gateway, DC/DC, high-voltage battery pack ESS, airbag module SDM; HY CAN (hybrid system) connects PEB, VCU, on-board charger OBC, Ali system communication module TBOX, diagnostic interface, ESS; CH CAN (chassis) connects steering angle sensor SAS, gateway, headlamp leveling DHL, EPB. On VCU main connector BY260, PT CAN is pins 17/18, HY CAN is pins 55/56. The DTC system is organized by "set condition + threshold + terminal number", and history DTCs are automatically cleared after 40 wake/standby cycles. This article is organized as a quick reference guide by "sensor category → PWM/SPI drive feedback family → data invalid family → internal fault family → high-voltage related".

DTC Index Quick Reference

Sensor Category Diagnosis (Thresholds + Terminal Numbers)

Accelerator pedal (BY260-26 ↔ BY026-2 for sensor 1, BY260-27 ↔ BY026-1 for sensor 2): Disconnect BY260 and accelerator pedal sensor BY026, measure corresponding terminals—12: voltage >4.75V check for short to 5V supply or excessive resistance, 14: voltage <0.15V check for short to ground; if wiring is normal, replace sensor, then replace VCU if still reported.

Fast charge port temperature sensor (BY260-37 ↔ BY226-9 negative, BY260-36 ↔ BY226-7 positive): 11: voltage <0.1V check for short to ground/excessive resistance, 15: voltage >4.9V check for open circuit; if wiring normal, replace sensor, then replace VCU if still reported.

Coolant temperature sensor (BY260-73 ↔ BY210-2): 11: <0.068V, 15: >4.6V same path.

PWM/SPI Drive Feedback Family (Unified Pattern)

Cooling fan (P1B16~18, connector BY220), main relay (P1B44~46), OBC electronic lock lock (P1B50~52)/unlock (P1B53~55), cooling water pump relay (P1B60~62, fuse F39) five families share the same pattern:

1. Set conditions: PWM feedback signal out of range for 100ms (00:); feedback value <1% (11/13:); feedback value =100% (12:); SPI communication fault for 100ms (08:);
2. Use diagnostic scan tool to read relevant parameters or force output (e.g., "on-board charger electronic lock control"), observe whether actuator operates;
3. Check VCU wiring connector BY260 and corresponding actuator connector terminals (damage/corrosion/contamination/deformation);
4. Check corresponding fuse blown (e.g., water pump relay fuse F39), replace fuse if blown;
5. If wiring and fuse normal → test/replace actuator; if still reported → test/replace vehicle control unit.

Data Invalid Family and Internal Fault Family

Data invalid family: P1B1A (gateway reports EPB data invalid for 100ms, with U0417)/P1B1B (AC data invalid)/P1B1D (BCW data invalid)—first check connector connectivity, ignition OFF, vehicle stationary for more than 5 minutes then retest; P1B1F DCDC failure (with U0298/U0599) go to DCDC special. P1B76 (EPB data invalid function code 29) same path.

Internal fault family: ROM checksum (P1B26~28), watchdog (P1B29~2C), clock (P1B23/24), EEPROM (U0401), chip temperature rationality (P1B20/21)—all have no external wiring to check, clear codes and retest still reported → test/replace vehicle control unit.

High-Voltage Related Codes

• P1B31 Drive motor high-voltage request inhibited (10ms): Drive motor system reports serious fault, go to power drive system repair;
• P1B40 High-voltage battery pack output power limited: go to high-voltage battery pack ESS repair;
• P1B41/P1B42 High-voltage system insulation fault (with fast charger): go to high-voltage battery pack and fast charging system insulation test;
• P1B43 High-voltage interlock switch open: check high-voltage battery pack wiring connector BY216 and high-voltage distribution device interlock loop;
• P1B81/P1B82 Cooling fan control circuit voltage out of range: operate manual service disconnect switch to disconnect high-voltage battery power then disconnect relevant connectors for repair.

Safety Warnings

• This article is for technical reference. VCU and high-voltage system (PEB/ESS/OBC) repair must be performed by qualified technicians (electrician certificate + company training authorization) according to OEM specifications.
• For high-voltage battery pack inspections (P1B43, P1B81/82), first operate manual service disconnect switch to disconnect high-voltage battery power; for insulation faults (P1B41/42), wear insulating gloves throughout.
• After replacing VCU, complete configuration per module self-learning/programming and setup procedures; history DTCs are cleared after 40 wake/standby cycles, do not misjudge as "repaired".

Repair Insights

The most valuable part of the Roewe VCU code table is the "PWM/SPI drive feedback family" unified pattern—cooling fan, main relay, OBC electronic lock (lock/unlock two families), cooling water pump relay five actuators, DTC numbers are neatly uniform (P1B16~18, 44~46, 50~52, 53~55, 60~62), set conditions only four types: feedback out of range, <1%, =100%, SPI communication error, all judged by 100ms. Remember this set, any family code can apply the five-step "force output → check terminals → check fuse → replace actuator → replace VCU". For sensor category, remember three threshold groups: pedal 4.75V/0.15V (extreme 5.6V), fast charge port temperature 4.9V/0.1V, coolant temperature 4.6V/0.068V—all are upper/lower boundary voltages under 5V reference system, multimeter readings directly compare to table. Finally, three disciplines: data invalid family first let vehicle sit for 5min then retest (communication codes are often intermittent); internal fault family (ROM/watchdog/clock/EEPROM) has no wiring to check, directly replace VCU; history codes are cleared after 40 wake/standby cycles—after repair and clearing codes, when customer reports codes again, first count whether they are history codes.

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【This article is for reference only】