Roewe Plug-in Hybrid DC-DC Converter (DCDC) Fault Diagnosis Guide

Fault Background

The Roewe plug-in hybrid (846 manual) DC/DC converter is located in the high-voltage distribution system (via interfaces such as HV001/HV002/HV007/HV012/HV013). It converts high-voltage battery pack energy into low-voltage system power. Fault levels are divided into four tiers: stop immediately for repair / limp home to shop / return to shop / no repair needed (follow maintenance). Almost all codes indicate "internal system fault, not involving external circuits," with highly quantified thresholds: output current >10A (P1D61) / >180A (P1D62), output voltage <3V±5% (P1D65) / >16.5V±2% (17:) or <8.5V±2% (16:) (P1D66), input voltage >440±5V / <215±5V (P1D68), coolant temperature >85℃ (P1D63), PCB temperature >105℃ (P1D64), discharge activation time >3s with input >55V (P1D67). History codes are cleared after 40 fault-free ignition cycles. This article is organized as a quick diagnostic guide.

Output Current Family

Action: Check converter connector installation position/harness/connector wear or corrosion → clear codes and retest → if it recurs, inspect/replace the DC/DC converter; for cover-open repairs, seek professional personnel.

Output Voltage and Input Voltage Family

• P1D65: Output voltage <3V±5% → SVS light + power-down; cleared when >6V±5%;
• P1D66 17: Output >16.5V±2% → SVS light + resume detection after power-cycled (cleared when ≤16.2±2%); P1D66 16: Output <8.5V±2% → SVS light + immediate automatic restart, every 2s, up to 5 times; if still not working, shutdown (cleared when ≥8.8±2%);
• P1D68 17:/16: Input voltage >440±5V / <215±5V — diagnosis goes to high-voltage side: check HV007 and vehicle harness connectors, verify voltage before testing high-voltage terminals.

Action: All are internal converter fault determinations; if codes recur after clearing and retesting → inspect/replace DC/DC.

Temperature Family (Coolant / PCB)

• P1D63 DC/DC coolant temperature >85℃ (cleared when <65℃) → power-down + SYS light; P1D64 PCB circuit board temperature >105℃ (cleared when <85℃) → power-down + SYS light;
• P1D6C 12:/11: PCB circuit board temperature sensor feedback abnormal → SVS light (converter remains powered).

Diagnostic path: Read "PEB coolant temperature" live data to see if reasonable (if not, replace coolant temperature sensor) → check coolant temperature sensor connector BY210 and vehicle control unit BY260 (loose/poor contact/twisted/corroded/contaminated/deformed) → check for low/contaminated coolant → measure BY210-1↔BY260-54, BY210-2↔BY260-73 resistance <5Ω (if out of range, check for open circuit/excessive resistance) → resistance to ground infinite (if out of range, check for short to ground) → if still reported, replace sensor/replace DC/DC.

The temperature sensor is powered by 5V from the vehicle control unit, and the coolant temperature signal is fed back to adjust the cooling system control in real time.

Sensor Feedback and Discharge Family

• P1D6B DC/DC output current sensor feedback abnormal / P1D6D output voltage sensor feedback abnormal → power-down + SVS light; cleared when feedback returns to normal;
• P1D67 Discharge activation time >3s with input voltage >55V (cleared when <3s and <55V) — active discharge circuit abnormal, pointing to converter internal.

Mode and Network Family

• P1D82 DC/DC request mode error / P1D83 when request invalid, default output 14.25V (protective constant voltage output);
• U0073 88: Powertrain high-speed CAN bus off — follow "high-speed CAN network integrity check" to check BY216-3 ↔ FA004-15 and other circuits; U0111/U0146/U0293 correspond to controller communication loss; U1562 supply voltage >16.5V±5% / U1563 supply voltage too low (e.g., <9V) — first check battery voltage and fuses; U1763/U1897/U191B network frame timeout types.

Safety Warnings

• This article is for technical reference. DC/DC repair involves high-voltage input (input threshold 215~440V) and must be performed by qualified technicians (electrician certificate + company training authorization) per OEM specifications.
• Before testing high-voltage circuits: ignition OFF, wait at least 5 minutes, operate the manual service disconnect switch to disconnect high-voltage battery power, disconnect the 12V battery negative terminal, and confirm no high voltage at terminals.
• Although the output low-voltage side is a 12V system, the restart strategy for P1D66 16: (5 times) and the 14.25V default output for P1D83 mean the converter will attempt self-recovery — when testing output, avoid the automatic restart cycle to prevent misjudgment.
• After replacing the DC/DC, perform module self-learning and adjustment, programming and coding as required.

Repair Insights

The biggest feature of the Roewe DCDC code table is "code means internal fault": except for the temperature family (P1D63/64/6C), most codes list only "DC/DC converter fault" as the possible cause, and the diagnostic steps are very short — visual inspection of connectors → clear codes and retest → if it recurs, replace DC/DC, with no repairable harness links, saving a lot of ineffective troubleshooting. Three numbers worth remembering: 10A (P1D61 power-down threshold — output current over 10A is considered internal overcurrent, directly powering down for protection), 16.5V/8.5V (output window upper/lower limits, with ±2% tolerance, clear thresholds with hysteresis to 16.2V/8.8V to prevent flapping), 440V/215V (input window, corresponding to the high-voltage battery pack's normal operating range of 260~410V). Behavioral details are also practical: P1D66 16: under-voltage causes the converter to "restart every 2s, up to 5 times, and only shuts down if still failing" — seeing periodic fluctuations when measuring output voltage is not a fault, it's self-recovery; P1D83 default constant voltage 14.25V when request invalid — this is the safety baseline output for the low-voltage system. Finally, the temperature family is the only path requiring harness work: BY210-1↔BY260-54, BY210-2↔BY260-73 <5Ω + infinite to ground, first judge the sensor circuit before suspecting the converter.

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【This article is for reference only】