High Voltage Power Supply Circuit Failure
Indicates a malfunction in the high voltage power supply circuit.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The car's computer is not getting the proper high voltage it needs to operate some systems, which can lead to major performance issues or a no-start condition.
What the computer is actually seeing
The onboard computer monitors the voltage in the high voltage power supply circuit. If it detects a voltage out of the expected range due to failure of the circuit, it triggers the C1288 code.
What a healthy reading looks like
You should see around 50-100 volts in the high voltage supply circuit during normal operation.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Check the condition of all wiring and connectors associated with the high voltage power supply circuit. Look for corrosion, loose connections, or damage.
- 22. Inspect the high voltage battery for any physical damage or signs of wear.
- 33. Measure the voltage in the high voltage power supply circuit. It should be within 50-100 volts. If not, there may be a fault in the power supply.
- 44. If voltage is within range, check for any hybrid system faults if applicable, using a scan tool to read further codes.
- 55. If no other codes are present and all checks pass, you may need to replace the high voltage battery or power supply based on manufacturer's specifications.
Common causes
- Faulty high voltage battery or power supply
- Wiring issues in the high voltage circuit
- Faulty connectors
- Problems with the vehicle's hybrid system (if applicable)
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
No, it's not safe to drive; the vehicle may lose power or not start at all.
Will this issue come back after I fix it?
If the underlying cause is not addressed, the code may return.
Why does this code sometimes appear with other codes?
It often indicates a larger issue with the high voltage system, so related codes may point to specific failures.
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