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U138F00 — Clock synchronization failure
Clock synchronization failure. The Taycan, 911 (992), Panamera (971), Panamera (972) and Cayenne report this code; below is which control unit sets it on each model and how to read and clear it.
Which models and control units set U138F00
How to read and clear U138F00
- Plug a standard ENET (Ethernet-to-OBD) cable into your Porsche's OBD port and your Mac or Windows PC.
- Open STEUER14, pick your car and run a fault scan: every control unit is read, and U138F00 shows with its status, its full description and the freeze frame when the unit stores one.
- Fix the cause first, then clear the fault memory and scan again to check it stays away. Reading and clearing fault codes is free on every control unit.
More about fault memory in the manual →
Download STEUER14 — free fault readingOther codes of the DC/DC Converter
| U122D00 | Ethernet databus branch 2, No communication |
| U12C800 | MAC address conflict in Ethernet switch branch 1 |
| U12C900 | MAC address conflict in Ethernet switch branch 2 |
| U12CA00 | MAC address conflict in Ethernet switch branch 3 |
| U12CB00 | MAC address conflict in Ethernet switch branch 4 |
| U12D000 | IPv6 address conflict |
| U139000 | Clock synchronization master, branch 1, invalid number |
| U139100 | Clock synchronization master, branch 2, invalid number |
| U13E300 | CONCLUSION Identification, implausible |
| U140000 | Function restriction – supply voltage too low |
| U140100 | Function restriction – supply voltage too high |
| U140800 | Internal voltage measurement, Implausible signal |
All 200 codes of this control unit →
Fault names come from the manufacturer's diagnostic data. STEUER14 is independent and not affiliated with Porsche AG. A code tells you what a control unit detected, not always which part failed — check wiring, supply voltage and related codes before replacing parts. STEUER14 shows each fault's full description, status and freeze frame on the car.