P0600: Serial Communication Link
The engine control unit has detected a fault in a serial data link it uses.
High risk
The engine may run normally, stall or go into limp mode. Have it checked soon.
Short answer · Can I keep driving with P0600?
With caution. Depending on the car, other systems may lose data from the engine control unit. Have it checked soon.
What does P0600 mean?
P0600 means the engine control unit sees a fault on a serial communication link, on many cars the link between its own processors or between it and another control unit such as the transmission or immobiliser unit. Wiring or connector faults, a poor ground, low battery voltage or an internal control unit fault are typical causes.
What the car does when the code is set
The check engine light comes on. Depending on the fault, the car may run normally, go into limp mode with limited power or stall. Other warning lights may appear because of the internal fault.
How the system works
The engine control unit runs continuous self-tests on its processor, memory and internal communication. Many units have a second, independent monitoring processor that checks the main one, especially for safety-relevant functions such as the electronic throttle. If these checks find a mismatch, a memory error or a reset, the unit stores a processor fault code and may switch to a limp-home mode with limited power to keep the car controllable.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Internal control unit faultThe processor or memory self-test fails.
- Supply or ground problemLow voltage or a poor ground can make the self-test fail.
- Water damageMoisture inside the unit.
- Software faultAn interrupted update or a known software issue.
How it is diagnosed
- Check supply and grounds firstMeasure voltage and grounds at the control unit as in the service data.
- Check for software updatesManufacturers sometimes release updates that fix this code.
- Inspect the unit and connectorLook for water ingress and corrosion.
- Repair or replace with codingA replacement control unit usually needs programming and immobiliser matching.
Questions about P0600
Is P0600 the same as a U code?
They are related. U codes describe network messages between control units; P0600 is stored by the engine control unit itself. Check for other stored codes, which often show which link is affected.
Can a jump start damage the control unit?
Voltage spikes from incorrect jump starting can damage electronics. Always follow the manual's procedure.
Is a used control unit an option?
Only if it can be programmed to your car, including immobiliser data. A specialist can advise.