Serial Communication Link Malfunction
P0600 means Serial Communication Link Malfunction. Learn the likely symptoms, common causes, and a safe diagnostic order before replacing parts.
What you may notice
Symptoms
- 01Warning lights or multiple stored codes
- 02Slow, failed, or intermittent starting
- 03Modules resetting or communication dropping out
- 04Electrical accessories behaving unpredictably
Where to look first
Common causes
- 01Battery, charging-system, relay, fuse, or power-distribution fault
- 02Loose ground, damaged connector, or high-resistance wiring
- 03Short to voltage, short to ground, or open circuit
- 04Module communication or internal control fault
A sensible sequence
Best diagnostic order
- 01Save all module codes before disconnecting power
- 02Check battery state, charging behavior, fuses, and main grounds
- 03Inspect and load-test the affected power, ground, relay, or communication circuit
- 04Check for voltage drop and intermittent connection problems
- 05Clear codes and verify operation through several start and drive cycles
Step by step
What to check and repair
- 01Test battery condition and charging voltage under the correct conditions
- 02Inspect fuses, relays, grounds, connectors, and harness routing
- 03Measure voltage drop instead of relying only on continuity
- 04Diagnose network or module faults with the vehicle wiring diagram
Read the signals
Live-data clues
Control-module voltage
- Typical behavior
- Voltage should remain within the manufacturer operating range without abrupt dropouts
- Possible clue
- Spikes or drops can create several unrelated-looking codes
Command and circuit status
- Typical behavior
- Commanded state and feedback should agree
- Possible clue
- A mismatch helps locate a relay, load, wiring, or module-driver fault
| Parameter | Typical behavior | What it can suggest |
|---|---|---|
| Control-module voltage | Voltage should remain within the manufacturer operating range without abrupt dropouts | Spikes or drops can create several unrelated-looking codes |
| Command and circuit status | Commanded state and feedback should agree | A mismatch helps locate a relay, load, wiring, or module-driver fault |
What P0600 means
P0600 is a generic powertrain diagnostic trouble code defined as “Serial Communication Link Malfunction.” The vehicle control module stored it after the monitored circuit or system failed its expected test. The code identifies the area and failure type; it does not by itself prove that one named component must be replaced.
Diagnostic direction
Electrical codes should be diagnosed with the battery and charging system known to be stable. Low or excessive voltage can create misleading secondary codes across several modules.
Before clearing the code
Save stored, pending, and permanent codes plus freeze-frame data. Note the operating condition that set the code, inspect related connectors and wiring, and check vehicle-specific service information. After a verified repair, clear the code only when appropriate and repeat the enabling conditions to confirm that it does not return.