Code
P0600
SEAT
P — Powertrain
PCM - no serial data
AI status
Completed
Completed
100%
Causes
- Open, short or intermittent wiring on CAN/serial communication lines (CAN H/CAN L)
- Damaged, corroded or loose connectors at PCM or junctions
- Failed PCM/module or internal processor fault
- Missing or blown fuse(s) or disabled power/ground to PCM
- Poor or missing ground(s) at chassis or engine
- Faulty termination resistor(s) on CAN bus (open/incorrect resistance)
Symptoms
- Multiple warning lights illuminated (engine, ABS, airbag, traction)
- No response from engine control functions via scan tool (no live data)
- Cruise control, immobiliser or instrument cluster not communicating or nonfunctional
- Intermittent or permanent no-start condition if PCM loses comms with other modules
- Erratic module behavior or random faults stored in multiple systems
What to check
- Confirm stored freeze frame and related DTCs with a capable scan tool
- Check battery voltage (should be ~12.4–12.8 V parked, ~13.5–14.5 V running)
- Inspect fuses and relays that supply PCM and communication bus power
- Visually inspect PCM connector and harness for corrosion, bent pins, water damage
- Check chassis and engine ground points; ensure tight, corrosion-free connections
- Measure termination resistance between CAN H and CAN L (with ignition off)
Signal parameters
- CAN (idle/recessive) voltage: CAN_H ≈ 2.5 V, CAN_L ≈ 2.5 V (measured to chassis ground)
- CAN differential (recessive): ≈ 0 V; dominant differential typically 1.5–2.5 V during frames
- Termination resistance between CAN_H and CAN_L (across the bus): ≈ 60 Ω (two 120 Ω terminators in parallel)
- Typical high-speed CAN bus data rates: 250 kbps or 500 kbps depending on vehicle circuit
- No-data condition: bus remains static at recessive voltages and oscilloscope shows no frames
Diagnostic algorithm
- Read and record all stored codes and freeze-frame data from all modules. Note other U-codes or communication faults.
- Verify battery condition and charging system. Recharge or replace battery if voltage is low and retest.
- Check and verify all fuses/relays related to PCM and communication buses. Replace any blown fuses.
- Visually inspect PCM connector, nearby splice points and wiring for damage, corrosion or water ingress. Repair as needed.
- Confirm ground points for engine/PCM are secure and have low resistance to chassis (use a DVM). Clean/tighten grounds as required.
- With ignition ON (engine off), measure CAN_H and CAN_L voltages at the PCM connector. Expect ~2.5 V each if bus intact.
- Measure resistance between CAN_H and CAN_L with ignition OFF. Expect ≈ 60 Ω. An open or very low resistance indicates wiring/termination issues.
- Use an oscilloscope or CAN bus analyzer at the PCM connector to observe activity. If no frames are present, isolate by disconnecting modules to find the segment causing the bus to go silent.
- Disconnect or isolate suspected shorted module(s) or aftermarket devices and retest bus activity. Repair harness faults found.
- If wiring and other modules check OK and PCM still does not communicate, attempt PCM reprogram/reflash per manufacturer procedure. If reflashing fails or PCM remains unresponsive, consider PCM replacement or repair.
- After repairs, clear codes and verify communication restored and that DTC P0600 does not return under normal operating conditions.
Likely causes
- Blown fuse or poor power/ground to PCM
- Open/short in CAN H or CAN L near PCM or at common junction
- Connector corrosion or bent pins at PCM harness
- Failed/locked PCM requiring reflash or replacement
- Failed module on same bus pulling the network down (short to ground/voltage)
Fault status
Status
P0600 — PCM no serial data: The PCM is not transmitting or receiving on the vehicle communication bus. Other modules report loss of communication with the PCM.
Repair difficulty: Medium
Diagnostic time: 1.5 - 3.0 hours
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