What is a serial communication link?

It's the data network — most commonly a CAN bus — that lets your vehicle's control modules talk to each other and lets the PCM's internal processors exchange data. Instead of running a separate wire for every signal, modules send digital messages over a shared pair of wires. P0600 means the PCM detected that one of those links failed: expected messages stopped arriving, or the link is open, shorted, or internally disrupted.

Is P0600 the PCM's fault?

Usually not directly. Because P0600 is a communication fault, the most common causes are the things that carry and power the data: damaged bus wiring, corroded connectors, bad grounds, water intrusion, and low battery voltage. A failing module elsewhere on the network can also trip it. Genuine internal PCM failure is possible but should be confirmed only after the wiring, grounds, and power supply check out — replacing the PCM first is an expensive guess.

Can I drive with P0600?

It depends on what the lost communication affects. If the engine runs normally and the only symptom is the check engine light, you can drive while you arrange diagnosis. But if the transmission is in limp mode, the ABS or stability lights are on, or shifting is harsh, have it diagnosed promptly — those systems are degraded and the fault can escalate. If the vehicle won't start or repeatedly drops into reduced power, get it to a shop rather than risk being stranded.

Why do I have U-codes along with P0600?

That combination is common and actually helpful. P0600 says 'a serial link failed,' while U-series codes (like U0100 for lost communication with the ECM/PCM) name the specific module or bus that dropped offline. Diagnosing the U-codes usually points you straight to the affected circuit or module, which is more precise than chasing P0600 by itself. Read them together and start with the most specific code.

OBD-II trouble code

P0600: Serial Communication Link Malfunction

The powertrain control module lost communication over one of the serial data links it uses to talk to other modules or internal processors. It's a network/communication fault rather than a sensor problem — wiring, connectors, grounds, and power supply are the usual culprits before the PCM itself.

Quick facts

System: Powertrain
Category: PCM / Electronics
Severity: High severity
Drivable: Usually safe to drive short-term
Repair cost range: $100 – $1,500
DIY difficulty: Shop recommended

What does P0600 mean?

Modern vehicles are networks on wheels. The powertrain control module doesn't run the engine in isolation — it constantly exchanges data with the transmission controller, ABS module, body control module, instrument cluster, and often its own internal co-processors, all over serial data links such as CAN. P0600 sets when the PCM detects that one of those serial communication links has failed: messages it expects aren't arriving, a link is open or shorted, or an internal communication channel inside the module has dropped out.

Because P0600 is a communication fault, the most productive places to look are the things that carry and power those messages: the data bus wiring, connectors, grounds, and the PCM's power supply. A chafed CAN wire, a corroded connector, a poor ground, or chronic low battery voltage can all interrupt serial communication and trip P0600. It frequently appears alongside U-series network codes (U0001, U0100, and similar) that point more precisely at which module or bus dropped offline — reading those together usually tells a clearer story than P0600 alone.

The practical impact depends on which link failed. If the PCM can't talk to the transmission or ABS controller, you may get limp mode, harsh or defaulted shifting, a disabled stability system, or warning lights across the dash. In some cases the engine still runs normally and the only sign is the check engine light. Either way, P0600 shouldn't be ignored: communication faults can be intermittent at first and then escalate, and a link that drops at the wrong moment can leave you in reduced-power mode unexpectedly.

Common causes

Damaged or chafed serial data bus (CAN) wiring
Corroded, loose, or backed-out connector on the data bus or at the PCM
Poor or corroded ground shared by networked modules
Chronic low battery voltage or a failing battery disrupting communication
Water intrusion at a module connector or the PCM housing
A failed module on the bus dragging the network down
Corrupted PCM software (sometimes resolvable with a reflash)
Internal PCM fault affecting its communication processor (confirm wiring first)

Symptoms

Check engine light on with P0600 stored
Multiple U-series communication codes set at the same time
Transmission in limp mode or shifting harshly / defaulting
ABS, traction control, or stability warning lights illuminated
Instrument cluster gauges or warning lights behaving erratically
Possible no-start or hard-start condition
Sometimes intermittent — code clears and returns

Diagnostic steps

1.Read all stored codes, not just P0600. Accompanying U-codes (U0001, U0100, etc.) often identify exactly which module or bus dropped communication and should be diagnosed first.
2.Check battery voltage and the condition of every battery terminal and major ground. Low voltage and bad grounds are common, cheap causes of communication faults.
3.Inspect the data bus wiring and connectors for chafing, corrosion, water intrusion, and backed-out terminals, paying attention to harness sections that flex or route near heat.
4.Measure CAN bus resistance and signal integrity at the diagnostic connector to confirm the network is healthy.
5.Disconnect suspect modules one at a time (where safe) to see whether a single failing module is dragging the bus down.
6.Check for a manufacturer technical service bulletin or reflash that addresses P0600 on your specific vehicle.
7.Only after wiring, grounds, power, and bus integrity check out should the PCM itself be suspected.

Repair cost

$100 – $1,500

A wiring, connector, ground, or battery repair — the most common real fix — runs $100-$400. Diagnosing an intermittent network fault can add shop time because it requires tracing the bus. A PCM reflash is $80-$250 if a TSB applies. Replacing a failed module on the network varies widely by module. PCM replacement including programming runs roughly $800-$1,500. Because P0600 is a communication fault, replacing the PCM should be a last resort after the wiring and power supply are confirmed good.

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DIY vs shop

Leave this one to a qualified shop. It typically involves emissions-critical components, refrigerant handling, or other work that requires manufacturer-grade tooling, training, or certification. DIY attempts often produce a more expensive problem than the original code.