P0600🔧 Engine computer (PCM) communicationStop and fix promptly

P0600: Serial Communication Link Malfunction (Meaning, Causes, Fixes)

Reviewed 2026-10-26 · Based on 2 cited source(s)

What P0600 means

The powertrain control module (PCM, also called the engine control module or ECM) runs the fuel and ignition systems and shares data with other modules such as the transmission, ABS and traction control computers. RepairPal explains that the serial communication link is what lets these control modules 'talk' to each other, and P0600 sets when the PCM has lost communication with one or more of them. OBD-Codes.com describes it as a malfunction in the wiring link between the ECM and one of its supporting modules over the controller area network (CAN bus), and says the code sets when the ECM sees that loss of communication for eight consecutive starts. The code is generic to OBD-II vehicles (1996 and newer), but OBD-Codes.com notes some makes word it differently: Chrysler 'PCM Fault, SPI Communications', GM 'Loss of Serial Communication Link', Infiniti 'AT communication circuit malfunction' and Nissan 'ECM/TCM communication malfunction'. Search interest shows people look it up most for Ford, Mercedes, Subaru, Dodge and Jeep, so check technical service bulletins (TSBs) for your vehicle.

Severity: can I keep driving?

Stop and fix promptly

Get it checked right away. RepairPal rates P0600 'Urgent', meaning immediate action is needed because it can cause severe damage or put people at risk. Both sources list stalling or dying at a stop, rough running and improper shifting among the possible symptoms, because the engine computer may lose control of systems it normally runs. If the engine stalls, misfires badly or the transmission won't shift properly, stop driving and have it towed rather than risk losing power in traffic.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. A loose or corroded connector on the PCM or the module it lost contact with (OBD-Codes.com calls this more likely than a broken wire)
  2. A failed driver circuit inside the ECM, or a defective PCM (both sources)
  3. Poor grounds at the ECM, the other module or the data bus (both sources)
  4. Damaged data bus (CAN bus) wiring, shorted to ground or open (both sources)
  5. A defective output device controlled by the PCM or another module (RepairPal)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Read all stored codes and freeze frame data and write them down. Other codes stored alongside P0600 can point to the module or system that lost communication.
  2. Check the battery and charging system, and make sure the battery terminals and ground cables are clean and tight.
  3. Look over the connectors at the PCM and at the module named by any other codes for looseness, corrosion or bent pins, and the harness for chafing.
  4. Don't unplug the ECM and probe its terminals without the wiring diagram and pin values. OBD-Codes.com warns that probing the wrong terminal can destroy the ECM or the other module.
  5. Look up TSBs for your vehicle that mention P0600 or communication faults.

Typical fixes

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

  • OBD-Codes.com calls P0600 a commonly misdiagnosed code: a module that isn't being controlled can produce a misfire or other symptom that looks like an ignition or fuel injection fault, but the real problem is the loss of communication. RepairPal likewise lists ignition and fuel injection problems whose root cause is a defective PCM as common misdiagnoses.
  • OBD-Codes.com recommends a professional technician with a dealer-level scan tool that can monitor the modules and pin values live, and says most vehicles need a memory saver before the battery is disconnected; on some vehicles, if the ECM loses its memory, it won't start until reprogrammed at the dealer.
  • RepairPal says that if you replace a module, inspect all of that module's output devices and wiring for shorts first, or the new module will fail in short order. It also says to recreate the code-setting conditions on a test drive while watching engine load, throttle position, RPM and road speed, because P0600 can be hard to detect.
  • The sources lean differently on cause: OBD-Codes.com says experience shows a poor connection or failed ECM driver is the root cause and loose or corroded connectors are more likely than broken wires, while RepairPal puts a defective PCM at the top of its list.

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0600?

It's not a good idea. RepairPal rates P0600 'Urgent', and both sources list stalling, rough running and shifting problems among the possible symptoms. Have it diagnosed soon, and tow it if it stalls or runs badly.

Does P0600 mean I need a new PCM?

Not necessarily. OBD-Codes.com says a poor or corroded connection is more likely than a broken wire and points to connections and grounds first, though both sources say a failed PCM is possible.

Why does P0600 cause a misfire?

If the engine computer loses control of a module, such as the ignition control, that system can misbehave. OBD-Codes.com says this is why P0600 is often misdiagnosed as an ignition or fuel injector problem.

What codes are related to P0600?

RepairPal lists the internal control module codes P0601 through P0607 next to it, and U-codes such as U0100 (lost communication with the ECM/PCM) also deal with network communication.

Sources

  1. OBD-Codes.com: P0600 Serial Communication Link DTC
  2. RepairPal: P0600 Serial Communication Link (rated Urgent)

Last reviewed 2026-10-26. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.