P0600: Serial Communication Link Malfunction
Key takeaways
- P0600 means a control module, usually the engine or transmission computer, detected a fault in a serial data link it depends on, either between processors inside the module or between it and another module.
- Drive short trips only: the car may go into reduced power or the transmission into limp mode; if it stalls or won't accelerate, have it towed.
- Check for a software update first, then the battery, grounds and connectors; the module should be the last thing replaced.
- Bulletins from Ford, Land Rover and Mercedes-Benz name P0600: a 2021 F-150 3.3L software update, and transmission-module cases with a gearbox fault message or limp-home mode.
- A replacement engine computer runs $800–$1,800 plus programming, so rule out the cheaper causes first.
What P0600 means
One of your car’s computers lost a data link it can’t work without. Scanners call it “Serial Communication Link Malfunction.” Many engine and transmission computers contain two processors: a main one that runs the engine or gearbox and a monitoring one that double-checks it. They talk over an internal serial link, and some modules also rely on a dedicated link to a partner module. When messages on that link stop, arrive corrupted or fall out of step, the module stores P0600.
The code doesn’t always mean the module is broken. Software bugs, low or unstable supply voltage, a bad ground and a damaged connector or harness can all break the link. And the module that stores P0600 isn’t always the engine computer; on some cars it’s the transmission computer.
Is it safe to drive?
Short trips only. When a module can’t trust its own internal data, it plays safe: the engine may drop into reduced power, the throttle may be limited, and the transmission may lock into one gear in limp mode. That’s why P0600 rates high even when the car seems normal.
The answer becomes no if the car stalls, won’t accelerate, or the transmission won’t shift out of one gear on the road. A stall at speed takes away power steering and brake assist; have it towed instead. If it drives normally, keep trips short and local until it’s checked. See can I drive with the check engine light on for the general rules.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Module software needing an update | A bulletin covers your make, model and year; shop checks the software level | $100–$200 |
| Low or unstable voltage (weak battery, charging fault) | Battery and charging test; P0562 stored too | $150–$350 for a battery |
| Loose or corroded battery terminals or module grounds | Voltage drop test at the grounds and the module connector | $20–$120 |
| Damaged wiring, bad crimp or water in a module connector | Inspect and test the connector and harness; on some cars the harness inside the transmission | $100–$250; internal transmission harness $300–$1,200 |
| Failed transmission computer (when the TCM stored the code) | All-module scan shows P0600 in the TCM; power, ground and software good | $500–$1,500 programmed |
| Failed engine computer | Updates, power, ground and connector all good; code returns | $800–$1,800 plus programming |
What to check first
- Scan every module, not just the engine. Find out which module stored P0600 and what other codes came with it.
- Check for a software update or bulletin. This comes before any part. The bulletins show a clear pattern: Ford reprograms the engine computer on 2021 F-150 trucks with the 3.3L engine that store P0600 with P060B or P0607, while Land Rover (2014–2015 Range Rover and Evoque) and Mercedes-Benz (2014 E400 Hybrid) cover P0600 in the transmission computer with a gearbox fault message or limp-home mode, one of them traced to a bad crimp in the internal transmission harness.
- Test the battery and charging system. A healthy battery rests near 12.6 volts, running voltage around 13.5 to 14.7.
- Clean and tighten the terminals and module grounds, and check the module connectors for water or corrosion.
- Clear it once and see if it returns. A one-time P0600 after a jump start or battery change may not come back.
- Replace the module last, and only a unit programmed to your car’s VIN.
6 owner complaints filed with NHTSA mention P0600, one each on six different models from Dodge, Chrysler, BMW, Honda, Mercedes-Benz and Ford. That’s too few to show a pattern; they’re owner reports, not confirmed defects.
What it costs
The cheap outcome is cleaned terminals or a tightened ground, $20–$120. The common outcome is a software update at $100–$200, or a battery at $150–$350. The expensive outcome is a replacement module: $500–$1,500 for a transmission computer, or $800–$1,800 plus programming for an engine computer. A $100–$180 diagnosis that checks software and voltage first is how you avoid buying a module that didn’t need replacing.
Related codes
P0600 often appears with other internal-module codes: P0606 (processor fault), P0607 (control module performance) and P0601 (memory checksum error). P0562 points to low voltage first. If other modules also log U0100, the engine computer has dropped off the network entirely, which is a wiring or power problem more often than a failed module.
What owners report to NHTSA
6 complaints filed with NHTSA mention P0600, 6 of them since 2015, across 6 different models. The component owners most often filed it under: engine.
Manufacturer service bulletins that name P0600
5 technical service bulletins and manufacturer communications filed with NHTSA mention P0600, from 3 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- FORD F-150 (2021), bulletin 10189791: Some 2021 F-150 vehicles equipped with a 3.3L Duratec engine and built on or before 02-Mar-2021 may experience an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P060B, P0600 and/or P060…
- LAND ROVER RANGE ROVER EVOQUE (2014, 2015), bulletin 10105428: "SITUATION: A 'GEARBOX FAULT' MESSAGE MAY BE DISPLAYED ON THE INSTRUMENT CLUSTER ALONG WITH ONE OR MORE OF THE FOLLOWING DIAGNOSTIC TROUBLE CODES (DTC) STORED IN THE TRANSMISSION CONTROL MODULE (TCM): P0600-04, P0710-27,…
- LAND ROVER RANGE ROVER (2014, 2015), bulletin 10117005: Situation: A 'Gearbox fault' message may be displayed on the Instrument Cluster along with one or more of the following Diagnostic Trouble Codes (DTC) stored in the Transmission Control Module (TCM): P0600-04, P0710-27, …
- MERCEDES-BENZ E400 HYBRID (2014), bulletin 10057728: XENTRY: TRANSMISSION COMPLAINTS IN COMBINATION WITH FAULT CODE P060C00/ P0600 THE SYMPTOMS INCLUDE THE TRANSMISSION SWITCHING TO LIMP- HOME MODE AND DISPLAY MESSAGE. *LJ
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Is P0600 the same as P0606?
They're close relatives. P0606 means the module's processor failed its own self-check. P0600 means a serial data link the module relies on failed, often the link between two processors inside the same module. Both are usually checked the same way: software, voltage, grounds, then the module.
Can a weak battery cause P0600?
It can. Low or unstable voltage can make the processors in a module lose sync or reset, and the link check fails. If P0562 (system voltage low) is stored too, or the code appeared after a jump start, test the battery and charging system first.
Which module set P0600?
Usually the engine computer, but not always. Land Rover and Mercedes-Benz bulletins cover P0600 stored in the transmission control module. A shop scan of all modules shows which one stored it, and that decides where to look.
Can I clear P0600 and keep driving?
You can clear it once to see if it returns, especially after battery work. If it comes back, or the car goes into reduced power, limp mode or stalls, get it checked before relying on it.