OBD-II trouble code
P0606: PCM Processor Fault
The powertrain control module has detected an internal processor or memory fault — the computer that runs your engine has flagged a problem with itself. Rare across most platforms, but unusually common on certain Ford EcoBoost and Chrysler V6 engines where the cause is often a known PCM hardware defect.
Quick facts
- System
- Powertrain
- Category
- PCM / Electronics
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $1,800
- DIY difficulty
- Shop recommended
What does P0606 mean?
P0606 is one of the very few OBD codes where the engine computer is reporting a problem with itself rather than with a sensor or actuator. Modern PCMs run continuous self-diagnostics — every few seconds the processor runs checksum routines on its memory, validates that its internal voltage rails are within spec, and confirms that its co-processors and watchdog circuits are responding. When any of those internal checks fail repeatedly, the PCM sets P0606 and (depending on which subsystem failed) may enter a default operating mode or refuse to start the engine entirely.
Unlike most codes, P0606 doesn't have a long list of cheap causes to chase. It usually means one of three things: a corrupted software image (often resolvable with a PCM reflash at the dealer), an underlying power supply problem to the PCM (chronic low voltage, a marginal ground connection, or a recent jump-start with reverse polarity), or a genuine PCM hardware failure that requires replacement.
The platform pattern matters here. On Ford EcoBoost engines from roughly 2011-2017 — the 1.5L, 1.6L, 2.0L, and 3.5L variants — P0606 has been associated with a manufacturing defect in the PCM that produces this code intermittently and sometimes alongside other electrical complaints. There were extended warranty programs and class action settlements for some affected vehicles. If you own one of those engines and you're seeing P0606, check NHTSA recall lookups and class action coverage before paying for a $1,500 PCM replacement out of pocket. Similar patterns exist on some Chrysler 3.6L Pentastar engines.
Common causes
- Internal PCM hardware failure
- Corrupted PCM software image (resolvable with reflash)
- Chronic low battery voltage stressing the PCM
- Marginal or corroded PCM ground connection
- Reverse polarity jump-start damage
- Water intrusion at the PCM connector or housing
- Known Ford EcoBoost PCM defect (specific model years)
- Known Chrysler Pentastar 3.6L PCM issue (specific model years)
- Aftermarket tune or programming attempt that bricked the PCM
Symptoms
- Check engine light on with P0606 stored
- Engine may enter limp mode or default operating parameters
- Possible no-start condition if the fault is severe
- Other unrelated trouble codes may set simultaneously
- Cooling fan or other PCM-controlled accessories may behave erratically
- Sometimes intermittent — code clears and returns within days
- Possible communication errors with other modules (U-codes)
Diagnostic steps
- 1.Check the battery voltage and the condition of every battery terminal and major engine ground. A failing battery or corroded ground is the most common root cause of intermittent P0606 — and the cheapest fix by far.
- 2.Look up the vehicle in NHTSA recall lookup and a few model-specific forums. P0606 is a known issue on several Ford EcoBoost and Chrysler 3.6L platforms with potential warranty or class-action coverage.
- 3.Check for a manufacturer technical service bulletin matching your VIN. Some P0606 codes are software-only and resolve with a free dealer reflash.
- 4.Inspect the PCM connector and harness for water intrusion, corrosion, or pin damage.
- 5.Scan for other codes — multiple module communication errors (U-codes) plus P0606 often point at the same root cause: power supply or ground.
- 6.If all of the above check out, the next step is professional PCM diagnosis at the dealer or a module specialist. Don't replace the PCM as a first guess — it's expensive and not always the fault.
Repair cost
$100 – $1,800
Battery, terminal, or ground repair: $100-$300 and often resolves intermittent P0606. PCM reflash at the dealer: $80-$250 if a TSB applies, sometimes covered under powertrain warranty. PCM replacement: $800-$1,800 including programming — the module itself is $500-$1,200, with programming and core charge accounting for the rest. If your vehicle is under a recall or extended warranty for this code, the cost can drop to zero. Always check coverage first.
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Related repairs
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.