P0606
PCM Processor FaultP0606 is a generic OBD-II powertrain diagnostic trouble code: PCM Processor Fault. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0606 means
P0606 is an SAE generic powertrain code indicating that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an internal processor fault. The control module continuously monitors its own processor performance and integrity; when the self-diagnostic routines identify an error that exceeds calibrated thresholds, P0606 is set and the MIL is illuminated. Because the fault originates inside the control module itself, it is often accompanied by a cluster of secondary codes from subsystems (ABS, TCM, BCM) that share the Controller Area Network (CAN) bus.
The most common root causes are external to the module: a degraded power supply, a blown fuse or faulty relay feeding the ECM/PCM, or corroded/broken ground straps that cause reference-voltage instability inside the processor. Open or shorted wiring in the CAN harness can also corrupt communications in a way the module reports as an internal processor error. Physical damage to the module from water ingress, heat, or collision impact is a less frequent but definitive cause.
Diagnosis should always begin with a thorough inspection of power supply circuits, fuses, relays, and all chassis/engine ground connections before condemning the ECM/PCM itself. Replacing a control module without ruling out wiring and supply faults will typically result in repeat failures. If all external circuits test within specification and the code returns immediately after clearing, the ECM/PCM requires replacement and vehicle-specific reprogramming.
Common causes
Most-frequently reported root causes when P0606 is logged.
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1
Faulty or degraded ECM/PCM power supply relay
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2
Blown ECM/PCM power supply fuse
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3
Loose, corroded, or broken ECM/PCM ground strap or ground wire
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4
Open or short circuit in the CAN bus wiring harness
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5
Water ingress, heat damage, or physical impact to the ECM/PCM
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6
Internal ECM/PCM processor or memory failure
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7
Low or unstable battery/charging system voltage causing reference instability
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8
Damaged wiring connector or terminal at the ECM/PCM harness plug
Symptoms drivers notice
How to diagnose P0606
A typical diagnostic flow when this code is present.
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1
Retrieve all stored DTCs and document them; note any CAN-related or multi-system codes that may indicate a bus or supply fault rather than an isolated PCM failure
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2
Inspect all ECM/PCM power supply fuses and relays; replace any blown fuses and trace the circuit for the underlying short before re-fusing
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3
Check all ECM/PCM chassis and engine ground connections for tightness, corrosion, and continuity; measure ground resistance with a DVOM (should be near 0 Ω)
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4
Verify battery voltage (12.4–12.7 V key-off) and charging system output (13.8–14.7 V at idle); correct any supply or charging fault before proceeding
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5
Inspect the ECM/PCM harness connector and module housing for signs of water intrusion, corrosion, heat damage, or pin-back
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6
Clear the code, confirm all supply and ground circuits test within specification, and road-test; if P0606 returns immediately with no external fault found, the ECM/PCM processor has failed and requires replacement with vehicle-specific programming
Vehicles where we've handled P0606
Platforms in our catalogue with confirmed P0606 coverage.
Related powertrain codes
- P0600 — Serial Communication Link Malfunction
- P0601 — Internal Control Module Memory Check Sum Error
- P0602 — Control Module Programming Error
- P0603 — Internal Control Module Keep Alive Memory (KAM) Error
- P0604 — Internal Control Module Random Access Memory (RAM) Error
- P0605 — Internal Control Module Read Only Memory (ROM) Error
Frequently asked questions
Can I still drive with a P0606 code?
Driving is not recommended. P0606 signals an internal control-module processor fault that can cause stalling, loss of power, or a complete no-start condition. The vehicle should be diagnosed and repaired before regular use.
Will clearing the code fix the problem?
No. Clearing P0606 without repairing the underlying fault will only cause the code to return, often immediately. The root cause — whether a bad ground, blown fuse, or failed ECM/PCM — must be corrected first.
Does P0606 always mean I need a new ECM/PCM?
Not always. A significant percentage of P0606 cases are caused by external faults such as corroded grounds, a failed power relay, or unstable battery voltage. Always test the power and ground supply circuits thoroughly before replacing the module, as an unresolved external fault will destroy a new module as well.
Does replacing the ECM/PCM require reprogramming?
Yes. A replacement ECM/PCM must be programmed with the correct calibration data for the specific vehicle (VIN, options, and software version). This typically requires a dealer scan tool or a qualified shop with OEM-level programming capability; the module will not function correctly without it.
Disabling P0606 in software
RaceTune can permanently disable P0606 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P0606 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C74 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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