P06B0
Power Supply A Circuit/OpenP06B0 is a generic OBD-II powertrain diagnostic trouble code: Power Supply A Circuit/Open. 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 P06B0 means
P06B0 is an SAE generic ECM/PCM self-diagnostic code indicating that the internal power supply circuit designated 'A' inside the control module has detected an open circuit condition or a voltage that is absent when expected. Modern ECMs contain multiple internal voltage regulators that step down and isolate power for different processing cores, reference circuits, and communication buses. If the module's own monitoring circuitry cannot confirm that Power Supply A is present and within range, it stores P06B0.
Because this is an internal module fault, external wiring causes must be ruled out first — specifically, the main power and ground feeds to the ECM itself. A high-resistance ground, an intermittent supply voltage at the main ECM power relay, or excessive voltage drop under crank can all starve the internal regulator and mimic a true internal failure. Battery condition and charging system health are therefore first-line checks before considering module replacement.
If all external feeds and grounds test within specification and the code persists or returns immediately after clearing, an internal ECM failure is confirmed. On some platforms the code may also be accompanied by multiple other U- or P06xx codes as the failing internal supply destabilizes reference voltages across several subsystems. Replacement of the ECM — and reprogramming or relearning of any immobiliser, throttle position, or transmission adaptive data — is typically the final resolution.
Common causes
Most-frequently reported root causes when P06B0 is logged.
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1
High-resistance or corroded ECM chassis ground connection
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2
Intermittent or low voltage at the ECM main power relay output under load
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3
Weak or failing battery causing voltage sag during cranking that drops below the regulator's minimum input
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4
Damaged main ECM power supply wiring (chafing, rodent damage, melted insulation near exhaust)
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5
Failed charging system causing chronic undervoltage during operation
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6
Internal ECM voltage regulator failure
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7
Water or coolant intrusion into the ECM connector or module body
Symptoms drivers notice
How to diagnose P06B0
A typical diagnostic flow when this code is present.
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1
Load-test the battery and verify charging voltage is 13.8–14.7 V; replace battery or repair alternator if outside range
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2
Measure voltage drop across all ECM ground straps and power supply terminals under cranking load; more than 0.2 V drop indicates a resistance fault
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3
Inspect the ECM connector body and pins for corrosion, pushed-back terminals, or signs of moisture ingress; clean or repair as needed
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4
Inspect the ECM main power relay and its socket; test relay coil resistance and switching voltage
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5
Clear the code and attempt to reproduce; if P06B0 returns immediately with all external circuits confirmed good, the ECM internal regulator has failed
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6
Check for any available TSBs or updated ECM calibrations for the specific platform before ordering a replacement module
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7
Replace and reprogram ECM per OEM procedure; perform any required relearn procedures (throttle body, transmission, immobiliser)
Vehicles where we've handled P06B0
Platforms in our catalogue with confirmed P06B0 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 a bad battery really cause P06B0?
Yes. If the battery voltage sags below the ECM's internal regulator minimum (often around 9–10 V) during cranking, the internal Power Supply A circuit can drop out momentarily and log the code. Always load-test the battery as the first step.
How do I know if the ECM itself is faulty versus the wiring?
Perform a complete voltage-drop test on every ECM power and ground pin. If all feeds and grounds are within spec, the battery is healthy, and the code returns immediately after clearing with the engine running, the internal regulator has failed and the ECM needs replacement.
Will P06B0 clear itself after the underlying issue is fixed?
It should clear after a certain number of successful drive cycles once the fault is resolved. However, because it is an internal module code, it is best practice to clear it manually with a scan tool after the repair and confirm it does not return.
Do I need to reprogram a replacement ECM?
In almost all cases, yes. Replacement ECMs require VIN programming and in many cases immobiliser synchronisation, throttle position relearn, and transmission adaptive resets. Check your vehicle's OEM service procedure before installing a used or remanufactured unit.
Disabling P06B0 in software
RaceTune can permanently disable P06B0 — 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 P06B0 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
- Bosch EDC17CP44 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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