P06B2
Power Supply A Circuit HighP06B2 is a generic OBD-II powertrain diagnostic trouble code: Power Supply A Circuit High. 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 P06B2 means
P06B2 is an SAE generic ECM/PCM self-diagnostic code indicating that Internal Control Module Power Supply A is measuring a voltage above its expected upper threshold. Unlike P06B0 (open/absent) or P06B1 (low), P06B2 specifically flags an over-voltage condition on the internal 'A' supply rail. The ECM's onboard regulator is designed to produce a tightly controlled internal voltage — typically 5 V or 3.3 V depending on architecture — and a high reading suggests either a regulator fault, a reference voltage anomaly, or an externally applied over-voltage reaching the module.
External causes to evaluate include charging system over-voltage (a failing voltage regulator in the alternator can push system voltage to 16 V or higher), installation of an aftermarket performance module or power adder that injects voltage onto a shared bus, and damaged wiring that has created a direct short from a higher-voltage supply rail to the ECM input. These should be eliminated before assuming the ECM itself is at fault, as operating an ECM under over-voltage conditions can permanently damage internal semiconductors.
If the charging system and all external circuits check out within specification and the code is persistent, an internal ECM regulator or monitoring circuit failure is the diagnosis. Over-voltage codes occasionally accompany physical damage inside the module from a prior spike event — for instance, from jump-starting with reversed cables or from a lightning-related surge — in which case the module will need replacement and programming even if the triggering event has passed.
Common causes
Most-frequently reported root causes when P06B2 is logged.
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1
Overcharging alternator or failed voltage regulator pushing system voltage above 15.5 V
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2
Reversed jump-start polarity or jump-start voltage spike damaging internal regulator
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3
Aftermarket tuning device or add-on module injecting voltage onto a shared ECM supply line
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4
Short from a higher-voltage circuit (e.g., ignition feed) to an ECM reference or signal wire
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5
Internal ECM voltage regulator failure producing runaway output voltage
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6
Damaged ECM connector allowing pin migration or cross-contact with an adjacent higher-voltage terminal
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7
Prior over-voltage event (lightning, welding with engine running) that damaged internal monitoring circuitry
Symptoms drivers notice
How to diagnose P06B2
A typical diagnostic flow when this code is present.
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1
Measure charging system voltage at the battery with engine running at 2,000 RPM; above 14.8 V sustained indicates alternator over-voltage — repair the charging system first
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2
Inspect battery terminals and main fusible links for signs of reversed polarity damage or heat discoloration
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3
Disconnect any aftermarket add-on modules or tuning devices and clear the code; if it does not return, the aftermarket device is the source
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4
Backprobe ECM power supply pins and compare measured voltage against OEM specification; identify any pin with voltage higher than specified
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5
Visually inspect the ECM connector for pushed-in or migrated pins, corrosion bridges, and heat damage
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6
If all external circuits are within specification and the code persists, the ECM internal regulator has failed and module replacement with reprogramming is required
Vehicles where we've handled P06B2
Platforms in our catalogue with confirmed P06B2 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
Is P06B2 more serious than P06B0?
Both are serious, but P06B2 (over-voltage) carries a higher risk of permanently damaging ECM internal semiconductors. An open supply (P06B0) may leave the module non-functional temporarily; sustained over-voltage can cause irreversible damage to processor cores and communication transceivers.
Can a bad alternator alone cause P06B2?
Yes. A failing alternator voltage regulator is one of the most common external causes. If it pushes charging voltage above roughly 15.5–16 V, the ECM's internal regulators may be overwhelmed and log an over-voltage fault. Always test the charging system before diagnosing the ECM.
I jump-started my car and now P06B2 is set — did I damage the ECM?
Possibly. If the jump-start was performed with reversed cables even briefly, a voltage spike in reverse polarity can destroy internal clamping diodes and regulators. Check all fuses and fusible links first, then have the ECM tested by a specialist before purchasing a replacement.
Will clearing P06B2 with a scan tool fix anything?
Clearing the code only removes the stored fault; it does not repair the underlying condition. If the root cause — over-voltage charging, a shorted wire, or a faulty ECM — is not addressed, the code will return immediately or on the next drive cycle.
Disabling P06B2 in software
RaceTune can permanently disable P06B2 — 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 P06B2 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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