P06B1
Sensor Reference Voltage B Circuit/OpenP06B1 is a generic OBD-II powertrain diagnostic trouble code: Sensor Reference Voltage B 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 P06B1 means
P06B1 is stored when the PCM or associated control module detects an open circuit or an out-of-range voltage on sensor reference voltage circuit B. Many sensors in the engine management system share a 5-volt reference supply provided by the module. This reference is typically divided into named circuits (A, B, C) to facilitate fault isolation; circuit B covers a specific subset of sensors as defined by the manufacturer.
When the reference voltage is absent or incorrect, every sensor on that shared circuit will read incorrectly, causing the module to see multiple implausible signals simultaneously. This often generates a cascade of additional DTCs for MAP, throttle position, or other sensors alongside P06B1. Identifying and resolving the reference circuit fault first is essential because it is the root cause of the downstream sensor codes.
The most common cause is a short to ground anywhere on the reference voltage wire, which pulls the 5-volt rail down. This can originate from a damaged sensor, a chafed wire, or a faulty module internal regulator. Systematic isolation by unplugging sensors on circuit B one at a time while monitoring the reference voltage is the recommended diagnostic approach.
Common causes
Most-frequently reported root causes when P06B1 is logged.
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1
Short to ground on the 5-volt reference circuit B wiring.
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2
Failed sensor on circuit B with an internal short pulling the reference low.
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3
Chafed or pinched wiring harness contacting ground on the reference wire.
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4
Corroded connector creating a partial short or open in the reference supply.
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5
Open circuit B reference wire due to a broken or corroded conductor.
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6
Failed PCM internal 5-volt reference regulator for circuit B.
Symptoms drivers notice
How to diagnose P06B1
A typical diagnostic flow when this code is present.
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1
Record all DTCs; multiple sensor range or circuit codes alongside P06B1 strongly indicate a shared reference fault.
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2
Identify which sensors are powered by the circuit B 5-volt reference using the wiring diagram.
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3
Measure the circuit B reference voltage at the module connector with all sensors connected.
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4
Unplug sensors on circuit B one at a time and observe if the reference voltage recovers to 5 volts to isolate a shorted sensor.
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5
Inspect the circuit B reference wire along its entire length for chafing, pinches, or connector corrosion.
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6
If the reference voltage is normal with all sensors disconnected but the harness is intact, suspect the PCM internal regulator.
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7
Repair the identified short or open, reconnect sensors, clear codes, and verify all sensor readings are within range.
Vehicles where we've handled P06B1
Platforms in our catalogue with confirmed P06B1 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
Why do multiple sensor codes appear with P06B1?
Sensors sharing the same 5-volt reference circuit will all read incorrectly when that reference is pulled low or lost, generating cascade faults. P06B1 is typically the root cause code to resolve first.
How do I find which sensor is shorting the reference?
Unplug sensors on circuit B one at a time while monitoring the reference voltage. When the voltage recovers to 5 volts after unplugging a specific sensor, that sensor is the source of the short.
Can P06B1 cause a no-start condition?
Yes, if a critical sensor such as the MAP or crank sensor shares circuit B and loses its reference, the engine may not start or may stall during operation.
Is circuit B always the same sensors across vehicles?
No. The grouping of sensors on reference circuits A, B, and C is manufacturer-specific. Always consult the appropriate wiring diagram to identify which sensors are on circuit B for the specific vehicle.
Disabling P06B1 in software
RaceTune can permanently disable P06B1 — 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 P06B1 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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