What Does P06B3 Mean?
The 5-volt sensor power supply circuit "B" from the PCM is open or not providing the correct reference voltage to the sensors it feeds. Circuit B is a separate 5V supply from circuit A, typically powering a different group of sensors (such as the camshaft position sensor, oil pressure sensor, or secondary throttle position sensor). Multiple sensor codes may accompany this fault.
Safety Warning
Loss of the 5V reference B circuit disables multiple engine sensors, causing severe drivability issues and potential stalling. Do not drive the vehicle until the circuit is restored — engine stall risk is significant.
Common Causes
35%
Shorted sensor on the 5V reference B circuit pulling the supply line down and triggering open-circuit protection
25%
Broken or chafed wire on the 5V reference B supply circuit
20%
PCM internal 5V reference regulator failure on the B circuit
15%
Connector damage or corrosion at the PCM or a sensor on the B circuit
5%
Water intrusion into a connector on the reference B circuit causing a short
Diagnostic Steps
1
Identify which sensors are on the 5V reference B circuit using the vehicle-specific wiring diagram — this varies by manufacturer and model year.
2
Measure the 5V reference voltage at each sensor on the B circuit — if all read 0V, the fault is at the PCM output or in the common supply wire.
3
Disconnect sensors one at a time on the B reference circuit while monitoring voltage at the PCM output — voltage returning to 5V identifies the shorted sensor.
4
Inspect the wiring harness from the PCM to all sensors on the B circuit for damage, paying attention to areas near moving parts or heat sources.
5
If voltage remains absent from the PCM connector with all sensors disconnected, the internal 5V regulator for circuit B has failed — PCM replacement is required.
Estimated Repair Cost
$75 - $1,200
Parts + labor, varies by vehicle and location
The 5-volt sensor power supply circuit "B" from the PCM is open or not providing the correct reference voltage to the sensors it feeds. Circuit B is a separate 5V supply from circuit A, typically powering a different group of sensors (such as the camshaft position sensor, oil pressure sensor, or sec...
The most common cause of P06B3 (Sensor Power Supply "B" Circuit/Open) is: Shorted sensor on the 5V reference B circuit pulling the supply line down and triggering open-circuit protection
Typical repair costs for P06B3 range from $75 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of the 5V reference B circuit disables multiple engine sensors, causing severe drivability issues and potential stalling. Do not drive the vehicle until the circuit is restored — engine stall risk is significant.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P06B3 to identify the root cause.
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Quick Info
Category
Powertrain
System
Sensor Reference Voltage / Engine Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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