What Does P06B1 Mean?
The sensor power supply circuit "A" is reporting a voltage lower than the minimum expected threshold (typically below 4.5V when it should be a stable 5.0V). This circuit provides the reference voltage that multiple engine sensors rely on for accurate readings. The driver may experience rough running, hesitation, stalling, and multiple sensor-related warning codes.
Common Causes
40%
One sensor on the 5V reference A circuit has an internal short to ground pulling the reference voltage low
25%
Wiring short to ground on the 5V reference A supply wire
20%
PCM internal 5V voltage regulator degradation on the A supply
10%
Connector pin corrosion or high-resistance connection causing voltage drop
5%
Excessive current draw from an aftermarket device tapped into the reference circuit
Diagnostic Steps
1
Measure the 5V reference A voltage at the PCM connector with a DVOM — compare to the specification of 4.95V-5.05V.
2
If voltage is low at the PCM output, disconnect all sensors on the A reference circuit and recheck — if voltage returns to 5V, reconnect sensors one at a time to identify the shorted component.
3
If voltage remains low with all sensors disconnected, inspect the harness for a short to ground by measuring resistance from the 5V reference wire to chassis ground (should be open/infinite).
4
Check for corroded or water-damaged connectors, particularly inline splice connectors that may be hidden under intake or valve cover area.
5
If the 5V reference is low at the PCM even with nothing connected, the PCM internal regulator has failed and the module needs replacement.
Estimated Repair Cost
$75 - $1,200
Parts + labor, varies by vehicle and location
The sensor power supply circuit "A" is reporting a voltage lower than the minimum expected threshold (typically below 4.5V when it should be a stable 5.0V). This circuit provides the reference voltage that multiple engine sensors rely on for accurate readings. The driver may experience rough running...
The most common cause of P06B1 (Sensor Power Supply "A" Circuit Low) is: One sensor on the 5V reference A circuit has an internal short to ground pulling the reference voltage low
Typical repair costs for P06B1 range from $75 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Low reference voltage causes all sensors on this circuit to report inaccurate readings, leading to poor fuel mixture, misfires, and potential stalling. Avoid driving until diagnosed — the engine may stall unexpectedly.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P06B1 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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