What Does P06B5 Mean?
The sensor power supply circuit "B" is reporting a voltage higher than the expected maximum threshold. The 5V reference B line is being driven above its normal operating range, which causes all sensors on this circuit to report values higher than actual. This can lead to rich fuel conditions, incorrect timing, and transmission shift quality issues.
Common Causes
35%
PCM internal 5V regulator malfunction on the B circuit outputting excessive voltage
30%
Short between the 5V reference B wire and a 12V power source in the harness
20%
Open or high-resistance ground return path for sensors on the B circuit
10%
Improper wiring repair or aftermarket modification feeding voltage into the B reference
5%
Alternator overvoltage condition causing all PCM internal references to run high
Diagnostic Steps
1
Measure the 5V reference B voltage at the PCM connector — document the actual reading and compare to the 4.95V-5.05V specification.
2
Disconnect all sensors on the B circuit and recheck the PCM output — if voltage normalizes, a sensor with a partial short to power is feeding voltage back into the line.
3
Inspect the harness for locations where the 5V reference B wire runs near 12V supply wires — look for insulation damage or improper splices.
4
Verify the sensor ground/return circuit has less than 0.1V drop under load; a floating ground will cause the reference to appear high.
5
Check the charging system output voltage — confirm it is between 13.5V and 14.7V. Overvoltage can skew internal PCM references.
Estimated Repair Cost
$75 - $1,200
Parts + labor, varies by vehicle and location
The sensor power supply circuit "B" is reporting a voltage higher than the expected maximum threshold. The 5V reference B line is being driven above its normal operating range, which causes all sensors on this circuit to report values higher than actual. This can lead to rich fuel conditions, incorr...
The most common cause of P06B5 (Sensor Power Supply "B" Circuit High) is: PCM internal 5V regulator malfunction on the B circuit outputting excessive voltage
Typical repair costs for P06B5 range from $75 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
High sensor reference voltage causes over-reporting of sensor values, potentially leading to fuel system issues and catalytic converter damage from incorrect air-fuel ratios. Diagnose promptly to prevent secondary damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P06B5 to identify the root cause.
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Quick Info
Category
Powertrain
System
Sensor Reference Voltage / Engine Control
Difficulty
Type
Generic (SAE)
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