What Does P0B0B Mean?
The powertrain control module has detected that the supply voltage to the auxiliary transmission fluid pump motor exceeds the maximum safe operating limit. Overvoltage can damage the pump motor control module's electronic components, cause excessive motor speed, and generate overheating. This condition is often related to a charging system malfunction producing excessive voltage output.
Safety Warning
Overvoltage conditions can damage multiple electronic modules, not just the pump controller. If the charging system is overcharging, the battery may overheat or vent gases. Address the root cause immediately. Check all vehicle electrical systems for proper operation and inspect the battery for swelling or heat.
Common Causes
40%
Overcharging condition from a failed voltage regulator in the alternator or DC-DC converter
25%
Voltage spike from a load dump event (sudden disconnection of large electrical loads)
20%
Faulty supply voltage sensing circuit in the pump control module
10%
Poor battery connection causing voltage transients under varying load
5%
Aftermarket electrical accessories introducing voltage spikes
Diagnostic Steps
1
Measure system voltage at the battery terminals with the engine running. Normal is 13.5-14.8V. Readings consistently above 15V indicate an overcharging condition that must be addressed first.
2
Monitor system voltage with the scan tool under varying electrical loads (headlights, blower motor, heated seats). Voltage should remain stable — transient spikes above 16V indicate a regulation problem.
3
If system voltage is normal at the battery, measure voltage directly at the pump controller supply pins. A significantly higher reading at the module than at the battery suggests a wiring or sensing issue.
4
Check battery terminal connections for looseness or corrosion. A high-resistance battery connection can cause voltage spikes when loads cycle on and off.
5
Inspect for aftermarket electrical installations that may be back-feeding voltage into the pump supply circuit or causing system-wide voltage instability.
Estimated Repair Cost
$100 - $900
Parts + labor, varies by vehicle and location
The powertrain control module has detected that the supply voltage to the auxiliary transmission fluid pump motor exceeds the maximum safe operating limit. Overvoltage can damage the pump motor control module's electronic components, cause excessive motor speed, and generate overheating. This condit...
The most common cause of P0B0B (Auxiliary Transmission Fluid Pump Motor Supply Voltage Circuit High) is: Overcharging condition from a failed voltage regulator in the alternator or DC-DC converter
Typical repair costs for P0B0B range from $100 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Overvoltage conditions can damage multiple electronic modules, not just the pump controller. If the charging system is overcharging, the battery may overheat or vent gases. Address the root cause immediately. Check all vehicle electrical systems for proper operation and inspect the battery for swelling or heat.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B0B to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Transmission Auxiliary Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
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