What Does P0B0C Mean?
The powertrain control module has detected a hydraulic leakage condition in the auxiliary transmission fluid pump system. This means transmission fluid is escaping from the pump housing, seals, fittings, or lines, resulting in reduced fluid pressure and potential external fluid loss. Hydraulic leakage reduces the pump's ability to maintain adequate fluid flow to the transmission during engine-off operation and can lead to low transmission fluid levels over time.
Common Causes
35%
Worn or damaged pump housing seals allowing external leakage
20%
Cracked or porous pump housing from thermal stress or manufacturing defect
20%
Loose or damaged fluid line fittings at the pump inlet or outlet
15%
Internal pump gear wear causing excessive bypass (internal leakage) without external drip
10%
Damaged fluid line or hose between the pump and transmission
Diagnostic Steps
1
Visually inspect the auxiliary pump area for external fluid leaks. Clean the area thoroughly first, then run the pump and check for fresh fluid weeping from the housing, seals, or fittings.
2
Check the transmission fluid level. A low level combined with this code suggests an ongoing external leak that must be located and repaired.
3
If no external leak is visible, the code may indicate internal bypass leakage. Monitor fluid pressure output from the auxiliary pump (if a pressure test port is available) and compare with specification.
4
Inspect the fluid line connections at the pump inlet and outlet. Tighten fittings to specification and check for cracked or hardened O-rings at the connection points.
5
If the pump housing is cracked or porous, look for signs of fluid seeping through the casting itself. This is more common in aluminum housings subject to thermal cycling.
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
The powertrain control module has detected a hydraulic leakage condition in the auxiliary transmission fluid pump system. This means transmission fluid is escaping from the pump housing, seals, fittings, or lines, resulting in reduced fluid pressure and potential external fluid loss. Hydraulic leaka...
The most common cause of P0B0C (Auxiliary Transmission Fluid Pump Hydraulic Leakage) is: Worn or damaged pump housing seals allowing external leakage
Typical repair costs for P0B0C range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Transmission fluid leakage can lead to low fluid levels, which causes overheating and accelerated wear of transmission components. If the fluid drips onto hot exhaust components, it can create a fire risk. Monitor the fluid level closely and repair the leak before fluid loss becomes critical. The vehicle can be driven short distances with the engine running if the fluid level is adequate.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B0C to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Transmission Auxiliary Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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