P0A79 critical

Motor/Generator B Phase U Short to Ground

The P0A79 code means the vehicle's onboard diagnostic system has detected: Motor/Generator B Phase U Short to Ground. This is a critical severity code.

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Keep driving?: No -- stop driving
DIY difficulty: hard
Estimated cost: $1,500 - $5,000 (parts and labor)

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Common Symptoms

Check Engine Light on
Hybrid system warning light
Vehicle may enter limp mode or shut down
Electric motor vibration or loss of power

Probable Causes (Ranked by Likelihood)

Motor winding insulation breakdown Very High
Failed inverter power transistor (IGBT) High
Damaged motor phase wiring Moderate
Contamination or moisture in motor housing Low

Step-by-Step Diagnostic Procedure

Read all stored codes and freeze frame data with a hybrid-capable scan tool.
Inspect accessible wiring and connectors related to the affected circuit.
Test the affected component using manufacturer-specific diagnostic procedures.
Clear codes and perform a test drive while monitoring related parameters with the scan tool.

Frequently Asked Questions

What does P0A79 mean?

P0A79 indicates a fault with the motor/generator b phase u short to ground in a hybrid or electric vehicle. This code requires diagnosis by a hybrid-certified technician with proper high-voltage safety equipment.

Is P0A79 dangerous?

This is a critical fault. Do not attempt to work on high-voltage components without proper training. Have the vehicle towed to a qualified hybrid repair facility if the system is disabled.

Can a regular mechanic fix P0A79?

This code requires a technician certified in hybrid vehicle repair with proper high-voltage safety training and insulated tools. Not all repair shops have the equipment to diagnose hybrid-specific faults.