P0A79 — Drive Motor "B" Inverter Performance

P0A79 — Drive Motor "B" Inverter Performance. A fault in the sensor and actuator circuits. The car is usually drivable while you plan the repair. Typical causes: faulty sensor or actuator of the affected circuit, poor ground connection, corroded, loose or damaged connector.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P0A79 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the drive motor "B" inverter performance for damage, corrosion, chafing or poor contact.
Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P0A79 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P0A79 (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Control module repair: $300–$1,000; Repair wiring or connectors: $80–$250. Overall, fixing P0A79 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What does OBD2 code P0A79 mean?

How much does it cost to fix P0A79?

Replace the faulty sensor or actuator — $150–$500; Control module repair — $300–$1,000; Repair wiring or connectors — $80–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

What are the symptoms of P0A79?

Drivers most often notice: the affected system operates intermittently or not at all, Check Engine Light on, increased fuel consumption in some cases, possible limp mode depending on the affected component.

How do I diagnose P0A79 myself?

Start with a scan: confirm P0A79, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the sensor and actuator circuits, and verify the suspect component against live data before buying parts.

Is it safe to drive with P0A79?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

P0A79 indicates a performance problem with Drive Motor "B" inverter circuitry. This component sits inside the hybrid or electric vehicle's powertrain control module and acts as the electronic bridge between the battery pack and the drive motor. When functioning normally, the inverter converts direct current from the high-voltage battery into alternating current that spins the motor, and reverses that process during regenerative braking. The engine control unit monitors voltage signals, temperature readings, and switching frequencies through multiple sensor and actuator circuits woven throughout the inverter assembly.

When self-diagnostics identify readings that fall outside acceptable ranges, the module logs P0A79. One anomalous reading won't trigger this code—the fault must appear consistently under specific operating conditions before the check engine light illuminates. The stored freeze frame data captures engine load, RPM, coolant temperature, and vehicle speed at the moment of failure, which proves invaluable during diagnosis because it pinpoints exactly when and where the problem occurred. Understanding this behavior helps technicians reproduce the fault conditions rather than chasing phantom issues.

Symptoms of P0A79

Persistent or intermittent illumination of the check engine light
Drive Motor "B" operates erratically or fails to engage entirely
Noticeable increase in fuel consumption compared to normal driving patterns
Vehicle may enter reduced-power limp mode depending on which inverter circuit is affected
Reduced or complete loss of regenerative braking capability in hybrid models
Unusual sounds or hesitation from the electric drivetrain during acceleration
In rare cases, complete refusal to start in hybrid vehicles

Common Causes

The inverter performance fault typically traces back to one of these sources:

Damaged wiring or connectors — open circuits, short-to-ground events, or corroded terminals in the inverter wiring harness represent the most frequent culprits
Blown fuse — a failed fuse protecting the inverter power supply interrupts proper circuit operation
Insufficient ground connection — corroded, loose, or damaged ground straps cause voltage irregularities that trigger performance codes
Failed sensor or actuator — temperature sensors, current sensors, or gate drivers within the inverter assembly can malfunction
Internal inverter module failure — the power electronics inside the inverter housing itself can degrade over time
Coolant circulation problems — many hybrid inverters rely on liquid cooling; low coolant or a failing pump causes thermal protection shutdowns
Control module software issues — outdated calibration files occasionally produce false performance faults

How to Diagnose P0A79

Start diagnosis by confirming the code exists and gathering data:

Connect a quality OBD2 scanner, retrieve P0A79, and record all available freeze frame information including engine load, RPM, coolant temperature, and vehicle speed at the time of failure.
Scan for additional diagnostic trouble codes. Related P0xxx codes often point directly to the failing component. Check manufacturer technical service bulletins using your VIN at nhtsa.gov or the automaker's website—many inverter issues have documented software updates or known fixes.
Perform a thorough visual inspection of the inverter wiring harness and connectors. Look for damaged insulation, broken wires hidden under tape, corrosion buildup, and any signs of connector looseness or moisture intrusion.
Test electrical integrity at the inverter connector: verify reference voltage supply is present, confirm ground resistance is below 5 ohms, and validate signal circuit continuity.
Conduct a wiggle test on the harness while monitoring live data parameters. Any signal dropout, fluctuation, or erratic readings indicate intermittent wiring faults that require repair.
Clear the code and perform a complete drive cycle that replicates the freeze frame conditions. If P0A79 returns, the fault is confirmed and component-level testing should proceed.

Repair Options

Repairs should follow a logical sequence from least to most expensive:

Repair Type	Parts Cost	Labor Cost	Total
Wiring harness repair or connector replacement	$80–$150	$100–$150	$180–$300
Sensor or actuator replacement	$150–$350	$100–$200	$250–$550
Control module repair or replacement	$300–$700	$150–$350	$450–$1,050
Full inverter assembly replacement	$800–$2,500	$200–$500	$1,000–$3,000

Cost Breakdown

The total invoice for addressing P0A79 typically falls between $180 and $1,050 when using independent repair shops. Most situations involve wiring defects or failed sensors—both relatively affordable fixes compared to inverter module replacement. Control module repair or replacement occupies the middle ground. Always pursue accurate diagnosis before purchasing major components; the priciest scenario rarely represents the actual problem, and unnecessary parts purchases inflate costs unnecessarily.

Can You Drive with P0A79?

In most vehicles equipped with this code, driving remains possible though you may notice diminished electric motor response, reduced fuel economy, or limited hybrid functionality. The vehicle typically avoids complete shutdown unless the inverter fails entirely. However, treat this code as urgent if accompanied by stalling, failure to start, or warnings affecting brakes or steering—these conditions demand immediate professional attention. Otherwise, schedule diagnostic evaluation within one to two weeks to prevent potential roadside breakdowns.