P0A73: Generator Phase V Current Low

P0A73 indicates that phase V of the hybrid generator delivers or reports too little current under load. No manufacturer documents P0A73 publicly. On inverters that measure only phases V and W, a low V reading has a knock-on effect: the calculated U current is wrong as well, so the generator torque control loses accuracy. A Caterpillar patent shows the logic for three-sensor systems, where a near-zero reading plus a violated zero-sum identifies the failed sensor; a Toyota patent compares a control sensor with a monitoring sensor and the current command. CARB requires circuit monitoring of electric drive components. P0A74 is the high side, P0A70 and P0A76 phases U and W, P0A72 the general code. Charging and engine start can suffer.

Symptoms

• Hybrid warning and MIL
• Engine runs more often, battery charge does not recover

Most likely causes

• Generator phase V current sensor reading near zero
• Generator phase V lead or terminal open
• Phase V switch in the generator inverter not conducting

What to check, in order

Start with the simplest. You can tick off each step.

1. Measure the voltage with the engine off and running
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Clean and tighten the terminals
4. Check the accessory belt
5. Run a battery load test
6. Check the alternator wiring

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0A73 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• A: Hybrid or air and fuel
• 73: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0A73?

If the battery warning light comes on, you could get stranded. Turn off electrical accessories and go straight to a repair shop.

What causes code P0A73?

The most common causes are: generator phase V current sensor reading near zero; generator phase V lead or terminal open; phase V switch in the generator inverter not conducting.

Related codes

• P0A72Generator Phase V Current
• P0A74Generator Phase V Current High
• P0A70Generator Phase U Current Low
• P0A76Generator Phase W Current Low
• P0A6ADrive Motor B Phase V Current Low

Sources

• patents.google.com: en
• patents.google.com: en
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.