P0A08: The computer sees an open circuit on the status line from the DC/DC converter

DC/DC converter status circuit open

Severity: Inspect soon

The DC/DC converter charges the 12-volt system from the high-voltage battery, so a fault in its status circuit can mean poor 12-volt charging; owner reports with this code include a hybrid warning and lost power.

It gets more serious if:

Stop: Stop somewhere safe and arrange a tow if power drops, the hybrid or master warning appears with a stop message, or the 12-volt battery warning comes on, since the car can run down its 12-volt supply.

Safety-critical system: explanation only, no DIY steps. Source: how we rate severity

P0A08 in short

P0A08 means the hybrid computer sees an open circuit on the status line from the DC/DC converter, the unit that charges the 12-volt battery from the hybrid battery. Reported cases involve the inverter assembly and its cooling pump. Get it checked soon; the converter is high-voltage and not a DIY job.

The DC/DC converter steps the high-voltage hybrid battery down to 12 volts to run the lights, computers and accessories and keep the small battery charged. It sends a status signal to the control computer. P0A08 sets when that signal path looks open, as if a wire were broken or unplugged.

On Toyota hybrids the converter sits in the same assembly as the inverter. A 2012 Prius owner was told the code points to an inverter problem, and a 2006 Highlander Hybrid showed P0A08 together with P0A05 and P0A93 when the inverter cooling pump had failed. Those two cases are individual reports, not maker findings.

We found no maker bulletin for P0A08. Nissan bulletins that appear in a code search for it only use the code as a campaign label for an unrelated brake fluid flush, so they do not apply.

Everything in this circuit is part of the high-voltage system. Orange cables and connectors are not for owners to touch. Diagnosis belongs with a dealer or a hybrid-trained technician.

Most likely causes

Cause 1: Fault in the inverter and DC/DC converter assembly
Supported by vehicle data
Why it ranks here
On the 2012 Prius the owner was told the code indicates an inverter problem, and the converter shares the inverter assembly on Toyota hybrids. This is a single complaint, so it ranks as vehicle data and not as a confirmed fix.
What would change this
Rises if a dealer finds other inverter codes with it or the converter fails its checks. Falls if the wiring and cooling system are found at fault instead.
How to test the hybrid drive motor
Cause 2: Failed inverter cooling pump (seen with P0A05 and P0A93)
Supported by vehicle data
Why it ranks here
The 2006 Highlander Hybrid complaint stored P0A08 with P0A05 and P0A93 and the technician found the inverter water pump not working; replacing the pump was the repair reported.
What would change this
Rises if P0A05 or P0A93 are stored too, or the coolant level is low. Falls if the cooling codes are absent.
Cause 3: Open wire or loose connector in the status circuit
Possible — needs testing
Why it ranks here
The code definition is an open circuit in the converter status line, which a broken wire or poor connector would cause. No bulletin or complaint we found confirmed this on a specific vehicle.
What would change this
Rises if the circuit checks open at a dealer with the system made safe. Falls if the circuit is intact.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

Step 1: Read all stored codes with a scan tool, note any hybrid or master warnings, and check whether P0A05 or P0A93 (cooling) are stored too. Do not open or unplug anything in the hybrid system.
Low riskTool: OBD-II scan tool
- IfP0A05 or P0A93 are stored with P0A08
  It meansThe inverter cooling system is part of the picture.
  Points to: Failed inverter cooling pump (seen with P0A05 and P0A93)
- IfP0A08 is stored alone or with other converter codes
  It meansThe converter assembly or its circuit needs the maker's tests.
  Go to step 2
Step 2: Have a dealer or hybrid-trained technician test the DC/DC converter, its status circuit and the inverter cooling system with the maker's procedure.
Best left to a shopTool: factory scan tool and high-voltage safety equipment
Warning:High voltage: the battery pack, inverter, motors and orange cables carry hundreds of volts that can kill. Do not unplug, probe or touch them. This work needs a hybrid-trained technician who makes the system safe first.
- IfThe converter or inverter assembly fails its tests
  It meansThe assembly is repaired or replaced.
  Points to: Fault in the inverter and DC/DC converter assembly
- IfThe cooling pump or coolant level is at fault
  It meansThe cooling system is repaired.
  Points to: Failed inverter cooling pump (seen with P0A05 and P0A93)
- IfThe status circuit reads open
  It meansThe wiring or connector is repaired.
  Points to: Open wire or loose connector in the status circuit

Symptoms

Check engine or hybrid system warning light
12-volt battery or charging warning Gets more serious: stop and have it checked.
Vehicle will not go into Ready mode
Loss of power while driving Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

Inverter with converter assembly:High-voltage part. Ask the dealer for the test results before any part is ordered. Labor varies; get a quote.
Inverter coolant pump:Part of the inverter cooling circuit, serviced by a hybrid-trained technician. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

2006 · Highlander
Supported by vehicle data
Highlander Hybrid: one owner report stores P0A08 with P0A05 and P0A93 after a failed inverter cooling pump and loss of power.
2012 · Prius
Supported by vehicle data
One 2012 Prius owner saw a hybrid system warning with P0A08 and was told it indicated an inverter problem; no recall covered it.

All Hybrid and electric drive codes

P0A08 questions

Can I drive with P0A08?

Only to get it checked, and only if the car drives normally. If power drops, a stop message appears or the 12-volt battery warning shows, pull over safely and have it towed.

Can I fix P0A08 myself?

No. The DC/DC converter is part of the high-voltage system and needs a dealer or hybrid-trained technician.

Sources and review

Fault code P0A08 — TAT scan data library
NHTSA complaint ODI 1389530: 2012 Toyota Prius — NHTSA Office of Defects Investigation
NHTSA complaint ODI 1181794: 2006 Toyota Highlander Hybrid — NHTSA Office of Defects Investigation

Last reviewed: October 16, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

Severity: Inspect soon

Most likely causes

Cause 1: Fault in the inverter and DC/DC converter assembly

Cause 2: Failed inverter cooling pump (seen with P0A05 and P0A93)

Cause 3: Open wire or loose connector in the status circuit

What to test first

Step 1: Read all stored codes with a scan tool, note any hybrid or master warnings, and check whether P0A05 or P0A93 (cooling) are stored too. Do not open or unplug anything in the hybrid system.

Step 2: Have a dealer or hybrid-trained technician test the DC/DC converter, its status circuit and the inverter cooling system with the maker's procedure.