Toyota Prius Unable to drive, no ‘Ready’ Mode – Fault Code P3004

Toyota Prius P3004 – High Voltage Power Resource

This vehicle was recovered into us as a non-start, no drive. The High Voltage system could not be switched ‘on’ (no ‘Ready’ mode).

The dash did light up though – ignition ‘on’.

We always carry out the obvious – belt and braces – checks in a bid not to miss anything and also to aid in getting our minds into the job.

• The 12V battery was acceptable. We supported it with our batt support machine as best working practice anyway.
• The brake pedal switch was working. The car needs needs to see a depressed brake pedal in order to achieve Ready mode.

We carried out an initial global scan of the vehicle to gain further direction.

The obvious fault code was P3004-131 – High Voltage Power Resource.

What did this mean? What was triggering this code?

Essentially, the voltage of the High Voltage Battery was NOT being seen at the Inverter / Converter assembly.

The Inverter / Converter assembly is next in line after the High Voltage Battery. They’re joined by the 2 High Voltage cables only. Pretty straightforward stuff.

So why is the Inverter / Converter Assembly not seeing the same voltage as the High Voltage Battery?

Five main possible reasons:

• Faulty junction block assembly at the output end of the High Voltage Battery. This carries the contactors that close to supply the High Voltage to the Inverter / Converter Assembly.
• The High Voltage cables that join the High Voltage Battery to the Inverter / Converter Assembly.
• High Voltage Battery itself.
• Inverter / Converter Assembly.
• Low voltage connections / wires to HV Batt and / or Inverter-Converter.

Testing.

No.1: What voltage do we have at the High Voltage Battery? What voltage do we have at the Inverter / Converter Assembly.

Obvious and we needed to know this.

High Voltage Battery voltage was taken from live data on the scan tool.

Total voltage showing: 208.5V

Whilst in the scan tool, it made sense to see if the sum of individual module voltages equated to the total overall voltage. We had 7 modules measuring 26.1V and 1 measuring 25.87V. This equated to 208.5V. Happy days indeed.

Whilst also in Live Data, we could see what the Contactors were doing when trying to initiate ‘Ready’ mode. Both the Pre-charge and Positive Contactors closed momentarily before Opening again straight away.

Something not right. Inverter / Converter Assembly was obviously not receiving any voltage as Contactors were open, not allowing voltage past them.

This did however prove they were being commanded and therefore the command and control ground side of those two Contactors was fine.

What next?

We’ve seemingly two ‘ok’ contactors but car not happy enough to close the 3^rd contactor; Or, 3^rd contactor not able to close??

I decided to be the Hybrid Control Module myself and take control of the contactors. The module itself is under the glove box.

Powering the contactors one at a time, I would be able to hear the audible ‘clicks’ of the contactors closing. First one, ‘click’. Second one, ‘click’. Third one, silence. Boom!

We still weren’t totally home and dry….

We could still have a control problem, a wiring issue, a ground issue, plus more.

I took the easy option. Swapped out the contactor for the known good. Re-tested. Audible ‘Click’. Boom! This car had a failed / burnt contactor.

Contactor replaced. Fault code P3004 – High voltage power resource cleared down, vehicle achieved ‘Ready’ mode and started and drove.

Loved that diagnosis.

Toyota Prius P3004 – High Voltage Power Resource