Check Engine / Hybrid Battery Sensor Failure / Code: P0A9C

A loud fan from the rear seat is yet another sign of a battery failure. The car has probably thrown more codes now since the GF drove it.

Sounds like you already know your options. If only needed for one more year, I'd go the rebuilt battery option from a reliable, local source who will honor their warranty because they can/will fail too. I'd check with Luscious Garage | Hybrid Specialists there in the bay area for their recommendation.

GOOD LUCK!

 

If you were here in SoCal, I can probably fix that up for you for a low cost. If you're only looking for 1 year, it shouldn't be too hard to get a rebuilt to last a year. Beyond that would be the unknown.

 

Welcome to the site. I'm not one of the battery experts but I don't believe the issue is a faulty sensor.

I agree with fotomoto that the symptoms you describe point to a failing battery.

Since the battery only has to last a year a refurb Dorman purchased through an auto parts store may be a reasonable alternative to a brand new battery. Read and understand the warranty before the purchase to ensure you are covered.

Luscious Garage does have a good reputation so contact them since you are local.

 

I agree with both these statements.

The code does not mean that the sensor is broken, it more likely means the component the sensor monitors (or the wiring between the sensor and the ECU) is flakey, and the repair manual will give the work up to further diagnose where the problem is.

Given the other information you have given, it leans toward the HV battery failing.

Options are getting a minimal repair done by someone (trustworthy) like JC91006 above, to get you through. Getting a complete battery replacement from a repairer/rebuilder is getting to be a crapshoot (6 month - 3 years) there days, as the pool of usable old modules gets scarcer and scarcer. Also too many charlatans getting into battery repair. The best of breed repair is a complete new battery from Toyota, but given your personal circumstance may not make complete sense as you will not get the total benefit from going that route. You are in a precarious situation, unfortunately.

 

I have a 2007 Prius, approx 175,000 miles. Replaced hybrid battery approx 1 1/2 year ago with a new Toyota hybrid battery. 12 volt battery replaced 3 weeks ago. Yesterday had red triangle with ! And check engine light. After checking for codes first time no code. Checked oil, slightly low, added small amount of oil. 2nd time of checking code, it is P0A9C, hybrid battery temperature sensor circuit. No notice of power issue, car seems to be running well. Any ideas of what the issues is??

 

Welcome to Prius Chat .

There are temperature sensors along the battery, so one might have a loose wire or connection issue.

If you’re pulling the code, what device are you using to do so?

Can you see the temperature it is reading?

Good luck and keep us posted .

 

Check if there is fluid movement in the inverter coolant reservoir, open the cap while the car is in READY. No movement would mean pump failed

 

I have 2005 Prius and after rebuilding the hybrid pack i broke one wire from temperature sensor by the clip. took it out sorted with wire put it back but getting the same error code. P0A9E, any help would be highly appreciated since its hard to find the part.

 

OK, my 2 cents worth. First you have to buy the techstream program from Ebay. Next, you can see each individual cells voltages in the hybrid battery. There are 2 modules per cell. Once you determine which cells are bad (usually a volt or more lower) you have to disassemble the battery and remove the jumpers(copper plates) from both sides of the battery and test each individual module in that cell. Youtube has a few videos on this. Ebay has good used modules for cheap. I use a setup to charge and discharge each individual module 5 times. The turnigy charger I use discharges down to 6v, then charges up to delta peak(Capacity), or full, which is not the same. You are wanting to cycle discharge/charge until every module says capacity. This is usually done by the 5th discharge/charge cycle for most modules. I usually let the battery sit for at least 24 hours and re-check voltages, any deviation in voltage is suspect. My first rebuild has lasted for 5 years and is still going strong. Any naysayers are just trying to sell you something. This is not rocket science. The temp sensors you are referring to are on the bottom of the cells I think there are 4? Be careful when replacing modules, you may break the wire to the sensor! I hope this helps somebody!

 

Great post, thanks for sharing.

Just a note on terminology, there are six cells in a module and two modules in a block. In a Gen 2 battery, there are fourteen blocks or twenty-eight modules for a total of 168 cells.

it is important to use the correct terms so that you are clearly understood and misinformation and/or confusion is minimized. It can be confusing for noobies to get to grips with the information when incorrect terms are used.