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2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

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  #1  
Old 06-14-2018, 05:39 PM
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Default 2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

A newbie here trying to consolidate information from many other threads in an effort to determine how to proceed. I have a 2005 Honda Accord Hybrid with 172,000 miles. I hit a deer and luckily the car was not totaled. It had $3300 worth of damage ($500 deductible) to the front end, which was fixed through insurance. After it was fixed, I drove it 7 miles home and a few days later drove it 7 miles to a garage to get the 2 front tires replaced (and an alignment, another $360) so that it would pass inspection.

After the tires were replaced, which included a couple of engine starts, I took it across the street it to get an inspection sticker. It was at that point that I noticed the IMA light was on (I don't think it was on before that). The codes P0A7F and P0AC4 were produced during the inspection. Then, while driving home, the Check Engine (MIL) light came on! Everything continued to run fine but the dash sometimes indicated recharging when I was accelerating, which seemed strange. I didn’t notice if the Battery Level Indicator was going up or down.

Before I conclude that I need a new battery pack, I’d like to make sure that there aren’t other solutions to the codes/problem. First of all, the car sat at the body shop for 3 or 4 weeks before they could get to it. Reading this forum, I now know that’s not good. Could sitting unused for that amount of time have caused these particular codes to appear?

Also, when I purchased the car used with about 95K miles on it (with the original HV battery, I assume), I think I remember reading that mechanics have to be careful when handling this car because of the hybrid connections/technology. Is that really true, and, if so, is it possible that something they did while fixing the body damage in the front end could have caused these codes?

Next, my 12V battery is about 5 years old. I’ve read here that some people have solved the problems with these codes by replacing the 12V battery. I’m suspicious that that may not have really solved the problem, though, since replacing the battery means it was unhooked and that could have cleared the codes. Maybe the codes were just cleared temporarily and the owners never came back to this forum to update their experience (although everyone here seems to be very conscientious).

I have a scan gauge, (which shows the codes P0A7F and P0000, btw) so I’m able to clear the codes. It doesn’t have the latest firmware – it’s on Version 3.17mb. I’ll pay for the upgrade soon.

Please let me know if there is something in the list below that I should definitely NOT do. For example, could any additional harm at all occur (to the HV battery or anything else) if I drive the car with the Check Engine light on during any of these steps? According to S Keith, driving on an imbalanced battery can immediately ruin it. I’ve already driven it 20 miles or so since the body shop. Letting is sit unused is bad and driving on an imbalanced battery is bad – you can hopefully understand my confusion.

What I’m wondering is, should I clear the codes and drive the car or try something else first? I’m hoping someone can provide the order in which I should try various remedies. I’ve read some of the threads that may apply and the following is my first cut at a comprehensive list.

Step 1: Clear the codes. Drive as usual to see if the DTC codes come back.

…or Step 1a: Clear the codes. Drive the prescribed method on pages 268 & 269 of the Owner’s Manual to reset the ‘readiness codes’ and see if the DTC codes come back.

Step 2: Disconnect the 12V battery (for how long?) and then reconnect it. Drive as usual to see if the codes come back.

…or Step 2a: Triple 12V reset and charge with car (from an S Keith HCH thread). Drive as usual to see if the codes come back.

…or Step 2b: Disconnect the 12V battery and perform a load test to determine if the battery is good. If good, put it back in. If not, buy a new 12V battery. Drive as usual to see if the codes come back.

…or Step 2c: Anything else I should do with the 12V battery?

Step 3: Determine if I need a software update (how?). Then start all over at Step 1? Where does this fit in the process?

Step 4: Check the 10 voltages S Keith mentions on the orange plug that connects the battery to the BCM. (“check those voltage taps before taking it to the shop. If there is more than 0.2V discrepancy between the highest and the lowest, the pack is going to fail sooner rather than later”) Is there a thread that describes/shows the pairs and how to do this for a 2005 Accord Hybrid?

Step 5: Try to rebalance the HV battery with a diagnostic scan tool or with a grid charger. (I’d like to keep the car for another 3-5 years so if this is only good for 1-12 months I’d be inclined to skip it. Unless that is for a one time rebalance and using the Prolong® Battery Charger (with or without the Discharger) multiple times can keep me going for 3-5 years.)

...or Step 5a: Buy a Bumblebee replacement battery.

Sorry for all of the questions but I’m hoping this will also help others in the future if they see things all in one thread. Any rearrangements, corrections, additions or subtractions (or simplifications!) are very welcome.

Thanks very much for your help!!!
 

Last edited by kober123; 06-14-2018 at 05:42 PM.
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  #2  
Old 06-14-2018, 10:43 PM
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Default Re: 2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

I suspect your battery has failed or is grossly imbalanced due to it sitting during the repair.

Intended order of operations:

0: LOAD TEST 12V to confirm it's good. Voltage check does not suffice.
0a: check your main ground cable for corrosion. There are likely others you'll have to look for.
1: Worth a try
1a: Normal driving with 2-3 starts will usually set DTC ready, but no harm in driving the prescribed cycle
2: 60 seconds
2a: Worth a try
2b: moved to 0
2c: moved to 0a
3: 99.99999% unlikely
4: Will be a similar plug and follow a similar pattern.
5: not possible with a "diagnostic scan tool". Grid charger worth a try, but expensive if it doesn't work. Tap voltages after sitting for 24 hours will give a clue.
5a: always an option.

IIRC, P0AC4 is basically "I have an IMA problem" and the P0A7F is "yeah, it's the battery"
 
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  #3  
Old 06-16-2018, 09:42 AM
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Default Re: 2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

S Keith, Thanks very much!! This is exactly what I was hoping for!

You’re right about the codes… AutoCode said “The P0AC4 code is an information code only, if there are no other engine codes, then the Hybrid Powertrain Control Module needs to be diagnosed.The P0AC4 code indicates the Hybrid Powertrain Control Module has set an emission related hybrid powetrain code.”The mention of the powertrain sounded very expensive.The title in AutoCode for P0A7F was “Hybrid Battery Pack Deterioration”.Also expensive sounding.That’s what made me search for potentially less expensive solutions.

I’ll work on the 12V battery and the ground cable first. When you say “There are likely others you'll have to look for” do you mean other cables related to the 12V battery?
 

Last edited by kober123; 06-16-2018 at 09:45 AM.
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  #4  
Old 06-16-2018, 06:25 PM
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Default Re: 2005 Honda Accord Hybrid with P0A7F and P0AC4 codes

There will be other grounding straps from the engine and/or tranny to the body and/or engine mounts.
 
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