Rough/pulsing engine & Check Hybrid System

I've been working on this for about 6 months and out of ideas.
I have a 2010 Prius with around 170,000 miles. Near the end of 2025, the engine started running rough with a pulsing/surging sound and threw a check engine light. I had it scanned at O’Reilly and was told it was related to the EGR system, but I no longer have the exact codes (I can try to track them down if that’s important).

Over the next few weeks, I removed and cleaned the EGR valve and cooler, cleaned the intake manifold (there was oil pooled inside), and replaced the PCV valve. After putting everything back together, the car ran a bit better but still didn’t sound quite right. The check engine light did not come back at that time.

In January, I took it on about a 2 hour highway drive. By the end of the trip, the engine started making a pulsing/surging sound again. After letting the car sit for a couple of hours, I started it again and it ran extremely rough right when the engine kicked on. I got the red triangle warning and a "Check Hybrid System" warning, and the car basically died and would not accelerated. I shut it off, restarted it, and was able to limp it to a safe place to park and eventually get it towed home.

I took it to a local mechanic (not a Toyota dealer). After diagnosing it, he said the hybrid battery needed to be replaced and believed that would fix the rough running and may have actually been the original cause that threw the EGR related codes as the battery was likely failing at that time. He also inspected the cylinders with a camera and said he didn’t see signs of a head gasket issue.

Since a new OEM battery was quoted to my by my local Toyota dealer at ~$5,500, I decided to try recondition the battery myself. I cycled all the modules multiple times through discharge/charge cycles (up to about 20 cycles) with the goal of getting >5 aH consistently per module. From what I found, “healthy” modules should be >5 aH, but most of mine wouldn’t reach that. I aimed for at least ~4.5 aH per module because replacement modules on eBay weren't advertised to be any better, then balanced the pack and reassembled it based on each modules best performance (all data below).

After reinstalling the battery, the car seemed to run better at first on a 5 mile drive but I could still hear a pulsing/surging engine. The next day, within a 10th of a mile, I again got the “Check Hybrid System” warning along with a check engine light. I don’t have an OBD2 scanner and it’s difficult to get the car somewhere for another scan.

I’m trying to figure out whether this really is still a hybrid battery issue or if something else is causing the rough/pulsing engine. Does this sound like a battery problem, or should I be looking at something else, or even a head gasket despite what the mechanic said? Did I recondition the battery incorrectly or incompletely? Did I rebuild the battery packs incorrectly?

Bottomline, what should be my next step?

Below is a csv of all my data from the battery reconditioning as well as how I rebuilt the pack.

Code:

Module,Pre-reconditioning Voltage (oc),Discharge 1,Charge 1,Discharge 2,Charge 2,Discharge 3,Charge 3,Discharge 4,Charge 4,Discharge 5,Charge 5,Discharge 6,Charge 6,Discharge 7,Charge 7,Discharge 8,Charge 8,Discharge 9,Charge 9,Discharge 10,Charge 10,Discharge 11,Charge 11,Discharge 12,Charge 12,Discharge 13,Charge 13,Discharge 14,Charge 14,Discharge 15,Charge 15,Discharge 16,Charge 16,Discharge 17,Charge 17,Discharge 18,Charge 18,Discharge 19,Charge 19,Discharge 20,Charge 20
1,7.95,3295,5042,3286,6500,3572,6500,4334,6500,4260,6500,4505,7000,4766,7000,4742,6500,4885,6500,3932,6500,4841,6500,4911,6500,5191,6500,4894,6501,5112,6500,4884,6172,4780,6500,5033,6500,5090,6500,,
2,7.96,3547,6500,3826,6500,4048,6500,4152,6500,4090,6500,4547,6500,3495,4982,4140,6500,4599,6501,2595,6501,4460,6500,4514,6500,4742,6500,4580,6500,4533,6500,4606,5450,4391,6500,4488,6500,4836,6500,4686,6500
3,7.95,1422,5578,2671,6440,3139,6478,3565,5611,3775,5926,3841,6500,3308,7000,4516,7000,3453,6500,4896,6500,4520,6500,4981,6500,5012,6500,4636,6500,5081,6501,4873,6500,4765,6500,4791,6500,4958,6500,4882,6501
4,7.97,1933,6010,2935,6500,3396,6500,3629,6500,3497,6500,3898,6500,3386,7000,4471,7000,4481,7000,4442,7000,4437,7000,4234,7000,4905,7000,4736,6500,4925,6500,5069,6500,4146,6500,2444,6500,4913,6501,4980,5396
5,7.95,1821,4360,2844,4460,3101,6500,3960,6096,4181,6500,4233,6500,3743,7000,4568,7000,3836,6166,4790,6500,4708,4544,4017,6501,4741,6500,4773,6501,5027,6500,4896,6500,5125,6500,,,4874,6500,4812,6500
6,7.94,1222,5614,2645,6500,3188,5708,3373,5355,3540,6500,3816,6500,3396,7000,3923,7000,3792,7000,4213,7000,4556,7000,3834,6501,5092,3606,3175,6501,4894,6500,4830,5745,4660,6500,5222,6500,4867,6500,5113,6501
7,7.94,1411,5220,2772,6248,3312,4950,3466,5487,3796,6500,3866,6500,4690,6500,4793,6500,4878,6500,4745,5588,4597,6500,4971,6500,4643,6500,4771,6501,4867,6501,1748,6500,4896,6500,5125,6500,4874,6500,4812,6500
8,7.94,2379,5139,2748,5551,2904,5457,3060,5711,3208,5734,3228,5968,3222,6089,3541,6152,3651,6423,4258,6310,3212,7000,4437,7000,4457,7000,3945,6500,4639,6500,4774,5961,4858,6500,4894,6501,4919,6501,5127,6500
9,7.97,2374,5653,3277,5816,3632,6370,3993,6500,3935,6500,4295,6500,3531,7000,4369,7000,4603,7000,4070,6501,4924,6500,4881,6500,4763,6501,4782,6500,4966,6500,4908,6500,4911,6500,4989,6500,4993,6500,4763,6501
10,7.96,3201,6500,4219,6500,4156,6500,4186,6500,4692,6500,4349,6500,3698,7000,4745,7000,4621,7000,4841,6500,4825,6500,4535,6500,4633,6500,4708,6500,4908,6501,4710,6500,4907,6500,4732,6500,4693,6500,4905,6501
11,7.94,1547,4794,2370,5183,2809,5508,3155,6107,3475,6215,3695,6500,3231,6500,4164,6500,4313,7000,4191,7000,4423,7000,4441,7000,4681,6500,3934,6214,4926,6500,4709,6500,5058,6501,4872,6500,4739,6500,4738,6500
12,7.94,1278,4541,2589,5550,3170,6090,3545,6500,3570,6500,3874,6500,3288,6500,4136,7000,4110,7000,4266,7000,4235,7000,4258,7000,4665,7000,4896,6500,5013,6500,4311,6398,4979,6500,5134,6500,5128,6500,,
13,7.95,1331,5074,2766,6217,3376,6500,3912,6500,3946,6500,3966,6500,3828,6930,4848,7000,4833,7000,3674,6500,4680,6501,4646,6500,4898,6501,4719,6500,4688,6501,4812,6500,4687,6500,4737,6501,4822,6500,4759,6501
14,7.98,3168,6500,4298,6500,4332,6500,4436,6500,4611,6500,4631,6500,3521,6500,4762,6501,4612,6500,4905,6500,4669,6500,4603,6501,4901,6500,4940,6500,4645,6500,4630,6501,4450,6500,4486,6500,5034,5512,4484,6500
15,7.94,2474,6083,3405,6500,3843,6500,4954,6500,4986,6500,5545,7000,3890,6500,5021,6313,5123,6500,,,,,,,,,,,,,,,,,,,,,,
16,7.94,2246,4482,2986,5482,3482,6196,3964,6500,4486,6500,4250,6500,3595,7000,4792,7000,4123,6500,4864,5979,4917,6026,4734,6500,4892,6500,5117,6501,5019,6500,,,,,,,,,,
17,7.97,3384,6500,4495,6500,4456,6500,4489,6500,4449,6500,4817,6500,3827,6500,4676,6500,4796,6501,5091,6501,4872,5929,4839,6500,4778,6501,4785,6500,5063,6500,5122,6500,,,,,,,,
18,7.95,1292,4464,2526,5512,2866,5868,3279,5318,3510,6370,3601,6500,3128,6383,4144,6199,4270,6433,4277,6500,4576,7000,3535,6396,4857,6500,5036,5916,4776,6500,4890,6501,5157,6500,5194,6500,,,,
19,7.96,1868,5829,3190,6500,3640,5467,3884,5881,4058,6081,4143,6500,3077,7000,4102,7000,4140,6894,4502,7000,4626,7000,4536,6500,4525,6500,4630,6500,4431,6500,4556,6500,4709,6500,5007,6500,4711,6276,4932,6500
20,7.94,1242,5666,2920,4839,3301,4844,3507,6500,3597,6500,3882,6500,3383,6500,4263,6485,4299,6901,4141,7000,4281,7000,4299,7000,5199,7000,4148,5897,5037,6256,4976,6500,5008,6501,5182,6501,,,,
21,7.97,2024,4560,3178,4842,3493,6500,3968,6500,4281,6500,4312,6500,3617,7000,4622,7000,3591,6501,4686,6500,5076,6495,5038,6500,,,,,,,,,,,,,,,,
22,7.94,2109,5510,2742,5698,3185,6413,3692,6500,4019,6175,3953,6500,4031,6500,4627,7000,4533,7000,4624,7500,3999,5789,4810,6501,5146,5028,4328,6500,5217,6500,4918,6500,4959,6500,5092,6500,4924,5905,4945,6501
23,7.96,2434,5936,2970,6500,3257,6500,3251,6342,3720,6500,3900,6500,3133,7000,4392,7000,4365,7000,4701,7000,3669,4959,4175,6500,4855,6501,4837,6501,4689,6500,4870,6501,4986,6500,4986,6500,4888,6205,4901,6500
24,7.97,2272,4655,3131,5334,3470,5818,3759,6442,3740,6500,4159,6500,3538,7000,4175,7000,4616,7000,3716,6501,4869,6500,4551,6278,4814,6501,4965,6501,4594,6500,5012,6500,4831,6500,4690,6500,4700,6500,4853,6500
25,7.96,2204,6500,3031,5407,3587,5525,3826,6500,3991,6500,4273,6500,3623,7000,4746,7000,3903,4860,4108,6500,4843,6500,4958,6500,4776,6500,4988,6500,4761,6500,5086,6500,5239,6500,,,,,,
26,7.97,1653,4021,2628,6331,3177,6256,3599,6500,3809,6500,3922,6500,3341,7000,4207,7000,4770,7000,3695,6500,4872,6500,4817,6500,4743,6500,5020,6500,4882,6500,4830,6500,4658,6501,4789,6500,4744,6500,4724,6500
27,7.96,3741,6500,4247,6500,4352,6500,4486,6500,4490,6500,4541,6500,3599,6500,4635,6500,4589,6500,4626,6501,4711,6500,4620,6500,4590,6500,4782,6500,4609,6501,4896,6500,4576,6500,4925,6500,4925,6501,4601,6500
28,7.94,2326,5182,3369,6500,3869,6500,4065,6500,4171,6500,4385,6500,3991,7000,4326,7000,4549,7000,3649,6500,4311,6500,4365,6500,4931,6500,4573,6500,4758,6500,4652,6500,4583,6501,4809,6500,4690,6500,4678,6500

Below is how I rebuilt the battery packs:

Code:

Pack,Module,Max mAh
1,15,5545
1,25,5239
2,6,5222
2,22,5217
3,20,5199
3,18,5194
4,1,5191
4,12,5134
5,8,5127
5,5,5125
6,7,5125
6,17,5122
7,16,5117
7,3,5081
8,21,5076
8,4,5069
9,11,5058
9,14,5034
10,26,5020
10,24,5012
11,19,5007
11,9,4993
12,23,4986
12,28,4931
13,27,4925
13,10,4908
14,13,4898
14,2,4836

I know this is long and a lot, so thanks so much for reading this, and thank you if you're able to provide some help!!

 

Thank you all for the help! I looked at the Autel website and don't see either a "autel maxi 200 code reader" or a "Autel AP200". The closest scan tool I see is the Autel MaxiScan MS300 (I'm restricted from posting a link to it in their website). This doesn't seem right though. I just want to make sure I'm buying the right tool for this.

Once confirmed, I'll get the scanner ordered! I do live in a rural area and mail takes a week. So my response with the codes may be delayed. But I'll be back! Thanks again!

 

I was able to drive the car to O'Reilly's to get a scan. I figured I'd start here since their scan is $60 cheaper. On my way to O'Reilly's, my dash had an orange triangle, Check Hybrid System, and check engine lights on. On my drive home, I just had the check engine light on.

Here is was the scan found:

Powertrain Diagnostic Trouble Codes
P3190 - Code P3190 indicates that with the engine running at a stable speed for a predetermined period of time, actual engine torque in relation to expected engine torque was below acceptable limits.
Primary DTC - Poor Engine Power
Most Likely Solution - Replace Evaporative Emissions (EVAP) Vacuum Switching Valve (VSV) and Reprogram Engine Control Module (ECM)
Suggested Parts - 1
Canister Purge Valve/Solenoid - The canister purge valve and purge valve solenoid are part of the evaporative emissions (EVAP) system that recirculates emissions to increase gas mileage and performance. Usually controlled by the engine control module, canister purge solenoids collect harmful vapors, and after combustion, release stored gases into the combustion system once the engine has reached operating temperature.

Additional Powertrain Diagnostic Trouble Codes
P3190 - Poor Engine Power - Stored
P3190 - Poor Engine Power - Permanent

The O'Reilly worker said he didn't think the suggested fix was right and, based on mileage, suggested replacing the fuel pump and fuel pump seal.

Hopefully this is enough information. If not, I can look into buying the Autel tool. Thanks!

 

I have the Autel on order. Please give me several days to respond back with scan results as shipping is slow to where I live. Thanks!

 

While I wait for the Autel tool to arrive in the mail, I did the test in the video you provided, rjparker. I went into the kitchen and found my wife's favorite metal spatula to use to block the path from the EGR valve to the intake. I drove the car around the block a couple times and the motor didn't pulse or surge. I took the spatula out and carefully put it back in the kitchen drawer, then did another test drive. I made it to the end of the driveway and the motor started doing the pulsing/surging. I did an EGR system cleaning at the start of this 6 months ago, but I certainly may have not done a good enough cleaning on the system. Sounds like I need to put in a new valve and manifold based on the video. Should I move forward with that or continue to wait for the Autel scanner to arrive? Thanks again for the help so far!

 

Thanks rjparker. I'll get the valve kit ordered!

Do you think the Autel scanner is needed still?

Is the TSB refered to in the video T-SB-0027-16? I want to make sure I have the right computer software update for when I go talk to the dealer about getting it after I change the valve. If that's right, the software update looks like it's ECU part number, 89660-47306. Thanks!