Low MPG, Low Acceleration, Battery down to one bar when highway driving, Catalytic Converter?

Put in diagnostic mode so engine stays on then have somebody hold the gas down then pour seafoam throttle body if a drives better clould be catalytic converter was just dirty

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check the oil level, battery voltage and air cleaner for leakage.

 

Also check plugs n boots

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Well if you have over 100k miles, I would recommend having the spark plugs and boots changed. Also would check out all the stuff Bisco is talking about as well.

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That sounds like a fairly severe mechanical knock to me. How many miles on the engine? What is the oil level now, and do you normally check it between oil changes?

Your hybrid battery is probably getting weaker, and when it drains to a low charge the engine has to work harder. I assume you've had no alerts about the hybrid system, just the check engine light?

A clogged cat could cause rattling and knocking, so that's probably it. But you need to consider the cause of the cat getting clogged--excessive oil consumption or very poor fuel performance, thus the need to check plugs and coils (the "boots" referred to above) and fuel injectors, as well.

Before spending big money on a new cat, also consider the hybrid battery health and another possible major cash outlay.

 

Two signs of the hybrid battery getting weaker are rapid changes in the state of charge indicator bars, and the cooling vent fan running often (grille on the right side of the back seat.

If that were an exhaust leak, it would be up front before the muffler, and you'd probably hear it under more conditions. And it wouldn't cause low acceleration.

Oil level sounds good now, but do you check it regularly, and have you checked it before your oil change? The oil quantity between the dots is about 1.6 quarts.

 

Get in the habit of checking your oil every 1500 - 2000 mi. But not only that, get in the habit of topping it up if it is any lower than what you have, add about 5 fl oz at a time then check. You will get good at estimating how much you need real quick. Do NOT over fill. If in doubt a little under (1/10) is better than 2/10 over.

Think again!

How did you get going again after running the HV battery flat? If it didn't need to be charged externally, you're probably ok. But an Out Of Gas situation in a Gen II will allow the HV Battery to go right down to 0% SOC, from which you cannot get going again without a tow to Toyota for the HV battery to be charged.

 

If you go to the dealer with this problem, expect a $100+ diagnostic fee (which may be applied to repair work), and a battery replacement cost estimate in excess of $3500. Your catalytic converter also probably need to be replaced, and the dealer will probably want well over $1000 for that.

The market value for this car, the way it drives now, is probably about $1000, and that's what the dealer may offer for trade in.

If you don't have work done, you'll owe them at least $100 for the diagnostic.

Sorry for the bad news, but you asked....

 

That might work out. You can research your battery repair/replace options here, and budget accordingly. Some folks repair them for under $100 and a lot of labor, some will take a chance on a $1000 rebuild with a limited warranty, some will invest $400 in a grid charging system. All those options entail more risk for the cost savings.

Aftermarket cats can be gotten for a lower price, around $250 I hear, if you can find someone to install it, maybe around $100 shop time. That will depend on your local emissions testing and inspection program, too.

Remember we don't really know why the cat failed. A common cause could be excessive oil consumption, another is unburned fuel. Or there's physical damage and a replacement will take care of it.

 

And please, don't make a major decision based on solely my input. I'm just a guy on the internet. Hopefully others will chime in with their suggestions.

 

If you were able to get going after a jump, then your HV battery did not run down under 40% SoC. This is represented by the lowest (purple) bar. If you went lower than that you would have needed an external charge to get it back up to at least 40% to get the car started. The fact you did not need an external charge on the HV battery means it did not happen, so this event is probably unrelated. What it does point to is problems with the auxiliary 12 V battery.

This does point to problems with the HV battery.

If you take it to Toyota, there is only one course of action that they can take. If there are HV battery related codes, they will replace the battery. If there are no HV battery related codes, they will do nothing. The cost for placing the HV battery varies, so it pays to shop around. The cheapest I've seen reported on here for a Toyota shop on here (excluding goodwill contributions from Toyota HQ) are ~$2800 up to a worse case scenario of ~$4500.

Going back to the loud knocking noise on acceleration, aside from replacing the battery, your engine may be shot. This could be due tot a low engine oil event sometime in the past or it could be from all the extra work the ICE is now doing to compensate for the bad HV battery.

In any case you need to seriously weigh up what you might spend vs cutting your losses and moving on. 185,000 miles is a good run.

 

If the code you got was a P0420, then that does not necessarily mean "the cat is shot". It means the cat efficiency is impaired. There can be many causes of impaired cat efficiency.

Would just like to remind you of andrewclaus advice.