Prius won’t accelerate.

Welcome to PriusChat!!

Do you have any OBD2 codes worth posting in this thread?

FYI : you're moderated until you've posted 5 times.

 

Posting the actual codes would be helpful.

It sounds like the AutoZone person has ad libbed the explanation and some detail got lost in translation.

Having the actual codes would be more useful that a million and one guesses, which helps nobody.

 

Wen my HV battery was really failing I could produce a clutch slipping like over revving was really bad sounding had to accelerate slowly but could go 60.

 

P0171 has the fortune cookie message "System Too Lean (Fuel Trim)" and has many areas where the trouble could be. They are in order of elimination::

• Air induction system
• Injector has blockage
• Mass air flow meter
• Engine coolant temperature sensor
• Fuel pressure
• Gas leakage in exhaust system
• Open or short in A/F sensor (bank 1 sensor 1) circuit
• A/F sensor (bank 1 sensor 1)
• A/F sensor heater (bank 1 sensor 1)
• EFI M relay (integration relay)
• PCV valve and hose - PCV hose connection
• ECM

There is nothing magical that this code points to as in it is not just a case of swapping in a part. You have to methodically test and rule out was it isn't until you find what it is.

C1241 relates to weird supply voltage reaching the skid control ECU. That's not always because of a 12 V battery problem; it can be anything in the wiring bringing the power to the ECU. But if the battery voltage hasn't been checked yet, a C1241 code makes a good excuse to check it. You should be able to find more about that code by searching for it.

The repair manual is a good place to find full detail of the troubleshooting sequence.

 

The skid control route sounds good because when it thinks there's no traction, it stops delivery of power to the front wheels, merely allowing the car to creep forward as you describe.
Other faults, like wheel speed sensors or torque sensors might contribute to that, but they might likely drop a code as well, but can be otherwise.

 

That is not what this code is saying. You're shooting the messenger. It's about the 12 V power supply arriving at the ECU that is flakey for one reason or another. What it takes now is for a person to use the information at hand and work out the reason for the flakey power.

 

Exactly.

I wasn't picking on why the ECU might be misbehaving, just that whatever it's cause, the symptom looked more like it could be coming from that end.

After all, might not bad power to the ECU cause it to misbehave like that?

So I would have started out checking that code and voltage 1st, before doing the fuel code and it's longer list of possibilities. Just my 2cts.

 

While that might seem like a long list of things, I would still diagnose and solve the P0171 first.

 

Hi Doc
If you spend a long time reading a lot of PriusChat you will possibly reach a few conclusions:
1. You can try to fix this yourself. This will take you a long time and significant effort. You will need Techstream - you can buy a bootleg copy on eBay. You will need to understand how Techstream works and how to load it into your laptop and hook it up to your car. You will have to determine for yourself your comfort with using bootleg software. Opinions differ. I’ll give you mine if you ask. You will need a good 12v bat. Mighty Max is cheap and easy to adapt. You will need a 12v bat charger. I can tell you cheap sources of both if you ask. You will possibly need a HV bat charger. Ditto on this. And you will need to be careful and confident working with lethal high voltage.
2. You can find a good, knowledgeable, highly experienced independent Prius shop. They will do all of the above for you. At a possibly reasonable cost.

Do not expect help from Autozone or other such places.
Do not expect a Toyota dealer to be willing or able to fix your car without spending far far more than it is worth.

3. You can sell your car in the current inflated market to someone who is able or thinks they can fix it cheaply and use it or flip it to someone unsuspecting.

If you can afford a new car lease or are very lucky and can find a good used car through a trusted friend you can move on without months of hard complicated work. Your Prius has reached the end of its useful life as a no trouble vehicle.

Others will have different opinions.

I’ll gladly reply to direct questions.

Good luck.

 

Not with any great likelihood. While the traction and stability control is handled on the same ECU that handles the electronically-controlled braking and ABS, the functions are segregated, with their own warning lights and their own trouble codes. While one thing the traction control can do when it activates is send a power reduction request to the HV control ECU, to assume that's what it's doing, because of an assumed phantom TRAC activation, because the ECB logic has logged a C1241, would be going at least two significant assumptions beyond what is known.

It would be different if there were some further sign TRAC had activated, or more reason to buy that the observed lack of power was because of a reduction request from the skid ECU. (Note this would mean, if the cause was low voltage triggering a phantom TRAC activation, that the ECU was so low-voltage-impaired as to think it was in a sustained TRAC activation for no reason, but at the same time so functional it could properly log a C1241 and freeze frame about the voltage, and send a well-formed reduce-power request to the HV control ECU.)

Of course I'd regard the C1241 as worth fixing, but that's likely most effectively done just by looking up what that code is telling you, and following those troubleshooting steps.

Meanwhile, if the ECM is saying there's an excessive lean-mixture condition for the engine, why, there's a strong contender for a recurring, sustained, low-power condition right there.

 

Here is the workup for DTC P0171 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/Repair%20Manual/04pruisr/05/2054m/cip0171.pdf

Here is the workup for DTC C1241 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/21avn/cic12414.pdf

Notice how the C1241 workup has "detailed codes" (aka subcodes), knowing such may help with the diagnostic process.