03 prius 236k shuddering problem

Here are my suggestions:

1. Get Mini VCI so that you can retrieve the DTC logged by your car.
2. Once you have the DTC then it will be possible to determine whether the inverter or transaxle need to be replaced.
3. Consult techinfo.toyota.com for factory repair manual info. This will help you assess whether you can do the work yourself.
4. After you have identified the failing part, buy a used part on eBay or a local salvage yard, and install it or have it installed by an independent who is trained on Toyota hybrids. If there is no such individual in your geographic area, see if your local Toyota dealer will install used parts. If they won't then you'll have to DIY or get rid of the car.

 

Ok, let's go over some basics:

• Does the engine run while it is in "P" and shudder at the time? - This determines if the traction battery, engine, MG1, and half of the power inverter are working.
• With the engine running, does the coolant fluid in the resevoir next to the inverter show two levels and turbulent? - This checks the inverter coolant pump and channels are working. This is a known weakness in our NHW11 Prius.
• With the car in "P" and holding the brake hard, floor the accelerator, without moving does it shudder? - This brings in part of MG2 and the other half of the inverter. Look to see if the engine revs and the energy arrows show the traction battery charging. We want to eliminate any running gear.
• What is the level of the traction battery charge? - This is the battery that starts the engine so we want to avoid getting a second problem.

You are going to need a Prius-aware scanner:

• miniVCI (from Horse) and Windows XP - this scanner is out-of-the-box able to communicate with the half-dozen Prius control computers that have the error codes and metrics to tell us what is going on. This is your primary diagnostic tool.
• (ALTERNATE) Scangauge II - requires Xgauge entries, up to 30, to communicate with the control computers. Generally, capable of eventually getting the same miniVCI data, entering an XGAUGE is as easy as sending a text message on a cell phone.
• (ALTERNATE) Android and OBD scanners - I don't have experience but those I trust those reporting it has Scangauge II capability.
• others like the Graham scanner (no longer in production) and AutoEnginuity (~$500).

You will also need the shop manual:

• Volume I and II - available via eBay, used, I like paper manuals
• (ALTERNATIVE) Toyota Technical Information Service - rented per day, download the specific sections of interest

Since you have a trailer that can carry the Prius, can we assume you have a metric wrench and socket set?

Does your wife have alternate transportation? There is a difference between 'like' and 'need' but Saturday is important too.

Bob Wilson

 

This is good:

It means MG1 and that part of the inverter are working.

I assume these are from the Toyota diagnosis sheet:

MG2 stator shorts are the primary transaxle failure mode. For a good introduction:
Replacing Our Second First Generation Prius Transaxle

With a Prius-aware scanner, you can monitor engine (ICE), MG1, and MG2 temperatures. A shorted, MG2 stator winding works like a shorted generator and generates a lot of heat. Normally the temperatures, ICE > MG1 > MG2 but when MG2 has a short, any motion leads to MG2 rapidly heating and temperatures well in excess of 100C. So here is the last test without a Prius-aware scanner.

Get the car up to 20-30 mph and shift into "N" which turns off all inverter power flow. If the car continues to shudder in "N" while coasting, the MG2 stator has a short and it will have to be replaced. The inverter could still have a problem but MG2 is toast.

Assuming the coasting in "N" test shows it shuddering, it is time to inspect the transaxle oil. Prepare a clean, dry water/soda bottle to hold an oil sample. Drain the oil and take a sample and drop the pan and inspect for debris. Let us know if it smells burnt.

Then comes a decision point: (1) swap with used, or (2) replace MG2 stator. There are advantages and disadvantages to each approach which we can discuss after this last test.

Bob Wilson