Visiting a 2001 Prius

I visited the owner of a 2001 Prius with 250k miles and a few maladies. The first visit was finding the location and diagnosis. We talked and later I sent follow-up e-mails. But I wanted to bounce my findings off the community. One thing that warmed my heart was the owner had the 2001 shop manuals and electrical diagram book. I brought my Graham mini-scanner to read and reset the codes.

ENGINE

The owner reports 'it uses oil' and it had been 'de-carbonized.' Inspection of the throttle body indicated it needed cleaning but it wasn't sticky. The owner reported one starting event last summer.

The engine started and warmed up normally. We cleared the codes and took it for a test drive with the steering ECU enabled.

CATALYTIC CONVERTER

The owner reported "reduced efficiency" from an earlier code. Monitoring the O{2} sensors showed both reporting pretty much the same values. I explained that burning or using oil is death to catalytic converters. Repairing the catalytic converter and/or O{2} sensors makes no sense until the root cause, engine oil consumption is fixed first.

STEERING TORQUE SENSORS

The steering sensor 'jitters' had occurred. So the owner has the steering ECU power routed through a switch between the light adjustment and outside mirror adjustment control. By powering off the ECU, the car is more stable as there had been an event at high-speed. The user reports having seen the steering rock on its own. Normal operation is in manual mode with the PS light.

During the test drive, the steering behaved normally. However, we discussed the possibility of using a pair of pi filters to take out the electrical noise. Later examination of the manual shows a 0.5-4.5 VDC range, which means electrolytic caps and chokes should work. But testing the steering fix safely needs to be planned ... perhaps reducing motor power with a load resistor.

TRACTION BATTERY

The battery ECU showed P3011, bank 1 weak. During the test drive and monitoring, there was a 0.20 V difference but bank 1 was always listed as the low pair. The owner reported a recent cross country trip was interrupted with the fan running and visiting a dealer who reported the battery needed replacement. Obviously bank 1 is marginal. The car had the terminal sealant applied at the dealer.

I left a pair of used modules for experimentation, the owner installs PHVC systems and solar systems. We discussed options of removal, inspection and test; replacement of two weak modules with refurbished; rebuild using NHW20 modules; replacement with salvage battery; and contacting "Re-InVolt."

I also explained that error codes and indications can be cleared by disconnecting the 12 VDC battery. I also sent a note about jumpering the OBD to cause the codes to flash out.

OPERATION

I shared that cruising at 65 mph returns excellent highway mileage and when climbing hills, 55 mph puts a minimum stress on the traction battery. I suggested using semi-trailer trucks as a pacing vehicle as the ones that cruise at 65 seem to have a Prius friendly driving profile since they also need to save fuel.

RECOMMENDATIONS

The traction battery is most at risk. This may be a case of one or two weak modules. The low cost solution is to remove and inspect the battery with a spare pair ready. Check and clean the buss bars and re-install the battery. The two removed modules can be tested offline for capacity as a measure of pack health.

Inspection: two people, 8 hours, $50 modules
Rebuild: two people, 8 hours, $500-1,500 modules
​

Rebuilding the engine, either a top-end or whole build, is the next priority. Although oil burning engines can run for hundreds of miles but the risk is eventually a combination of high temperatures and low oil can lead to an engine failure. The spark plugs can also coke-up and need cleaning or replacement. However, there is no evidence of other mechanical issues. This can be deferred but there are two versions of rebuild, cylinder head only, or bottom end too.

Valves: one person, 8 hours, 3-4 days for shop, $400 est.
Bottom: one person, 24 hours, 7 days including shop, $600 est.
Swap salvage: one person, 16 hours, no shop (thanks Patrick), $800 est.
​

Steering ECU has an acceptable workaround: a power switch on the ECU. When power assist is needed, it can be turned on. I would like to try a pair of pi filters but that isn't my car. Testing remains a risky venture suggesting depower or reduced power to steering assist motor until confidence in system returns. I do have a failed steering assembly that I need to run forensics on.

pi filter: one person, 2-4 hours, $20 or less
steering replacement: one person, 8 hours, $1,000
​

Catalytic converter does not need to be touched until the engine oil consumption is fixed. The O{2} sensors appeared to work but if they fail due to carbon coke-up, fuel efficiency will drop dramatically.

O{2} sensors, one person 2-4 hours, $50
catalytic converter, one person 4 hours, $200, muffler shop, $250
​

There is no record of transaxle oil or inverter coolant change. I'd recommended doing a combined, engine oil, inverter coolant and transaxle oil change:

engine oil: one person, 1 hour, $25, filter and 4 quarts
transaxle oil: one person, 1 hour, $25, gasket and 5 quarts, Type T-IV or Type WS
coolant: one person, 1 hour, $25, pvc hose to bleed air
​

This raises the question of when should a non-crash vehicle be retired? Should this troubled car be sold, eventually winding up in auction? Personally, I see this car as Do-It-Yourself servicable. They have spare vehicles, a shop and skills to keep it running. I'm also willing to come back, they are about an hour away, and 'turn a wrench' ... its a Southern' Thang you might not understand.

Some of the 'patch' fixes make sense by opening the shopping window for replacement parts on Ebay. The rule of thumb is: Good, Fast, or Cheap, pick two. By expanding the window to shop for parts, better quality can be gotten for a relatively low price.

Thoughts?

Bob Wilson

 

We have enough Prius already but I don't mind 'turning a wrench. <grins>

Bob Wilson

 

I wonder if the salvage engine, possibly engine and transaxle, are bought at one time, does it make sense to do the heads and bottom overhaul before installation?

My thinking is we only have the salvage yard's report of the vehicle state and no idea of what the original owner had been doing. With the engine out, it is a lot easier to do the head, bearings, and rings. In effect, installing a rebuilt engine, not just a salvage.

If the engine and transaxle are bought as a unit, then any future transaxle replacement can be handled using the spare. Alternatively, put all parts back for sale on Ebay to recoup part of the purchase price (and clean out the shop.)

Now I noticed they also had a slightly rusting VW MicroBus body and with a little sheet metal work ... hybrid MicroBus. <GRINS> ... Better be careful, I could spend all summer there.

Bob Wilson

 

<AHEM>

250,000 miles / 10 years ~= 25,000 miles / year

If we can develop a battery that runs on air and gasoline or diesel, I think we have a winner. <wink>

Bob Wilson

 

Hummm, I have this idea ... swap steerings. I don't have a failed steering assembly and the skills to deal with it. He has a failed steering assembly but doing 25k miles/year, may not have the time to fiddle with it. ... Hummmm.

Bob Wilson

 

The Graham Miniscanner doesn't have that capability. If you get a chance, Google it up. For the price, it is a handy unit but not as fully featured as the Toyota or Autoengiuity (sp?) units.

Bob Wilson

 

It is one of the best features of the Graham miniscanner. This means we don't have to clear the codes by disconnecting the 12 VDC battery and also lose the fuel trim data. It really is a dandy part:

The Prius Mini-Scanner Project

As NHW11s come out of service, I have a standing offer to buy any Graham mini scanners so I can rent them to others who need a scanner. Just another contribution to the community.

So are you planning to build and sell a "freeze frame data" display device?


Bob Wilson

 

We did this to determine if it is an intermittent or hard failure. It was interesting that during the test drive we didn't see the codes come back. Regardless, we were able to verify:

• O{2} sensors showing the same values - reduced catalytic converter
• Module pair #1 consistently showing the lowest voltage - the P3011 code cause
• Steering jitter did not return but we know it is intermittent - he has a workaround that powers off the steering ECU

Bob Wilson