Looking to buy a Gen1 Prius with Steering, oil consumption, and P0420 code

Have a gen2 and gen3 Prius and a Tesla Model S for 100% electric Fixing cars is a hobby and looking at a gen1 Prius with 209k miles on it. Listed for $1000 probably can get it closer to $500 due to $3500 shop repair quote received by the previous owner for the steering rack replacement.

Runs descent but have the following issues. Thought I consult the experts before proceeding.

Steering Rack

Has code C1521 and C1522 (motor issues). Not the typical C1513 related to the torque sensors. Steering is not very linear. Centered steering wheel has little/no response until wheel is turned just a bit given a sluggish steering experience. Turning left is harder than right. There was no wheel shake during my test drive. Previous own also mentioned no steering wheel shakes.

Read about the column nut recall (this car had it done in 2012) and learned all about the torque sensors by reading quite a few posts+links. In particular, ChapmanF's signal traces on bad+good sensors in this thread

steering gear jitters | PriusChat
Gen 1 Prius Steering Rack Failure, Code C1513 Torque Sensor Malfunction - Luscious Garage | Hybrid Specialists

I've dealt with potentiometer rotation sensor wear before on cars (fixed Volvo pot based throttle body by switching to hall effect contactless sensors).

I also read the following post on multiple trips to the dealer on the nut recall job where steering didn't feel right afterwards (hard turning left, hard turning right etc etc) Seems like this particular service department didn't know what they were doing. But obviously there are some kind of adjustments that must be done correctly to get the steering to feel right. Anyone know what was the problem encountered in this thread? Sounds like 1 of the 2 problems I have with this steering : More muscle to turn left.

My steering WAS fine. Then Toyota worked on the recall. - Toyota Prius Forum : Prius Online Toyota Forums

Anyone has an idea what might be causing the lack of immediate response on near centered steering wheel? Perhaps the intermediate shaft fitting has play? (saw an youtube video on a gen2 where the fitting was stripped)

Anyhow, I suppose I can be the pygmy pig if I buy this car for cheap and try the following

- See if the intermediate shaft fitting is clamped on tight
- See what the 2 steering motor codes are about
- cleaning the torque sensors to see improves things if nothing else pans out

If anyone has thoughts on this, love to hear.

Engine oil usage

Current owner shows 1/2 quart usage / 500-700 miles. I can see wet oil pan towards the rear of the car so there might be a leak towards the cabin side of the engine. Looks like oil doesn't drip on the ground.

Perhaps the PCV check valve might be clogged?

My question is does gen1 have any kind of common oil leak or oil consumption problem? Again car is at 209k miles.

P0420 code (cat efficiency)

Dealt with this on another car recently. Either replace cat or a spacer on the rear O2 sensor to pull it out of the post cat exhaust flow. People talk about messing with the front O2 on this car, not sure why that matters. Front O2 is pre-cat and basically adjust lean/rich. Rear O2 measures the cat's cleaning efficiency.

Any words of wisdom on this particular car's P0420 code would be appreciated.

 

Cool explanation! Perhaps the 2012 recall repair didn't set it right or became loose again over time.

Any thought on how to explain the little response (turning left or right) as one begins to turn from centered wheel? Imagine the steering wheel turn like good 10-15 degrees before wheel starts turning. It does this when turning left or right from center.

 

I agree, if oil consumption is not from clogged PCV or leak, I probably won't touch it. My repair motivation haven't graduated to engine tranny builds yet haha.

Any easy way to run compression test on this car to check the rings+valves? How does one predictably crank the engine while disabling spark+fuel on these hybrids? Don't have a leak down tester ATM so compression is best I can do.

Are worn head or rings common on gen1 Prius at these miles? I realize we don't have the full service history on this vehicle. Just wondering what the statistics are.

 

Yes, had the same picture in my head. Thanks for the confirmation. Symptoms suggest that nut is definitely loose. I'll see if the local Toyota dealer would honor a free fix since they did the steering nut recall in 2012.

 

An update on this thread...

Took this Gen 1 Prius home and put it up on ramps to have a good look. I also have Toyota TechStream software + Chinese clone dongle so I took more time to snoop around the car's computers. Here is what I found

Oil consumption

There is a fresh oil leak along the edge of the timing chain cover facing the cabin. I would guess either valve cover, timing chain cover or some other sealed surfaces (a plug?) in that area. Need to clean the area up and also look at a diagram to see more detail.

This is good news, likely this is majority of the oil consumption and not the cylinders.

Steering

Did a bit more detective work here. Steering does respond from center with minute input. Had the car on ramps and can see the tie rods move with the slightest of inputs. It seems the hard to turn left turn is caused by the power assist motor. Also the steering wheel doesn't return to center on left turns. Right turns have no problems.

I was able to clear the EMPS's C1521/C1522 code and have it not come back. I did get C1571/1572 code (Vehicle Speed Sensor) in EMPS a couple of times. ABS light flashed. Cleared it both times and it didn't come back. Not sure if just related to using the diagnostic tool.

Perhaps the most strange thing is I couldn't connect to EMPS to get live data reliably. It would connect and disconnect within few seconds. I had no problem connecting to any other computer (Engine and ECT, HV Battery etc..)

So it seems my problem might not be the pinion gear nut. Rather, the torque sensors, EMPS ECU, or the power assist motor itself.

After all this, I offered the owner $500 and we have a deal. So now I have gen 1/2/3 Prius Here is the list of fixes for this gen1

- EMPS
- oil leak in passenger corner of the engine
- broken center dash panel (found this excellent thread Replacement Center Dash Panel | PriusChat)
- P0420 code. Cleared it and hasn't come back yet
- CEL light bulb out

 

Thanks for the great idea Chap, I also thought of disabling EMPS as a test. Getting the car tonight and will report back findings. Thanks for the suggestion

A bit more detail on my rack pinion play diagnoses. I had the front tires up on ramps so not floating off the ground. A buddy was looking underneath the car closely and told me there is tie-rod and tire movement with the slightest steering wheel input. If I turn it further, I can hear my metal ramps twist just a bit on the garage cement floor.

BTW, a couple of questions on EMPS ECU

- Is EMPS ECU failure common? I noticed Toyota has a campaign back in 06 to replace 01 EMPS ECUs (priuschat.com/attachments/lsc-30d-pdf.9744) I have seen a lot of car ECU failures from around 2000 all due to poor transition to lead free soldering (initial formula became brittle with vibration which is obviously not good for car application). I've fixed quite a few just by reflowing new solder (01 Rav4 ECU, 00 Volvo power seat ECU, 02 Volvo instrument panel ECU, 01 Volvo ABS ECU)

- I see some EMPS ECU on sale on ebay. Is exact part number interchangeable amongst 01-03? I read someone changed an 01's rack with 03 and it didn't talk to the 03 ECU.

BTW, saw your link on how to remove the center dash panel (Replacement Center Dash Panel | PriusChat) Going to try to recover one without damage from parts car instead of $150!

 

An update

Pulled the 50A EMPS fuse and test drove the car. Left turns are definitely harder and doesn't self center. Right turns work as advertised. So the pinion gear nut must be loose.

Local Toyota dealer did the pinion nut fix 25k miles/3 years ago for the previous owner. Called both dealer and national service desk and were told recall work is warrantied for 1 year so I guess I have to do this myself.

Local dealer service advisor was kind enough to email me the adj/lock nut service directions. Need to drop subframe to get rack out and a tool to hold the adj nut while torquing down the lock nut.

 

Here is an update.

Jacking the front end off the ground and tested the following

1. Turn steering wheel left and right. Generally, there is slightly more resistance going left
2. Hand twisting the tire/wheel as if turning the car left and right. Turning left is possible. Turning right jams tight and unable to move it regardless which angle the tire is pointing

It makes sense the pinion adjustment nut is incorrectly set and pinion gear has vertical play. Steering wheel left turns and hand twisting the tires to a right turn is creating the same mechanical pressure point inside the pinion gear assembly.

Since by hand can not twist the tires to turn right. It is clear this is also the reason car doesn't recenter after a left turn.

It appears the local Toyota dealer did quite a shoddy job on the recall

- They didn't center the rack properly (from center : 1.5 turns to left stop. Nearly 2 turns to right stop)
- The 2 steering motor codes and funky non linear steering I had prior to my own recalibration (got rid of all the non linear steering feels generated by the motor) suggest they didn't recal after the rack install
- My current loose adjustment nut issue is likely inproper torque

Too bad Toyota won't honor this shoddy work. I guess I'm left with either putting in a used/rebuilt rack or trying to adjust the nut myself.