2001 Prius. ICE will not shut off.

The engine has to be fully warmed up and the traction battery SOC has to be at an acceptable level, before the engine will shut off at a stop.

32 mpg is not very good, but over what distance and at what speeds was this reading developed? If this mpg reading was taken over a short distance, try taking a highway road trip of 100 miles or more, at 65 mph or less, and see what happens. Ideally you'd register mpg in the low-40s.

If you don't have any warning lights on then you might check the following:

1) engine oil not overfilled, viscosity 5W-30
2) check tire air pressure. 35/33 psi is spec, I use 44/42 psi.
3) raise rear axle and spin rear wheels when parking brake disengaged, checking for drag
4) check wheel alignment
5) check iridium spark plug condition and replace if gap > 1.1 mm. Change interval is 60K miles

At 220K miles it is certainly possible that the gasoline engine has worn to the extent that it is less efficient than when new. You could try a cylinder leakdown test to assess the condition of the piston rings and valve seats. Good luck.

 

Just a few obvious things I didn't see mentioned...

First of all, are you running the air conditioner? That will keep the engine running this this model has a belt-driven A/C.

Also, it takes a good 5 minutes for the engine to warm up to operating temperature. During the first 5 minutes it is normal to see fuel economy in the area of 20 to 35 mpg. If that sounds bad, just imagine what a big SUV gets when its engine is cold, the only difference is their vehicles don't tell them about it.

As was also mentioned before, the engine will not shut off until it has reached operating temperature.

 

The MFD shows a battery graphic and a rough indication of traction battery charge. The battery graphic has four bars, and will typically show two or three bars.

When you see zero bars, the battery is ~40% charged and when you see four bars the battery is ~80% charged. Hence, two bars on the graphic means ~60% charged while three bars on the graphic ~70% charged. These are rough approximations as the gauge is not linear.

You asked how long it takes for the engine to warm up. adric already pointed out that mpg for the first 5 minutes will be depressed due to the engine warming up, and the engine ECU briefly retarding ignition timing to encourage catalytic converter warm up.

Further, when the engine is cold you'll see a blue thermometer icon. (When overheated you'll see a red thermometer icon.)

 

It isn't always clear but defrost is the same as AC. Subtle but it has bit a few.

WARM-UP

If you can, drive the first 1-2 miles at neighborhood speeds, ~25 mph, and shift into "N" when you don't need power. The goal is to avoid asking the engine to do much as it warms up. At the end of the warm-up phase, try to find a place to come to a complete stop for ~30 seconds. When the engine stops, you are in Phase 4, full hybrid mode.

NORMAL DRIVING

Try to say at 65 mph or slower; climb hills at 55 mph if possible; avoid accelerating up hills; try to stay under 39 mph if feasible so the engine can stop and traction battery power be used. Try to drive as if you have no brakes but don't hesitated if needed. For example, if approaching a red light, brake early (traffic permitting) so you have more time to coast to the light. Mostly, don't worry about it but drive the car safely.

LAST MILE

If you can, approach the last mile or two at 30 mph or less. This helps to use traction battery power to save fuel. If it is hot, park in the shade. If it is cold, park in the sun.

Do you have a scanner of some type? Any codes?

Thanks,
Bob Wilson

 

Fill up the tank and reset the trip A and see what the mpg will say.
Likely you still have the old trip/tank reading after your repair.

 

Mostly I was wondering if you had one. Some of cheap ones can provide engine rpm and this can be helpful for efficient driving. Right now, there is one scanner that is OK but not perfect, yet.

Commercially, Auto Enginity is usable and provides diagnostics codes. It is not fully there for engineering data studies but I continue to work with the vendor. At $300 and adding your own laptop, it is expensive but a usable, diagnostic device. The problem is a laptop can lead to distracted driving so it is not a recommend, 'drive-by' instrument unless you get one of the subminature windows boxes. However, it can read the individual, traction battery, module pairs.

Some folks have had limited success with the Scantool but I've not tried that one. It takes more programming but it has the advantage of a standalone device. Call it a work in progress. It can provide engineering units but I don't think it reads diagnostic codes, yet. Someone posted codes that allows reading the individual module codes however the display is limited in size

We don't have a great solution like the Graham Miniscanner, which does both. Sad to say, it is no longer in production.

Bob Wilson