2001 prius engine light, error code P0171 with miniscaner - Toyota Prius Forum : Prius Online Toyota Forums
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post #1 of 49 (permalink) Old 05-07-2007, 07:47 PM Thread Starter
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Default 2001 prius engine light, error code P0171 with miniscaner

This is the third time that I remove the ground on the battery to erase
the fault egine light.
I have this miniscaner that works grate it gives me an error P0171.
I tried the gas cap but stil the same.
On the Toyota manual it says system too lean.
Anyone of you came across this problem.
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post #2 of 49 (permalink) Old 05-07-2007, 09:28 PM
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Too lean could be a vacuume leak, stuck/dirty throttle body, bad O2 sensor, possibly bad/fouled MAP sensor, etc.
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post #3 of 49 (permalink) Old 05-08-2007, 08:17 AM Thread Starter
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Thanks for the reply.
I have a question for you what is the MAP sensor and where is located.
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post #4 of 49 (permalink) Old 05-08-2007, 12:23 PM
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Default P0171

Under the engine air filter you will see a small probe coming in from the front side. This is a mass air flow (and temperature) sensor. It (and the throttle butterfly further down) can both be cleaned, exercising the appropriate cautions.

It is not unusual for Prius to need its butterfly cleaned of soot.

If Prius also has a manifold air pressure sensor, it is not known to me. Hoping that DanMan has another comment on that.

DAS
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post #5 of 49 (permalink) Old 05-08-2007, 04:55 PM Thread Starter
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Thanks tochatihu
I looked the MAP probe is clean like new.
I looked the throttle is very clean.
I used compressed air and I saw nothing comming as a debris.
I looked all the vacuum hoses they are in perfect condition.
I think I must make some measurment to see if I can spot somthing wrong.
The car has 73000 miles most highway.
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post #6 of 49 (permalink) Old 05-08-2007, 11:12 PM
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Default Re: P0171

Quote:
Originally Posted by tochatihu
If Prius also has a manifold air pressure sensor, it is not known to me. Hoping that DanMan has another comment on that.

DAS
Repair manual for 2004 mentions it in a Part and System Name List at the beginning of the SFI section, but only as a glossery entry. Not mentioned anywhere else.
Lots of stuff on the evap vacuum stuff though, including pressure sensors. Also the way the 200-2003 handles exhaust emissions control, a leak may be from there causing false O2 readings.
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post #7 of 49 (permalink) Old 05-10-2007, 08:22 AM Thread Starter
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Thanks DanMan32
I have the 2001 service manual and it says at the end of tree pages check list the the error P0171 is fuel starvation.
I will change the fuel filter.
I updated the miniscaner's software to version 7 and I can see the o2
sensor the air mas the injectors the spark plugs and the throttel position among other things.
I run out of luck at this time.
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post #8 of 49 (permalink) Old 05-10-2007, 10:21 AM
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Default Fuel filter?

Both the fuel filter and pump are integral to the fuel tank assembly, which is an expensive part. Is there a way to confirm fuel supply to the injectors (other than the milliseconds open time that you are seeing with the miniscanner)?

In TSB EG011-03, the replacement of the FT assembly is sometimes required, but before that, the fuel pump relay. Is it also possible in this case that this relay could be at fault?

I am not certain that it could be, because the typical DTC leading to this DTC is P3191.

This TSB and the others are posted in the files section of the Yahoo! toyota-prius-sat1 group. One must join that to read the files.

DAS
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post #9 of 49 (permalink) Old 05-10-2007, 03:32 PM
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Default Just a guess...

If it turns out that the problem is fuel pump-related, I think there was a recall on older Prius's a couple of years ago where the fuel tank and pump were replaced under warranty. I seem to recall having that done on our 2002, but my memory is a little fuzzy on this. I don't think there were any error codes on our car; and I believe that the replacement was done during one of the routine maintenance procedures.

You might want to see if this recall was done on your car.
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post #10 of 49 (permalink) Old 05-10-2007, 06:59 PM Thread Starter
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Thanks for the reply Phoenix
I looked all my records but I did not find anything with the fuel pump or the fuel tank.
The car works ok except it get's the engine light and the code P0171.
The code is starvation of fuel and is the worse to fix.
The car is year 2001.
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