error code P0171

[bronsin]

Got this error code on my sons 2000 ECHO. Assume there is enogh commonality with the Yaris to make deductions valid. Book says P0171 can be:

air induction system
injector blocked
mass air flow meter
engine coolant sensor
fuel pressure
exhaust leak
opn/short heated oxy sensor bank1 sensor 1
heated oxygen sensorr

Anyone have any experience with this code? Or have any comments on how to evaluate each component listed? Im thinking its easy to check for exhuast leak.

[1stToyota]

Got this error code on my sons 2000 ECHO. Assume there is enogh commonality with the Yaris to make deductions valid. Book says P0171 can be:

air induction system
injector blocked
mass air flow meter
engine coolant sensor
fuel pressure
exhaust leak
opn/short heated oxy sensor bank1 sensor 1
heated oxygen sensorr

Anyone have any experience with this code? Or have any comments on how to evaluate each component listed? Im thinking its easy to check for exhuast leak.

Did one last week (P0171/P0174)...but it was on a Ford Windstar (front valve cover, PCV valve, isolator bolt kit & intake manifold gaskets)

On the 2000 Echo I think I'd start with a quick look at the MAF meter to see if it's dirty.

[talnlnky]

Did one last week (P0171/P0174)...but it was on a Ford Windstar (front valve cover, PCV valve, isolator bolt kit & intake manifold gaskets)

On the 2000 Echo I think I'd start with a quick look at the MAF meter to see if it's dirty.

wow... if he's having issues with the MAF then there's something way wrong with the air filter.... correct?

[1stToyota]

wow... if he's having issues with the MAF then there's something way wrong with the air filter.... correct? One of those OBDI Karman Vortex Air Flow Sensors that an ex YW member said we had on our Yaris'? Seemed like a few other members agreed about the OBDI sensor being on our OBDII Yaris. LOL

Book says P0171 can be:

air induction system
injector blocked
mass air flow meter
engine coolant sensor
fuel pressure
exhaust leak
opn/short heated oxy sensor bank1 sensor 1
heated oxygen sensorr


Best place to start :rolleyes:

[YarisSedan]

thats a system too lean code i believe. Most likely a vacuum leak causing lean condition or MAF sensor that is contaminated. First check for any vacuum leaks. Spraying carb cleaner in areas where you may suspect and listen for changes in idle to locate. Inspect all hoses that go to intake that is behind the maf sensor for cracks or brakes. If none are found then remove and inspect the sensor. Look for dirt buildup. If it is dirty you can spray it with MAF sensor cleaner or electrical contact cleaner and replace the filter if its dirty.

A faulty 02 sensor usually will trigger a code for heater circuit fault. Injectors that are restricted enough to cause a lean condition will usually trigger a intermitent missfire you should have a p0300 code along with it.

Id say the most likely cause is the MAF sensor. Especially if there is a aftermarket intake. Oiled intakes such as K&N have been known to contaminated sensors. The oils get sucked on and stick to the sensor. Then the dirt sticks to the oils and builds up on the sensitive wire.

[bronsin]

Thankyou. Thankyou. I checked the exhaust system by plugging the tailpipe with a rag. Seemed good. Checked for loose/cracked hoses all around the af housing and the local area. All good. I bought the car with 116k on it two years ago and put a Purolator AF on it then. Its pretty dirty. Has 133k now. Car has never had a KN on it. The two wires on the MAFS are dirty and rusty looking. One is oily looking. I was going to use brake cleaner fluid on the wires. That wont melt the plastic housing, will it? MAS specific cleaning fluid is $7.

[bronsin]

q

[krusty]

Some of the brake clean products out there can melt plastic you would be safer to buy maf cleaner or something that is safe on plastics.

[YarisSedan]

Wouldnt try brake cleaner. May be too harsh. Use electrical contact cleaner or MAF cleaner. 7 bucks is worth it for the piece of mind if you damage the sensor they are EXTREMLY expensive. Replaced one on my friends lexus it was 967. Not sure how much they are for the yaris probally atleast a few hundred.

[bronsin]

Yikes $967! Im cheap though so I might try just a little on the plastic and see if it melts.

[1stToyota]

I'd use MAF cleaner; last time I checked retail was close to $600.00 for new MAF sensor

[MUSKOKA800]

Yikes $967! Im cheap though so I might try just a little on the plastic and see if it melts.


:eek: You're crazy man.
It's $7.00. Less than the cost of indigestion at Rotten Ronnies.

[bronsin]

Used the brake cleaner on the MAS with no ill efects. Just sprayed it on and drained it three times. Wires came out nice and clean. Plastic was unaffected. Changed to AF also. Drove the car ten miles then let it sit and idle for half an hour. I erased the CEL with the code reader and it didnt come back on again. Is that long enough?

[bronsin]

q

[YarisSedan]

Will need to drive for about 100 miles to confirm 100 percent its fixed. Have to set all the monitors first. Light still may come on.

[bronsin]

Time will tell. I'll post the results whn they become apparent.

[bronsin]

Over 200 miles and the light is still out!

[1stToyota]

Over 200 miles and the light is still out!

I think you got 'er.