PO171 - Toyota Yaris Forums

bronsin · 04-30-2011, 06:26 PM

My sons 2000 ECHO threw this code. Possibe problems: MAF and vacuum leak. We had cleaned the sensor previously but the code came back. We looked it over good today for a leak but found none. So I thought "Price a MAF and change it". Rebuilt its $109. At the parts place i ask the guy: Is the MAF for a 2000 ECHO and a 2009 Yaris the same thing?" They are! BING! So we swapped myin into hisn and hisn into myin. After an hour his had no code stored (we cleared the PO171 by disconnecting the battery.) After an hour mine has a PO101 code ("pending") which is specificially a MAF problem code.

But...is an hour long enough to ensure a code will or will not be thrown? And whasat "pending" mean? The CEL is NOT on.

Thanks!

Focus_Sh1ft · 04-30-2011, 08:39 PM

P0101 is almost certainly a vacuum leak. I had the same issue.

P0171 is either system too rich or lean... can't remember. I doubt the MAF is the issue. It's most likely also a vacuum leak, but could be the front O2 sensor.

bronsin · 04-30-2011, 09:52 PM

I looked up PO101 in the ECHO service manual. It says MAF. It doesnt say vacuum leak. And the code was thrown in my Yaris. We didnt get a code in his ECHO. But I dont know how long it takes the engine to read and throw the codes. Possibly one of the isues you mention might be thrown in time. But...it would seem the ECHO MAF now in the Yaris is to blame from what I see so far...

Focus_Sh1ft · 05-01-2011, 12:02 AM

Alright I just re-read your post - are you saying you put his MAF in your Yaris and THEN it threw a P0101 code? And it threw P0171 while in the Echo? If so, I'd do continuity and voltage checks on the MAF pins. They specs are somewhere in the service manual - I'll see if I can find them.

bronsin · 05-01-2011, 06:18 AM

Yes that is what I did. I switched MAFs. The one in the 09 Yaris into the 00 ECHO and the 00 ECHO MAF into the 09 Yaris. The ECHO had a PO 171 code thrown prior to that and the CEL was on for about a year and a half. I had cleaned the ECHOs MAF with spray electronic cleaner about a year previously, but it still threw the code. I did not use my scan gauge to check the Yaris before I made the switch, but its CEL was never on at any time prior to that.

The MAF then threw the PO101 code in my Yaris. After an hours time with the engine running. Wait a minute. The CEL in the Yaris never came on. But I SCANNED the Yaris and got a PO 101 code and the gauge said it was PENDING. I do not know what that PENDING means.

I do have the ($140) service manual for the ECHO. I wonder is the specs for the MAF sensor in there? According to the parts guy at Sons Auto the MAFs are the same ECHO to Yaris. I will look. The index sucks however so that might be difficult.

What was your idea about the electrical properties of the MAF? What might be wrong? Based on what I did switching the MAFs I was going to order the rebuilt MAF (what does "rebuilt" mean and is that a good idea to install one?) from Sons Auto today $109. But if the suspected MAF could be fixed I would rather not spend the $$$ (cheap huh?)I DID see the two wires down inside the hole and they looked to be unbroken. They were not as shinny as the MAF wires were from the Yaris.

Thanks for any illumination on this subject!

bronsin · 05-01-2011, 06:36 AM

I found the page in the Service Manual about the MAF. It says to measure the resistance between terminals EA and THA and at 68 degrees F that should be 2.21-2.68 ohms. Thats with the MAF out of the car. With the MAF removed from the car but still attached to the wiring harness, you turn on the ignition and measure the voltage across terminals VG (+) and E2G (-) while blowing through the hole in the end of the MAF so simulate airflow. The voltage should fluctuate. Since the ECHOs MAF is now in my Yaris when i go to work on Monday I will remove it from the car and give it to our testers at work to measure it up for me.

I guess the MAF from the ECHO must be shot but the test would confirm it. I never came across this info in the manual all this time. Nor have I ever heard its possible to test it in any source from the internet. (although I have read you can clean it)

OH PO 101 in the ECHO Service Manual specifies MAf sensor and doesnt say anything about a vacuum leak. Specifically "Mass Airflow Circuit Range/Peformance Problem. It says "DI 26" under where it says "PO 101".

Di 26 has a whole rigamoroll about testing the MAF or more accUrately testing the air temp sensor which is a thermistor in the MAF. Which I kinda dont understand. But it would seem switching MAF from ECHO to Yaris and reading the codes (or lack of codes) would be an equally valid test.

But...the ECHO is throwing PO 171 (which lists about five possible troubles) and the Yaris is "pending" PO 101 (which only talks about the MAF.

Interesting. Im learning a lot here.

Focus_Sh1ft · 05-01-2011, 01:00 PM

Ok I understand the situation now. If P0101 is pending, that means a drive cycle has been completed and the ECU has detected a potential issue. A CEL isn't thrown until a set number of drive cycles is completed and the potential issue is present for all of them. Every code has a different required number of drive cycles necessary (and I believe a drive cycle is about 10 miles give or take). If I remember correctly, P0101 requires 2 drive cycles.

So what I would do from here (since you seem to have a code reader) is clear the pending codes in the Yaris. Keep the Echo MAF in the Yaris and do a decent amount of driving. If P0101 sets in then it's most likely the MAF. One other thing - does your Yaris have an aftermarket intake?

bronsin · 05-01-2011, 02:03 PM

Quote:

Originally Posted by Focus_Sh1ft

One other thing - does your Yaris have an aftermarket intake?

No it is completely stock. So is the ECHO.

04-30-2011, 06:26 PM	#1
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	PO171 My sons 2000 ECHO threw this code. Possibe problems: MAF and vacuum leak. We had cleaned the sensor previously but the code came back. We looked it over good today for a leak but found none. So I thought "Price a MAF and change it". Rebuilt its $109. At the parts place i ask the guy: Is the MAF for a 2000 ECHO and a 2009 Yaris the same thing?" They are! BING! So we swapped myin into hisn and hisn into myin. After an hour his had no code stored (we cleared the PO171 by disconnecting the battery.) After an hour mine has a PO101 code ("pending") which is specificially a MAF problem code. But...is an hour long enough to ensure a code will or will not be thrown? And whasat "pending" mean? The CEL is NOT on. Thanks! Last edited by bronsin; 04-30-2011 at 06:37 PM.

05-01-2011, 06:36 AM	#6
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	I found the page in the Service Manual about the MAF. It says to measure the resistance between terminals EA and THA and at 68 degrees F that should be 2.21-2.68 ohms. Thats with the MAF out of the car. With the MAF removed from the car but still attached to the wiring harness, you turn on the ignition and measure the voltage across terminals VG (+) and E2G (-) while blowing through the hole in the end of the MAF so simulate airflow. The voltage should fluctuate. Since the ECHOs MAF is now in my Yaris when i go to work on Monday I will remove it from the car and give it to our testers at work to measure it up for me. I guess the MAF from the ECHO must be shot but the test would confirm it. I never came across this info in the manual all this time. Nor have I ever heard its possible to test it in any source from the internet. (although I have read you can clean it) OH PO 101 in the ECHO Service Manual specifies MAf sensor and doesnt say anything about a vacuum leak. Specifically "Mass Airflow Circuit Range/Peformance Problem. It says "DI 26" under where it says "PO 101". Di 26 has a whole rigamoroll about testing the MAF or more accUrately testing the air temp sensor which is a thermistor in the MAF. Which I kinda dont understand. But it would seem switching MAF from ECHO to Yaris and reading the codes (or lack of codes) would be an equally valid test. But...the ECHO is throwing PO 171 (which lists about five possible troubles) and the Yaris is "pending" PO 101 (which only talks about the MAF. Interesting. Im learning a lot here. Last edited by bronsin; 05-01-2011 at 06:51 AM.

04-30-2011, 08:39 PM	#2
Focus_Sh1ft Drives: 08 Yaris Turbo; 06 tC Turbo Join Date: Jan 2010 Location: New Jersey Posts: 875	P0101 is almost certainly a vacuum leak. I had the same issue. P0171 is either system too rich or lean... can't remember. I doubt the MAF is the issue. It's most likely also a vacuum leak, but could be the front O2 sensor.

04-30-2011, 09:52 PM	#3
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	I looked up PO101 in the ECHO service manual. It says MAF. It doesnt say vacuum leak. And the code was thrown in my Yaris. We didnt get a code in his ECHO. But I dont know how long it takes the engine to read and throw the codes. Possibly one of the isues you mention might be thrown in time. But...it would seem the ECHO MAF now in the Yaris is to blame from what I see so far...

05-01-2011, 12:02 AM	#4
Focus_Sh1ft Drives: 08 Yaris Turbo; 06 tC Turbo Join Date: Jan 2010 Location: New Jersey Posts: 875	Alright I just re-read your post - are you saying you put his MAF in your Yaris and THEN it threw a P0101 code? And it threw P0171 while in the Echo? If so, I'd do continuity and voltage checks on the MAF pins. They specs are somewhere in the service manual - I'll see if I can find them.

05-01-2011, 06:18 AM	#5
bronsin Drives: 2009 Base Hatch 2 Dr Auto Join Date: Dec 2008 Location: nj Posts: 4,790	Yes that is what I did. I switched MAFs. The one in the 09 Yaris into the 00 ECHO and the 00 ECHO MAF into the 09 Yaris. The ECHO had a PO 171 code thrown prior to that and the CEL was on for about a year and a half. I had cleaned the ECHOs MAF with spray electronic cleaner about a year previously, but it still threw the code. I did not use my scan gauge to check the Yaris before I made the switch, but its CEL was never on at any time prior to that. The MAF then threw the PO101 code in my Yaris. After an hours time with the engine running. Wait a minute. The CEL in the Yaris never came on. But I SCANNED the Yaris and got a PO 101 code and the gauge said it was PENDING. I do not know what that PENDING means. I do have the ($140) service manual for the ECHO. I wonder is the specs for the MAF sensor in there? According to the parts guy at Sons Auto the MAFs are the same ECHO to Yaris. I will look. The index sucks however so that might be difficult. What was your idea about the electrical properties of the MAF? What might be wrong? Based on what I did switching the MAFs I was going to order the rebuilt MAF (what does "rebuilt" mean and is that a good idea to install one?) from Sons Auto today $109. But if the suspected MAF could be fixed I would rather not spend the $$$ (cheap huh?)I DID see the two wires down inside the hole and they looked to be unbroken. They were not as shinny as the MAF wires were from the Yaris. Thanks for any illumination on this subject!

05-01-2011, 01:00 PM	#7
Focus_Sh1ft Drives: 08 Yaris Turbo; 06 tC Turbo Join Date: Jan 2010 Location: New Jersey Posts: 875	Ok I understand the situation now. If P0101 is pending, that means a drive cycle has been completed and the ECU has detected a potential issue. A CEL isn't thrown until a set number of drive cycles is completed and the potential issue is present for all of them. Every code has a different required number of drive cycles necessary (and I believe a drive cycle is about 10 miles give or take). If I remember correctly, P0101 requires 2 drive cycles. So what I would do from here (since you seem to have a code reader) is clear the pending codes in the Yaris. Keep the Echo MAF in the Yaris and do a decent amount of driving. If P0101 sets in then it's most likely the MAF. One other thing - does your Yaris have an aftermarket intake?