p0170 with freeze frame data - Page 2 - Mercedes-Benz Forum
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#11 (permalink) Old 11-05-2012, 11:54 PM
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Originally Posted by ruggler View Post
Thanks dr.x. There is a lot of conflicting info on this site with regards to this code, such as its a bad maf, o2's vaccuum leak.... So you think it's injectors, an intake air leak or engine wear? That's what the link says. Does any of that freeze frame data give you any clues what it could be or is it useless information?
You're welcome. I agree about misleading info on this forum, so you have to filter out advice from people who use Google mechanic to diagnose their cars, as opposed to a manual published to guide MB technicians using diagnostic strategy.

Start with what the manual says to do, and you should waste less time and money on replacing functioning parts.

Your freeze frame data does not indicate faulty O2 sensors. All the voltages are within range, and those lines say "fail" only because your software lacks the normal-range data.

Can you clear the code, and if so, how long does it take to come back? Maybe you can pass the emission test that way.

In the absence of helpful codes, go to chapter 12 under the "engine has uneven idle" section.
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#12 (permalink) Old 11-06-2012, 07:39 AM
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I can clear the code. Last time it took 15 mins of driving, the time before it took at least an hour of driving but the monitors wont be ready before the code pops up unfortunately. is there a ltft test or graph I can run to check to see what is going on? because the numbers on the freeze frame are within in spec am I right?
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#13 (permalink) Old 11-06-2012, 03:09 PM
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As I just said, the freeze frame numbers are within normal range (spec).

I looked up "engine has uneven idle" and it said "injectors, intake air leak".

Check your intake air system for cracks and faulty seals. You can test the resistances of the injectors on bank 1, but to check the injection times you'll need an oscilloscope. Your local mechanic has one.
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#14 (permalink) Old 11-06-2012, 05:10 PM
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Yes I am going to check for vacuum leaks this friday night and for any leaking injectors or anything else suspect. I am going to go for a drive with the scanner monitoring to see if anything else pops up.. I'll try to get to the test on the orange wire as well. I find it weird it would throw a fuel trim code when the fuel trims are in spec... Also I am guessing since the #'s are negative, it means the PCM is trying to reduce fuel due to a rich condition? Im totally new to the idea of fuel trims. I've been reading up when I have time.

Last edited by ruggler; 11-06-2012 at 05:15 PM.
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#15 (permalink) Old 11-06-2012, 07:20 PM
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Your fuel trims are ok. Mine bounce from 0.0 to like -0.8 to +0.8. I know you were driving at the time. Post fuel trims at idle. All yours look lean but i know they are a snap shot. They are also slightly uneaven and mine went very uneaven when the cats were plugged.
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#16 (permalink) Old 11-07-2012, 02:32 AM
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Originally Posted by ruggler View Post
Yes I am going to check for vacuum leaks this friday night and for any leaking injectors or anything else suspect. I am going to go for a drive with the scanner monitoring to see if anything else pops up.. I'll try to get to the test on the orange wire as well. I find it weird it would throw a fuel trim code when the fuel trims are in spec... Also I am guessing since the #'s are negative, it means the PCM is trying to reduce fuel due to a rich condition? Im totally new to the idea of fuel trims. I've been reading up when I have time.
Both your STFT and LTFT are running rich and with that the ECU is taking fuel away (shorter injection pulse).

Possible cases are:

Excessive EVAPORATIVE fumes
Open EGR vave
Clogged CATS
High fuel pressure-faulty fuel filter
Clogged air filter
Faulty MAF sensor-possibly but usually faulty on lean issues
Injectors leaking or stuck open-not likely on both banks
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#17 (permalink) Old 11-07-2012, 07:47 AM
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Originally Posted by 43sqd View Post
Both your STFT and LTFT are running rich and with that the ECU is taking fuel away (shorter injection pulse).

Possible cases are:

Excessive EVAPORATIVE fumes
Open EGR vave
Clogged CATS
High fuel pressure-faulty fuel filter
Clogged air filter
Faulty MAF sensor-possibly but usually faulty on lean issues
Injectors leaking or stuck open-not likely on both banks
Excessive EVAPORATIVE fumes- not exactly sure what this means but ill read up on it.
Open EGR-wouldn't I get an egr error code if this was the case? Ill look into it
Clogged CATS- wouldn't the calc load be really high if this was the case? I wonder if my truck falls under the recall for cats still
High fuel pressure-faulty fuel filter- just dirty? Am I able to replace it without replacing the fuel pump? I'm thinking its not the new style.
Could it be a bad fpr? I guess ill need fuel pressure gauge or will a scanner be able to find that info?
Clogged air filter-wouldn't that be sweet! Ill replace it anyways
Faulty MAF sensor-it's the original and the truck has 215,000 kms...
Injectors leaking or stuck open- I bought some Lucas fuel injector cleaner but I wanted to check if you think it's safe for this engine. Maybe the injectors are gummed up?

Should I clear the code again and take another freeze frame to compare it?

Thanks for the info so far
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#18 (permalink) Old 11-07-2012, 04:35 PM
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My trims from end of may this year before i had severe back pressure from cat on bank 1. Maff readings were low, Should have been 4.00+. O2 bank 1 sensor 2 does not react as quck as i would like and am going to change this soon.

https://www.youtube.com/watch?v=oEArsHSxTK8

Last edited by megadamp; 11-07-2012 at 04:45 PM.
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#19 (permalink) Old 11-07-2012, 05:04 PM
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Quote:
Originally Posted by ruggler View Post
Excessive EVAPORATIVE fumes- not exactly sure what this means but ill read up on it.
Open EGR-wouldn't I get an egr error code if this was the case? Ill look into it
Clogged CATS- wouldn't the calc load be really high if this was the case? I wonder if my truck falls under the recall for cats still
High fuel pressure-faulty fuel filter- just dirty? Am I able to replace it without replacing the fuel pump? I'm thinking its not the new style.
Could it be a bad fpr? I guess ill need fuel pressure gauge or will a scanner be able to find that info?
Clogged air filter-wouldn't that be sweet! Ill replace it anyways
Faulty MAF sensor-it's the original and the truck has 215,000 kms...
Injectors leaking or stuck open- I bought some Lucas fuel injector cleaner but I wanted to check if you think it's safe for this engine. Maybe the injectors are gummed up?

Should I clear the code again and take another freeze frame to compare it?

Thanks for the info so far
1. The Evap System collects the fumes stored in the fuel tank and sends it to the eng. to be burned instead of releasing it into the atmosphere.

2. There is no code for a stuck open EGR valve. Two ways of check if it is open

a. remove the large nut that connects the tube to the EGR valve and connect a large hose that fits over the EGR valve opening and blow through it. If you can it is open.

b. remove the vacuum hose to the EGR and connect a hand vacuum pump to the diaphram. While the eng. is running operate the pump and if the eng. stumbles or stalls the EGR is OK. If nothing happens the EGR is stuck open.

3. The fuel filter also houses the pressure regulator. Fuel pressure at idle should be 55-60 psi. If it is higher than that replace the filter. But if you don't have the upgrade you have to do it anyway.

4. Recall on cats. were only for faulty welds at the seams and would have no bearing on your problem. At 16 MPH there isn't very much load.

5. Stop clearing the codes. When you shut of the engine and then start it again a new event starts. If the fuel trim numbers are not within specs, the CEL will illuminate. If the problem has been corrected the CEL will not illuminate. It's as plain as that, so again stop clearing the codes.

Clear the codes after the problem has been corrected.
Attached Files
File Type: pdf EVAP System Function.pdf (37.4 KB, 30 views)

Last edited by 43sqd; 11-07-2012 at 05:30 PM.
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#20 (permalink) Old 11-07-2012, 05:13 PM
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And as 43 states it may take a while before codes are set so you will need to drive it to get the codes. Best not clear codes unless advice requires it.
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