OBD-II / OBD II Capabilities & Recommendations & Code P0171

Post by **1997volvo850** » 07 Jun 2010, 21:01

I did find a few old threads on OBD II tools but they did not answer my questions. I've seen an Equus tool
advertised as compatible with the 1997 Volvo 850 E203140 for $364. I'm hoping there is a tool that will
do what I want for less.

Will standard mid-level OBD II tools be able to read live data from my 1997 Volvo 850?

Here is my specific situation:

I completed several repairs to my vehicle and took it to be inspected. Since I had only driven
it 30 or so miles they said that only three monitors had set and to come back after I drive around
a 100 miles. They also told me there are pending codes.

At around 80 miles the Check Engine light comes on.

The code is the P0171 - System Too Lean (Bank 1).

I've been reading about this code on the web and there is a long list of things to check or replace. I've cleaned the MAF.
I have a new fuel filter on order and plan to check the fuel pressure this weekend. I'm also looking for vacuum leaks.
The two O2 sensors are another possible cause of the problem. I don't want to replace the MAF ($170) or the two
O2 sensors (~ $300) unless I really need to.

I can't afford to drive 100 miles each time I fix one of these items. The nearby Advanced Auto Parts store had their OBD
reader stolen so they no longer read the codes.

Some of the write-ups on the web discuss examining live data to examine the fuel mixtures. This would tell me
if I am on the right track without having to drive 100 miles.

The question is whether there is a OBD II scanner that will do this on a 1997 Volvo 850 and which costs less than $400.
Much less.

It also appears that these pending codes show up LONG before the check engine light comes on. In this case it was
pending at 35 miles and the check engine light came on at around 80.

How soon do pending codes get recorded? Even knowing the code is pending would tell me that I'm not on the right
track. It seems most basic scanners will display pending codes.

Advanced Auto Parts has the Actron 9180 scanner on sale. I've seen Equus mentioned but some have experienced
problems with these on Volvos.

Any experience? Recommendations?

Thanks

Post by **jblackburn** » 07 Jun 2010, 21:16

BEFORE you go throwing sensors and money at it, check for vacuum leaks!!!

The P0171/P0172 codes are almost ALWAYS caused by a vacuum leak, I have thrown 2 of them myself.

In my case, it was the one on the left side of the intake manifold, and a vacuum line at the front of the intake.

This is how I fixed it for short-term (it is part of the PCV system and a PITA to fix otherwise)

Post by **1997volvo850** » 07 Jun 2010, 22:35

Thanks. I checked that elbow and it looks okay. Can't reach it to feel around.
I suppose I may need to take off the intake manifold to inspect all of the PCV
system hoses. Might as well replace the PCV system while I'm at it.

When you discovered this elbow was damaged did it make a hissing sound? When I'm
driving hard I don't here any hissing sounds.

Could also be old gas and very old fuel filter. Added some octane booster. Fuel pressure check
should identify or eliminate the fuel system as a potential problem. New fuel filter (old one is
rusted bad) is on the way.

Post by **jblackburn** » 07 Jun 2010, 22:59

I heard a very loud hissing at idle with the hood closed when the one at the front of the intake let go.

The side one was only audible with the hood up, and only then if you listened for it over the noisy engine.

It may be a smaller leak somewhere, but even the smallest can set off a check engine light. If the PCV hose looks OK at both ends, then it's pretty safe to assume the middle is OK, as it runs through a fat rubber protector under the intake manifold. But inspect the hose at both ends, as well as the ones at the front of the intake and into the vacuum tree. Those seem to be the most common ones to crack, anyway, and a turbo vacuum hose will leave you with a different code or lack of power.

Post by **1997volvo850** » 08 Jun 2010, 05:31

Thanks.

So I have a few things to check:

1) Vacuum leaks. Will likely need to remove intake manifold.
2) Fuel filter and pressure. New filter on the way. Will check pressure.
3) If all else fails check/replace MAF/Sensors

Still want to verify whether the fixes I perform resolve the problem without driving 100 miles.

Examining live data (if possible) would allow me to verify problem is fixed. Seeing pending codes
would at least let me know I still have a problem.

Is anyone using an OBD II tool to inspect various system components? live data? Or is examining live data not possible?

Retired MVS Contributor · Post by **Retired MVS Contributor** » 08 Jun 2010, 07:34

P0171 is not a Volvo-specific code...It is evidently a generic code obtained with a generic reader, since it refers to "bank 1" and makes me think it is for a V6 or V8 engine...Volvo's so-called "white" engines are single-bank in-line 5 or 6 cylinder engines...

There was an excellent code reader/eraser made by BSR of Sweden and marketed in the country by Alpha-bid.com, an e-bay vendor, for less than $200...I have one of these readers...BSR's web site says that this reader, called PPC Diagnostic System, is no longer in stock because they are going to market a newer version and it will be ready soon...Check with Alph-bid.com...They might still have them in their stock...

If one visits BSR's web site, one can see a list of all Volvo-specific codes and what they mean, but the "P" codes will not be found there, only Volvo codes...Given the number of Volvo model cars, there are literally hundreds of them...

Post by **jblackburn** » 08 Jun 2010, 07:45

You can easily read live data with most scan tools, my Actron will show me MAF, O2 sensor, and throttle opening data. But if something else is causing the code other than a bad O2 sensor (vacuum leak), those readings are not going to help you.

Buy a can of carb cleaner and spray around any vacuum lines you can find before you go about taking off the intake manifold. Listen for changes in the engine RPM.

If you need to do the PCV system, then go ahead and do it anyway...you'll likely see anything cracked in the process, or like me, crack about 3 others while doing it.

If you cannot find any other cause, it's probably the front O2 sensor. You should see the voltage hover around 1.0875V at idle, and it will swing up and down as you rev the engine and let off. If you have noticed any recent downturn in gas mileage, that's also suspect.

Post by **1997volvo850** » 08 Jun 2010, 09:02

I know about the elbow on the left side of the intake [looking at engine from front] (passenger side).

So I should spray carb cleaner around that elbow, the vacuum tree, and I suppose the PCT valve. Is that
it?

I posted a picture in another thread of my badly rusted fuel filter. Since the P0171 seems to indicate more
oxygen or not enough fuel I suspect this old filter could also play a role in this. Fuel filter from FCP Groton is
out for delivery...still thinking to check gas pressure before/after the fuel filter switch just for shits and giggles.

I may pick up a mid level code reader just to be able to read the codes. My Check Engine bulb has held up
remarkably well for being on so much.

Thanks

Post by **jblackburn** » 08 Jun 2010, 09:18

Go for it. Replace the filter, reset the codes by yanking the battery cable since you don't have a scanner, and see if it comes back again.

If that doesn't solve your problem, move on to some of the other things.

Like most troubleshooting, it will take some time to track down. I hate that orange light.

Post by **1997volvo850** » 08 Jun 2010, 19:11

- Sprayed carb cleaner around elbow on left side of intake, on vacuum tree, and on PCT valve. No noticeable
reaction from car. No racing condition.

- Fuel pressure is around 38 psi. Had to remove injectors as fuel gauge coupling would not fit between throttle body and
Schroeder valve. Which seal do you normally replace after removing the injectors? It's right on the injector, right? The
ones I've seen at FCP appear to be for the rail to injector connection. Is there one for the injector to block connection.

- Still need to replace fuel filter. May try tonight.

- Still need to pick up OBD II tool.