Need help understanding Durametric fuel trim readings

[Dale_K]

My 2000 S Tiptronic that I bought back before Christmas has been throwing codes indicating the motor is running lean and I've fixed one vacuum leak on the oil fill tube with one other fix pending on the line going to the brake booster. The codes are 1124, 1126 and 1130. I bought a Durametric unit that often shows an additional code of 0410.

The ODBII maintenance manual says 1126 is "Oxygen sensor adaptation range 2 (cylinders 4-6) enrichment limit". I cleared the 1126 and 0410 codes and took a 30 mile ride last evening and obtained the following readings idling in my driveway at the end of the ride. The motor seemed to run perfectly as near as I can tell. The Durametric showed "no faults" at the end of the drive. Typically the CEL comes back on after about 200-350 miles.

Loss Adaptation Idle .08

Adaptation range 2 FRA Bank 1 1.27

Adaptation range 1 RKAT Bank 1 -2.58

Adaptation range 2 FRA Bank 2 1.24

Adaptation range 2 RKAT Bank 2 -2.39

MAF sensor volts at idle 1.30

I don't understand any of the above except that the MAF sensor volts seems OK.

Are these the correct data points for monitoring long term fuel trim?

What do the terms "range 1" and "range 2" mean?

What do FRA and RKAT mean?

What are the units of measurement?

What do the values signify? What are ideal or good values on a Boxster motor that is running well? What kind of numbers would show running lean vs running rich?

Edited April 3, 2011 by Dale_K

[Loren]

P1124 is fuel pump output problem - that could cause the other codes.

When was the last time your fuel filter was changed?

[Dale_K]

P1124 is fuel pump output problem - that could cause the other codes.

When was the last time your fuel filter was changed?

I'm sorry, it wasn't 1124 - I was going off my memory about the previous codes. It must have been 1126, 1128 and 1130.

[Loren]

You have an air leak - these codes have been covered many times here.

Suspects are loose or damaged intake tube, AOS, AOS bellows, oil filler tube, etc.

[Dale_K]

The main question I wanted answered was not whether or not I have an air leak. What I want to know is how to use the Durametric to understand and monitor the performance of the car. I would be grateful if you or anyone else could shed some light on the actual numbers I posted, the measurement units, their meaning and especially numbers from the same data points on Boxster motors in tip-top condition.

[Loren]

From the OBD II manual for your car. If you want a full explanation you might consider buying a copy.

System description

The adaptation values can be read out with the Porsche System Tester 2.

The key to the adaptation values is as follows:

RKAT = Adaptation in range close to idle

Cylinders 1 - 3

RKAT2 = Adaptation in range close to idle

Cylinders 4 - 6

FRAU = Adaptation in lower load range

Cylinders 1 - 3

FRAU2 = Adaptation in lower load range

Cylinders 4 - 6

FRAO = Adaptation in upper load range

Cylinders 1 - 3

FRAO2 = Adaptation in upper load range

Cylinders 4 - 6

FR = Oxygen sensor for cylinders 1 - 3

FR2 = Oxygen sensor for cylinders 4 - 6

My understanding of range 1 and range 2 is that range 1 is the reading before the DME adapts the mixture and range 2 is after adaption.

The fault codes say you have either an air leak or a bad MAF.

Here are the correct readings for a Boxster MAF at idle AND at 3000 RPM.

[Dale_K]

Thanks. I did buy a book called the "Boxster Maintenance & ODBII Manual" thinking it would provide a detailed explanation of the car's systems, etc but it only has about 1 page per code and doesn't describe the theory of operation or the evaluation of diagnostic data. It must be a different book than the one you mention. I am interested in buying the more complete book if anyone has a link.

I guess the "LV" in "CLV" must be Load Value. I don't understand the negative values reported by the Duratmetric for RKAT data points. I guess I need that book. Somehow I was getting the impression (totally guessing) that 0 (zero) might be the ideal value for points labeled adaptation with the actual number reported being a percentage of the permissable range of compensation being applied by the DME. Minus numbers would represent one direction (lean vs rich) and positive the other. That's all guesswork lacking "the book".

The basic idea I have is that my car's failure mode (CEL stays off for a long time after clearing, car runs great) might be pointing to an intermittantly bad sensor, such as the MAF (shop wants to put on a new one.) If that was true I'd see pretty normal values from the data points except when the bad sensor was acting up. The other failure mode would be if all the sensors were working OK. Then I would expect to see data values that signify a pretty strong vacuum leak and those values would improve after each incremental repair fixed another leaking item. Obtaining and understanding the Durametric values is an attempt to see which of those two scenarios is most likely.

[Loren]

If the MAF reading changes from idle to 3000 RPM then it is likely okay.

Let me say again - you have an air leak. Many have had the same error codes as you have and 99.97% of the time it is an air leak.