DME Readings Range 1 and Range 2

Hi there, I got a C2 996 with 1999 spec and exchange engine from 2008. I just read my DME data and I wondered why Range 1 Cylinder 1-3(TRA) and Range 1 Cylinder 4-6(TRA2) are a bit high, they should be 0 +/- 0.1 - correct? I recorded data during a short trip and these values were always hovering around 0.3 with only very slight deviations (think 0.29 was the lowest value). Range 1 Cylinder 1-3(TRA) ----- 0.33 Range 2 Cylinder 1-3(FRA) ----- 0.96 Range 1 Cylinder 4-6(TRA2) ----- 0.30 Range 2 Cylinder 4-6(FRA2) ----- 0.93 Could anybody help me what this means (getting some wrong air?), if and what I should do? I also pasted a full snapshot of the DME readout below. Best wishes, Wintermute A/C request ----- Open Disturbance switch ----- Closed Fuel reserve signal ----- On Full load recognition ----- Closed Idle recognition ----- Open Reference mark signal ----- Not present Start enable switch ----- Open Transmisson coding ----- Manual transmission coding Oxygen sensing, cylinders 1-3 ----- 0.99 Oxygen sensor voltage ahead of catalyst converter ----- 0.10V Range 1 Cylinder 1-3(TRA) ----- 0.33 Range 2 Cylinder 1-3(FRA) ----- 0.96 Oxygen sensing, cylinders 4-6 ----- 1.01 Oxygen sensor voltage ahead of catalyst converter, BANK 2 ----- 0.10V Range 1 Cylinder 4-6(TRA2) ----- 0.30 Range 2 Cylinder 4-6(FRA2) ----- 0.93 Air mass ----- 13504kg/h Ambient pressure ----- 840mbar ECTS ----- 94.50�C Engine compartment temperature ----- 41.25�C Exhaust temperature after catalytic converter ----- 336�C Hot film MAF ----- 1.27V IATS ----- 34.50�C Ignition timing ----- 7.50� CRK Injection time ----- 2.95ms Load signal ----- 1.10ms Oil temperature ----- 94.50�C Rpm ----- 800rpm Specified air adaptation ----- -1kg/h Specified air mass ----- 17kg/h Speed ----- 0km/h Throttle plate angle ----- 0% Voltage ----- 13.21V Camshaft position 1 deviation ----- 3� CRK HO2S heating Resistor ahead of catalyst converter ----- 3.23Ohm Learn Progress, sensor Wheel adaptation ----- 0.00 Misfire detection ----- Not Active Rough running ----- 0L/s� Rough-running threshold ----- 8.80L/s� Segment(A) ----- 0.10 Segment(B) ----- 0.10 - - - - - - - - - - - - - - - - - -

I also have the corresponding fault codes: 27 1/2 State: Current Oxygen sensing range 1 Cylinder (1-3) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 35 2/2 State: Current Oxygen sensing range 1 Cylinder (4-6) Could either mean the mixture is too lean or too rich. In my case (value being too high) it would mean it is too rich, right? Or is it like a lambda value, i.e. richer is lower? Then it would be too lean and I might have an intake system leak?

With TRA readings of 0.3 it means the DME is ADDING injection time to compensate for lean condition. At 0.36 it will set a fault code. IF it were a negative (-0.3) it is usually a failed MAF sensor but being a positive it still could be a failed MAF (in the other direction), but most likely you will find a vacuum leak or failed AOS. Test the AOS with manometer, and if OK then smoke test the intake.GL

Thank you very much, that helps! Will post here what I find out, but can take a while ;-)

Hi there, did the test with the manometer (1 manometer interface connected to the oil filler pipe, the other open). Vacuum built up to 11.2 inH2, then it hovered around that value (+/- a few .x). Guess that is over the top and the best guess would be a failed AOS? I do not have other symptoms though, engine running fine I would say. (Also no smoke, no out of spec oil consumption). Best, Wintermute

Quotes source post: 17430039

Definatly a failed AOS. Take a look at my UAOS system, it is the upgrade to solve the AOS problems that have plagued the 996 for two decades . www.ultimateaos.com

Thank you very much again! Your UAOS looks certainly interesting, great job! Will need to think about whether I go for AOS or UAOS and whether I do it myself or let a workshop do it.

Dear all, I got a new AOS, the vacuum is now approx -5.1 inH2, which is fine now, correct? Interestingly the engine seems to run a bit quiter now. Does that make sense? Unfortunately the TRA readings are unchanged, thus I will search for a vacuum leak. It could be anywhere after the MAF sensor, right? Best regards Wintermute

Quotes source post: 17522150

Hah - I resetted the fault memory and drove another round, now the values are fine! Approx 0.1 Range 1 and 1/0.95 Range 2. Yeah :-)