How to catch when codes are thrown in logging?

[kwhiteside]

A buddy of mine is getting intermittent
P0171 - Fuel Trim System Lean Bank 1

How would I log for that so we could see what is going on when the code actually hits?

[joecar]

That's hard...

For some DTC's you can see the PCM manipulate some parameters (for example for P0420 you can see the commanded AFR do some strange transitions after you coast down to a stop from a freeway run)...

You would need knowledge of what conditions trigger the test to run, and what conditions cause it to fail, and then look for these in a log... the GM serviced manual lists the test trigger conditions and the test fail conditions in detail.

[gmh308]

Also you could read the "freeze frame" data out. This is a snapshot of what is happening when the DTC is posted. i.e. speed, map, pedal, rpm, phase of the moon, etc etc. Many items.

Usually for Fuel Trims to post lean it means that the LTFT is hitting max rich and still not getting the mixture into stoich.

Mostly GM seems to set max rich to 1.25 or 25% rich. To post the DTC means that it wants 30 or 35 for example. You get the picture.

[ChipsByAl]

It would help if you could view the freeze frame or failure record data. This data is a PCM saved single frame snapshot of the condition when it happened. You could then tell if only one bank was way out of range or the other was imminent of setting a lean code as well. If it appeared as if both banks were very lean, look for something that is shared. This would be fuel pressure, fuel quality, MAF, MAP, etc. If only one bank is lean and the other is OK, check for bank only problems. This could be a leaking intake/exhaust manifold or gasket, O2, or misfire on that side.
Al

[joecar]

Ken,

Those two are ahead of me...:cheers:...Freeze Frame data is saved whenever a DTC sets.

[kwhiteside]

How do you read out that freeze frame data?

Probably should do some logs on his car and watch the LT Fuel Trims. If they are both frequently putting out over 15, then it could be tune or could be some mechanical fuel shortage. If it's isolated to one bank, most likely a leak or bad injector.

[joecar]

From scantool, connect to vehicle, then go Info->History Freeze Frame Data.

Each FF says which DTC it was for.

[gmh308]

From scantool, connect to vehicle, then go Info->History Freeze Frame Data.

Each FF says which DTC it was for.

And here is a FF snapshot (maybe it was the CAT TEMP being 76,000 deg C that popped the DTC?):


[DTCS]
P0106=ECM,-F--X--S
P0107=ECM,-F--X--S
P0315=ECM,-FPHXNCS

[ECM Freeze Frame 0]
DTCFRZF=P0107
ODOFIRST=40km
ODOLAST=40km
FFCOUNT=0Count
FFPASS=0Count
FFNOTRUN=0Count
FUELSYS1=OL-Drive
FUELSYS2=OL-Drive
LOAD_PCT=8.2%
ECT=89°C
SHRTFT1=0.0%
LONGFT1=-6.3%
SHRTFT2=0.0%
LONGFT2=-5.5%
FRP=399.0kPa
MAP=10kPa
RPM=2022rpm
VSS=79kmh
SPARKADV=-0.5°
IAT=26°C
MAF=7.6g/s
TP=16.5%
AIR_STAT=OFF
O2S11V=0.000V
SHRTFT11=0.0%
O2S12V=0.445V
SHRTFT12=99.2%
O2S21V=0.000V
SHRTFT21=0.0%
O2S22V=0.450V
SHRTFT22=99.2%
PTO=Off
RUNTM=150s
EGR_PCT=0.0%
EGR_ERR=0.0%
EVAP_PCT=0.0%
FLI=0.0%
WARM_UPS=1Count
CLR_DIST=41km
EVAP_VP=0.0Pa
BARO=98kPa
CATEMP11=76460.0°C
CATEMP21=79260.0°C
VPWR=13.073V
LOAD_ABS=5.5%
EQ_RAT=1.000EQR
TP_R=3.9%
AAT=23°C
TP_B=16.5%
APP_D=18.8%
APP_E=8.6%
TAC_PCT=5.5%
E85R=0.0%
ACC=Off
ACCWOTD=Enabled
ACCPRSD=Disabled
ACREQ=Off
ACHSPS=Inactive
ACLSPS=Inactive
ACREC=Off
BPIT=Off
BPITF=Off
BPMT=Off
BPMTF=Off
BPA=Active
BPSW=Active
EBPSW=Inactive
REVINH=Inactive
REVSW=Off
UPSHIFT=Off
SSLAMP=Off
SSSOL=Off
CPTOP=OK
CPBOT=Failed
EOLVL=Low
EOLVLF=Low
EOLVLI=Off
EOPRS=Low
EOPRSF=Low
EOPRSI=Off
EOCHGI=On
CANVENT=Open
COLDST=No
FVL=Low
FWDLOW=Inactive
FWDLOWF=OK
FWDMODE=Inactive
RAXLOW=Inactive
CKREQ=Inactive
ACCES=Inactive
PTRLY=On
STRLY=Off
REMST=No
PTOREM=No
ATPN=Inactive
FTLE=Disabled
FCLA=Closed
PEA=Inactive
HCEA=Inactive
DFCOA=Active
FPO=On
SFPO=Off
CPA=Inactive
PTOFI=Inactive
FISW=Inactive
FISWS=OK
PTOESW=Inactive
PTOSW1=Inactive
PTOSW2=Inactive
PTOSWS=OK
PTOREM=No
EGR=0.0%
ECT1ST=93°C
FPUMPDC=100.0%
FTC=15Cell
IDLERPM=648rpm
$1297=$FD01
ETCPED=0.0%
ETCTP=5.4%
INJPWB1=1.0ms
INJPWB2=1.0ms
KNKRET=0.0°
TPDES=5.5%
APP=0.0%
FUELREM=0.0l
AIVON=No
AIVSHG=Failed
AIVOP=Failed
AIVSHV=Indeterm
AIPON=No
AIPSHG=Failed
AIPOP=Failed
AIPSHV=Indeterm
VSSON=Yes
VSSSHG=Passed
VSSOP=Indeterm
VSSSHV=Passed
OFFTIME=20s
VHSON=Yes
VHSSHG=Indeterm
VHSOP=Indeterm
VHSSHV=Indeterm
RPMCAM=2023rpm
RPMCKP=2021rpm
O2H11ON=Yes
O2H11SHG=Passed
O2H11OP=Passed
O2H11SHV=Passed
O2H12ON=Yes
O2H12SHG=Failed
O2H12OP=Failed
O2H12SHV=Indeterm
O2H21ON=Yes
O2H21SHG=Passed
O2H21OP=Passed
O2H21SHV=Passed
O2H22ON=Yes
O2H22SHG=Failed
O2H22OP=Failed
O2H22SHV=Indeterm
ENGOILP=268kPa
VREFA=233Count
VREFB=233Count
PTRVOLT=13.1V
CCSW=OK
CCACTIVE=No
CCCANCEL=Inactive
CCDEC=Inactive
CCINC=Inactive
CCRES=Inactive
CCSET=Inactive
CCONSW=Inactive
AFMAON=No
AFMASHG=Failed
AFMAOP=Failed
AFMASHV=Failed
AFMBON=No
AFMBSHG=Failed
AFMBOP=Failed
AFMBSHV=Failed
AFMCON=No
AFMCSHG=Failed
AFMCOP=Failed
AFMCSHV=Failed
AFMDON=No
AFMDSHG=Failed
AFMDOP=Failed
AFMDSHV=Failed
EOT=-40°C
$1559=$00
$155A=$C0
$157A=$0000
EXPHAB1=0.0°
INPHAB1=0.0°
EXPHAB2=0.0°
INPHAB2=0.0°
EXPHDB1=0.0°
INPHDB1=0.0°
EXPHDB2=0.0°
INPHDB2=0.0°
TFT=0°C
TOS=0rpm
TCRATIO=1.00:1
$1A2D=$FF00
$2002=$0A
$2005=$45
IAT2=0°C
IMTVDC=0.0%
SCBDC=0.0%
$200E=$0000
$200F=$0000
$201F=$00
$2027=$00
$2029=$00
$2050=$0000
ACCEP=0.0%
$2822=$00
GENFDC=18.8%
DESTQ=0.0%
TRACTRQ=0.0%
TTQRET=0.0°
ETCTPS2=0.824V
ETCTPS1=4.157V
ETCPPS2=0.431V
ETCPPS1=0.941V
MAFFREQ2=3037Hz
TRQDES=0.00Nm
TRQTRANS=64.96Nm
TPMIN1=0.608V
TPMIN2=0.608V
TADC=22.4%
GENLDC=100.0%
$2000=$06
$2003=$00
$2007=$00
$200C=$3F
$200D=$3F
$2028=$00

[ssvolvo]

What are we tweaking on?

Maybe of some help here:
http://service.gm.com/gmspo/mode6/index.html


John

[joecar]

And here is a FF snapshot (maybe it was the CAT TEMP being 76,000 deg C that popped the DTC?):


[DTCS]
P0106=ECM,-F--X--S
P0107=ECM,-F--X--S
P0315=ECM,-FPHXNCS

[ECM Freeze Frame 0]
DTCFRZF=P0107
...
MAP=10kPa
RPM=2022rpm
VSS=79kmh
SPARKADV=-0.5°
IAT=26°C
MAF=7.6g/s
TP=16.5%
...
lol, that's a misinterpretation of that field...

the DTC is P0107...

MAP=10kPa is too low noting that throttle is not closed TP=16.5%

See: http://www.ls2.com/boggs/dtcs/DTC%20P0107.htm

Oh, I see you found how to read DTC's from V2 itself... :cheers:

[kwhiteside]

Those are just samples to show me what a freeze frame looks like.

The Car is a CTS-V with a LS7 motor.