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#2084280 - 11/22/10 05:18 PM interpreting scan data from obdII code reader
Spykem4e Offline

Registered: 10/23/08
Posts: 385
Loc: Montreal, canada
Hi guys,

I just bought on sale an Innova Equus 3130. I didn't have a code reader that could read live data from my car and now that I have one, I really like it.

I've recorded some info while driving but I don't know how to interpret them or if its good or bad. If someone can help me with that. Also, what should be the "normal" value of each one.

The car: 2005 Cadillac CTS 3.6l VVT V6 Automatic transmission with 152k miles on it.
Fuel sys 1 : CL
Fuel sys 2: CL
Calc load(%): 49,8
ECT : 204F
STFT B1(%) -1,5
LTFT B1(%) 1,5
STFT B2(%) -1,5
LTFT B2(%) 8,5
Eng RPM 1680
Veh Speed mph 19
Spark Adv (deg) 33
MAF (lb/min) 3,505
TPS(%) 21.1
O2S B1 S2(V) 0,700
STFT B1 S2(%) NA
O2S B2 S2(V) 0.625
STFT B2 S2(%) NA
Command EVAP(%) 1.5
Fuel Level(%) 51.7
EVAP P(inH2O) 0.351
BARO(inHg) 29.5
O2S B1 S1(mA) -0.035
EQ Ratio 11 0.981
O2S B2 S1(mA) 0.054
Eq Ratio 21 1.016
CAT Te 11(F) 1111.4
CAT Te 21(F) 1117.0
ECU Volts 14.017
LOAD Value(%) 44.3
EQ Ratio 0.999
Rel TPS(%) 12.1
Ambient(F) 32
TPS B(%) 22.3
ACC Pedal D(%) 32.9
ACC Pedal E(%) 15.6
Command TAC(%) 16.4

Thanks a lot.

2005 Cadillac CTS
3.6l v6 vvt with 182k miles
OLM OCI (10k-15k miles)

#2084294 - 11/22/10 05:36 PM Re: interpreting scan data from obdII code reader [Re: Spykem4e]
Vikas Offline

Registered: 07/22/05
Posts: 10910
Loc: NorthEast
Wow, your car supports lots of parameters. Everything seems to be normal but you have only a single data point captured. I am assuming you are not having any engine related problems as all the data seems great.

- Vikas

#2084297 - 11/22/10 05:43 PM Re: interpreting scan data from obdII code reader [Re: Spykem4e]
eljefino Offline

Registered: 06/15/03
Posts: 30503
Loc: ME
Take the load calculation with a grain of salt. Usually idle is around 30-35% and we know that ain't right.

Decel in gear can get you much closer to zero. It's sort of an internal bias not related to actual flywheel HP.

I'm curious how accurate its fuel level is though compared to the gauge calibrated for idiots. (Temp gauges are too!)

#2084302 - 11/22/10 05:51 PM Re: interpreting scan data from obdII code reader [Re: Spykem4e]
Spykem4e Offline

Registered: 10/23/08
Posts: 385
Loc: Montreal, canada
Vikas, thanks a lot. The only problem I have with the car is a little rattle that I thought was pinging and that's why I bought the scantool to try to detect something. I could hear the rattle while I captured the frame so I don't know if its engine related or just a rattle somewhere in the engine bay. Can you help me a little about interpreting some data like STFT and LTFT that I don,t know what it is and whats normal or not. I know the basic like ECT temp, IAT Temp, load in % etc. But Eq Ratio, Spark ADV, STFT LTFT for example I don't know.

I was driving and the LTFT B2(%) always stuck at 8.5 while the other one was at 0 sometimes.

Eljefino: Thanks a lot. And to answer your question regarding the idiot guage on the cluster:

Fuel Level gauge was a little more than 1/2 versus the scan gauge 51.7% (The gauge is not accurate on my car. When its at 1/2 mark, I have about 1/3 gas left)

As for the Coolant Temp, its stuck at 1/2 mark on the cluster (but runs between 190 to 215 on the scan).

Edited by Spykem4e (11/22/10 05:54 PM)
2005 Cadillac CTS
3.6l v6 vvt with 182k miles
OLM OCI (10k-15k miles)

#2084319 - 11/22/10 06:06 PM Re: interpreting scan data from obdII code reader [Re: Spykem4e]
sunfire Offline

Registered: 04/08/08
Posts: 1574
Loc: Ca, US
My LTFT goes between 3-9, the average is around 6.
2005 Toyota Corolla LE | 65,000 | PYB 5W-30

#2084825 - 11/23/10 08:52 AM Re: interpreting scan data from obdII code reader [Re: Spykem4e]
Vikas Offline

Registered: 07/22/05
Posts: 10910
Loc: NorthEast
To see if the rattle is related to timing, you should monitor your timing advance, rpm, engine load only and collect many samples. If you notice that the rattle only happens at high ignition advance, then it *may* be pinging but more likely just a sympathetic vibration at specific rpm and load. My Maxima does that and I had mechanic listen to it and he assured me that it was not pinging. Pinging would have very peculiar "marbles in the coffee can" noise and will be pronounced.

You should capture more samples for analysis. Your fuel trims are good. The LTFT should be under 10 and yours are hovering close to zero which is great. One cylinder showed about 8 but you need monitor the trend. The number keep on changing all the time, so you need to get more information. LTFT is long term fuel trim. This is how ECM makes sure your engine is running most effectively. The manufacturer has fuel table map built in to ECM for RPM and load conditions. ECM uses data from O2 sensor to see if the car is running lean/perfect/rich and changes the fuel trim accordingly. There is lot more to it and you can read thesis after thesis if you google it.

And yes, your LTFT should NOT be stuck at 8.5%. If it is indeed stuck, then you might have slight leak in the intake plumbing for that cylinder. Generally speaking, you expect both cylinders LTFT to be about same and under 10% for a well running engine.

Your timing advance looks good. Generally It varies from 10 to 50. I do not know EQ ratio. It could be lambda which is 1 for stoichometric combustion (14.7:1) or it could be a coefficient to normalize your throttle position.

- Vikas

Edited by Vikas (11/23/10 08:54 AM)