# How to read CONSULT printout?



## SamX (Dec 2, 2003)

Hi guys,

I have a Consult printout after a routine servicing. There are a few terms which I don't understand, so I hope the experts here can help.   

MAS A/F SE-B1: 1.23v
HO2S1 (B1): 0.72V
HO2S1 MN TR(B1): RICH
A/F ALPHA-B1: 99%
B/FUEL SCHDL: 2.1 msec

Thank you very much :cheers:


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## se-r-57 (May 1, 2002)

SamX said:


> Hi guys,
> 
> I have a Consult printout after a routine servicing. There are a few terms which I don't understand, so I hope the experts here can help.
> 
> ...


MAS is the voltage the MAF is sending to the ECU
HO2S1 is the voltage the O2 sensor is reading the other HO2S1 is showing it's reading rich. For .72 volts thats right.
A/F alpha is the air fuel ratio and 99 percent is a good #
B/FUEL SCHDL is the injector pulse time in milliseconds. The time the injector is open.


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## SamX (Dec 2, 2003)

se-r-57 said:


> MAS is the voltage the MAF is sending to the ECU
> HO2S1 is the voltage the O2 sensor is reading the other HO2S1 is showing it's reading rich. For .72 volts thats right.
> A/F alpha is the air fuel ratio and 99 percent is a good #
> B/FUEL SCHDL is the injector pulse time in milliseconds. The time the injector is open.


Thanks for your answer. Just to clear up, what does MAS and MAF stands for? And you mentioned HO2S1 is the voltage the O2 sensor is reading. What is the importance of the voltage? If the air fuel ratio is 99%, what exactly does the 99% mean? Finally, what does the 'B-1' stands for?

Sorry for asking so many questions but I'm trying to learn more about the car. Many thanks once again :cheers: :cheers:


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## korner (Sep 23, 2015)

The B/FUEL SCHDL (Base Fuel Schedule)is the factory setting pulse width programmed into the ECU prior to any updating by the onboard run time correction determined 

by short term fuel trim(STFT) which then corrects Long Term Fuel Trim(LTFT) and the A/F ALPHA-B1 (The mean value of Air fuel ratio feedback correction factor per 

cycle) A/F ALPHA-B1 is based as a % with 100 being perfect. The B1 stands for Bank 1. 4 cylinder engines have only 1 bank. v8s have 2. Unfortunately Nissan doesn't define "cycle". It could mean drive cycle as per the emissions definition or 

it could mean 1 trip. It is sad that Nissan chooses to keep the value of B/FUEL SCHDL a secret, but the 2006 Nissan service manual for the Altima gives a clue. In the 

screen shot on EC-137 it gives 2.9 milliseconds as the midway point of good range. So that might be it or the screen might be a madeup one with meaningless figures. 

It seems that Nissan duplicated the Long Term Fuel Trim (LTFT) PID with one of their own called A/F ALPHA-B1. It seems to be almost exactly like the Long 

Term Fuel Trim. The computer updates the injector pulse width based on A/F ALPHA-B1 and NOT with LTFT. That would explain why the LTFT only shows up in the Nissan 

Consult tool when there is a DTC (diagnostic trouble code) . Nissan mechanics are taught to ignore what the LTFT says and to pay attention to the A/F ALPHA-B1. LTFT 

updates itself in 5 minutes of driving whereas A/F ALPHA-B1 is the mean value of the whole cycle whatever that is. Interestingly LTFT starts out as ZERO from the 

factory but as STFT gets large enough it changes the LTFT. LTFT is updated by B/FUEL SCHDL for each drive cycle and for each ECU RPM speed combo long term computer 

storage block. Nissan does not say how many different RPM LTFTs there are but I suspect that if LTFT is constant, long enough in each block then that LTFT number 

becomes the base LTFT from which the next major change is calculated from. LTFT number for each RPM speed combo is the only value that is kept in EEPROM long term 

storage. All other numbers are lost when engine shuts down. It may be that the computer uses only LTFT in the first couple of minutes until it goes into closed loop 

and then from then only A/F ALPHA-B1 is used to change B/FUEL SCHDL. To give an example my 2006 Altima had a faulty MAF (Mass Airflow sensor). I was getting readings 

of LTFT of +9 throughout most of the RPM range. That means the car thought it was running lean but really wasnt but the computer kept adding 9% fuel to correct the non 

real lean condition. I changed the sensor and almost immediately the LTFT went to -10 and the next day to -12.5 for most of the RPM cycle. What it really is doing now 

with a good MAF (and I wil prove or disprove this) is subtracting 12.5 from +9 which means that in reality it is only -3.5 from perfect and indeed after I decelerate 

to about 1000 RPM that is what my new LTFT is reading. Of course throughout all the rest of the RPM it is reading -12.5 However that is not 12.5% from the factory 

setting but is -12.5 from my previous LTFT of +9. So the car is actually running a little rich but only 3.5% rich. For a 10 year old car that is equivalent to 

perfect. I will prove this by getting the dealer to set all my LTFT to ZERO. I predict that the LTFT will relearn to the -3.5 number and NOT the -12.5 number for the 

whole range of RPM/speed blocks.


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## korner (Sep 23, 2015)

An update to the value of A/F ALPHA B-1. Another Consult 2 screen shot in the factory Service manual seems to suggest that the spec range is 87.% to 112.5 %. If that is so, then the safe window of operation without a DTC lean or rich code is 12.5% either + or -. That is half of what everybody on the internet is guessing that the car manufacturers have set for the rich or lean codes. Maybe other manufacturers use LTFT to set the codes but Nissan certainly doesn't. I have made an appointment on May 4, 2016 to have the Nissan dealer check my 2006 Altima with his Consult 2 machine and we will see if there is any correlation between LTFT and A/F ALPHA B-1. I suspect there isn't and thus the LTFT numbers are useless to tune by. In my previous post I said that LTFT was the only value that was stored in long term storage/memory. That is not correct It turns out that A/F ALPHA B-1 is also stored long term. This info comes right out of the May 2009 Nissan Petrol Engine Trouble Diagnosis manual that is printed by the Nissan Learning Academy that forces any Nissan mechanic not to divulge any information that is not in the Factory Service manual for each Nissan vehicle. Therefore the ECM never uses LTFT and I have no proof that LTFT is even stored long term. If it isn't then I would think that Nissan would be contravening the OBD2 standards. I would hope that LTFT is equivalent to A/F ALPHA B-1 and that both are stored long term.


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## korner (Sep 23, 2015)

Since then I have had a road test with the Nissan dealer mechanic sitting in the passenger seat with the Consult3 machine plugged into the OBD2 port. Us consumers cannot buy the Consult3 machines that are actually a dedicated laptop. Nissan won't sell them. The Consult3 shows a lot of computer PIDS (parameter ID computer diagnostic info) that a generic scan tool won't show. We can buy the old Consult2 machines but the price is $2000 for a used one on EBAY. You can't buy Consult2 brand new anymore. Anyway when I asked the mechanic to go to the screen that showed LTFT, the computer immediately set it to 0. In other words the programmers in Japan were told by head office not to let the Nissan mechanics diagnose with LTFT. They have to diagnose with AF/Alpha. The Nissan mechanic told me that AF/ Alpha is a combination of STFT and LTFT. After a year of looking at both STFT and LTFT, I have concluded that Nissan deliberately made them bogus. Because I cant afford a Consult machine I have no way of accessing AF/Alpha but using other parameters such as the O2 sensor info and the fact that I have replaced many components with brand new parts and knowing that I get 25 miles per US gallon I am convinced the car (2006 Altima 2.5 litre) is working perfectly. It has only 92000 km on it. However the LTFT keeps going up to + numbers and then it will go back down to lower positive numbers. Then it will repeat this scenario ad nauseum. This should not happen if nothing else is getting changed on the car.


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## Car guy (Mar 31, 2016)

Thanks for the updates, info.


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