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Discussion Starter · #1 ·
I recently bought a consult cable and downloaded the ecutalk software on the lap top and it works fine with all the info at my finger tips, but my question is where can I find out info regarding sensor parameters, what voltage at what revs they should read and get a better understanding of it all. Tb42e
 

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Heres a copy and past i had saved as i have ecu talk for our Z32 its a great little tool for checking the health of the engine management

"ECUtalk values

Note - Expected values: are just rough guides, they arent the be all and end all (and some people may disagree with what ive put down, if you do just post and put forward what you're experiences are or what the service manual etc says, as i havent referred to any). Any other omissions or corrections also feel free to post.

Speed, RPM - if you dont know what these are...*

Fuel Used, Distance, LPH (litres per hour) - should be self explanatory, these are from the trip meter screen on ecutalk display, and are recorded for the current trip (since car was started). All trip meter sensors will only be accurate if you set your number of cylinders and injector size in the options (and even then may be off slightly if your injectors dont flow rated amount or due to sensor inaccuracies - e.g. speed sensor is generally slow to react)

Voltage - the voltage the ECU is being supplied with.*
Expected values: around 12V when car isnt running, 14v when its running

Economy L/100KM/MPG - economy reading (ecutalk has instant and trip readings), instant - how many litres used per 100KM if you kept driving at current speed/load, and trip is what has actually been recorded for current trip.*
Expected values: trip obviously depends on the trip, instant value depends on your car and how you're driving, but typical cruising values should be under around 20L/100KM, higher than this is normal typical of high load. it should read 99.9 (i.e. infinite) when you arent travelling anywhere, since you are using fuel but the car isnt moving.

Injector %: The duty cycle, or percentage of time the injectors are open for. If this hits 100% then it means the injectors are open continuously. This isnt necessarily dangerous if you're running really rich AFR (air fuel ratios), because you'd need to make a bit more power past the 100% mark before you lean it out to a dangerous AFR. still worth dyno checking etc if you're hitting 100% a lot.*
Expected values: At idle this should sit at 1-3%, above this should roughly correspond to how much load the car is under, normally cruising/light loads you wont get much above 20%. Note: some cars may have 2 'banks' of injectors.

Timing (degress BTDC): how many degrees (of a circle, rather than temperature ) before the cylinder reaches TDC (top dead centre, maximum compression) that the spark plugs ignite the mixture. Some peoples first thought might be wouldn't you just ignite at the top? the reason you need to ignite before the top is because combustion takes time to propagate through the cylinder, so you want to give ignition a bit of a head start so maximum pressure occurs at the start of the down stroke.*
Expected values: generally the values should be > 0 (i,e, BTDC rather than after TDC, ATDC). this can be quite low at cold start up maybe jumping around like 3-10 degrees depending on car. Generally timing increases with RPM (at same load) and decreases with load (at same RPM).

AAC: Auxilliary Air Control, is what allows air into the engine bypassing the throttle (otherwise the car would stall when you take foot off throttle if it was the only way for air to get in), in addition to the air allowed in via setting of idle screw (i dont know if that air goes in via same valve or what). basically this valve is controlled by the ECU and can open to raise idle (e.g. when aircon is on), often will be used to 'catch' a fast dropping RPM so you dont stall, etc.*
Expected values: when the car is warm and at idle, this shouldnt read higher than around 15-25, any higher indicates that this valve is making up for an incorrectly adjusted idle screw (i.e it has to compensate by being continually open more, this is bad because it means it has less room to move, e.g. to 'catch' falling RPM, etc). I personally had warm idle AAC value up at 50-60 once, and this resulted in the car stalling when being started when it was warm (AAC couldnt catch the falling revs after start motor stops).

O2 Sensor: oxygen sensor, measures whether the mixture of exhaust gases is either 'too rich' or 'too lean'. it doesnt really measure the AFR itself, because its narrowband sensor, and as such is more just a switch saying one way or the other, and the ECU uses it like this - when the car is under light load/cruising/etc conditions, it will continually adjust the fuel so as to hover around the 14.7:1 stoich mixture (or whatever the ECU/o2 sensor combination is targetting) ratio.*
Expected values: when the car has warmed up, and is cruising along at light load, this should be swinging back and forth from 0.1v to 0.9v or there abouts. if the sensor remains at 0v or 0.3v (or fixed at any other value, these are just most common), then it is dead. Note: some cars may have 2 x O2 sensors.

Temperature - the coolant temperature of the car.*
Expected values: up around 80-95C (depending on car and fan turn on/off values) once warm. You dont want this too low (e.g. if thermostat stuck open) as the car doesnt run efficiently when cold.

AFM - air flow meter: sensor that measures how much air is coming into the engine, which is generally synonymous with 'load' on the engine. this isnt necessarily linear measurement.*
Expected values: i think this reads about 0.3v? when the engine is off, a bit over 1v when engine is idling, and up to 5.1v (full measurable load of AFM, but you still may draw more air past this point, which may lead to fueling/mixture problems? some (all?) cars may have fuel/ignition cuts once the AFM maxes out? Note: some cars may have 2 x AFMs

TPS - throttle position sensor. measures how much the throttle is open. ECU uses this to know when load is changing i think because it does some fine tuning differences with fuelling depending on if you suddenly step on accelerator etc? used in conjunction with other sensors to calculate fuel load and used by auto transmision computer
Expected values: around 0.4v when closed, around 4v when fully open."
 

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Discussion Starter · #4 ·
Wow thanks for the info anti, this has help a lot also thanks for the detailed response made my understanding a lot easier
 

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AAC: Auxilliary Air Control, is what allows air into the engine bypassing the throttle (otherwise the car would stall when you take foot off throttle if it was the only way for air to get in), in addition to the air allowed in via setting of idle screw (i dont know if that air goes in via same valve or what). basically this valve is controlled by the ECU and can open to raise idle (e.g. when aircon is on), often will be used to 'catch' a fast dropping RPM so you dont stall, etc.*
Expected values: when the car is warm and at idle, this shouldnt read higher than around 15-25, any higher indicates that this valve is making up for an incorrectly adjusted idle screw (i.e it has to compensate by being continually open more, this is bad because it means it has less room to move, e.g. to 'catch' falling RPM, etc). I personally had warm idle AAC value up at 50-60 once, and this resulted in the car stalling when being started when it was warm (AAC couldnt catch the falling revs after start motor stops)."
Just wondering if I have a figure of 80 is it a sign that the AAC is broken ?
 
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