Commanded And Actual Lambda Pid

Rod Diagnostician California Posted   Latest  

Is any one using the commanded and actual lambda P.I.D. for diagnostic purposes ,

and if so . how?

I like using it for confirmation of system integrity matching the air fuel ratio sensor milliamp “0” match in conjunction with fuel trims for proper performance verification.

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Spiro Service Manager
New York
Spiro
 

Rod, I also like looking at Lambda (very good PID). Another PID to help us decipher mixture status. I like to look at Fuel Trims while monitoring Lambda. It just so happens, today I used propane enrichment on a 2015 Ford Escape (2.0 L). Just for fun… Lambda dropped to 0.6, O2 Sensor Current went to -1.8 mA and Fuel Trims went to -30. it was cool to see Fuel Control (by ECM).

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Timothy Owner/Technician
Wisconsin
Timothy
 

Depends on the vehicle. Some OEMs don't offer the option for those PIDs, or will only give you the commanded PID. It is handy, to prove that actual fuel control is happening when the trims are saying the PCM is trying…

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Dan Educator
Washington
Dan
 

My experience is the “actual lambda” PID exists on the generic side, only on vehicles with wide band AFRs. It’s a good universal method for looking at wide band output.

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Agree
Michael Technician
Indiana
Michael
 

Dan, Many times when I'm not familiar with a car line(in my case any euro), or some component, I'm not knowledgeable of it's operation, going to generic helps me figure out how things function. In the old days, getting live data from Volkswagen, was a challenge, having to know the pid numbers. Also, converting crazy undocumented code numbers to generic Pxxxx codes. You do have to be…

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Timothy Owner/Technician
Wisconsin
Timothy
 

Especially as VAG vehicles don't have a true correlation when it comes to fuel trims, that matches their adaptions in enhanced…generic is almost useless when it comes to trim and such in the Euro world.

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Randy Diagnostician
Colorado
Randy
 

I assume you mean the generic EQ ratio PIDs? Why use the miliamps when the ratio number already tells you what the sensor is measuring? Maybe I am misunderstanding what you wrote. I mainly compare EQ Ratio to measured Lambda in order to find wideband sensors that drift out of calibration and do not set a DTC. diag​.​net/msg/m5bc029q63…

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Thanks
James Instructor
Quebec
James
 

Agree EQ ratio makes it simple, particularly when the wideband sensor is displayed in volts, who knows for each manufacturer what voltage lambda is.

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Timothy Owner/Technician
Wisconsin
Timothy
 

Never thought of that approach! I just learned the normal voltages for the makes that use them. But, things are changing, as far as the voltages are concerned, so this is a much better way to assess what ‘normal’ voltage is.

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Rudy Technician
Utah
Rudy
 

Whatever Randy said. Its probably more right than any other answer you'll get….

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Scott Manager
California
Scott
 

Hi Rod, In regards to generic PIDS, logging commanded EQ vs Actual EQ vs Fuel Trim on a road test is a quick way to validate fuel delivery. For E85 vehicles, I find it useful to take a look at commanded Air Fuel Ratio as well so one can tell what the ECM is inferencing for alcohol content.

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John Owner
New York
John
   

Scott, I am a bit perplexed by the MAP at 194kpa? Forced induction?

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Scott Manager
California
Scott
 

Hi John, Yes indeed, this is a turbocharged application. This is a 1.6L Mini (0.474 cyl air) and with the absolute load at 160% and cylinder air charge at 0.783 validate that the system is doing what it was designed to do!

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John Owner
New York
John
 

Scott, My question was merely throwing a line out to elicit a discussion. I use those pids quite often in checking VE and such. Nice representation of that in your graphs. Happy Holidays!

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