For once I wanted to make this a general any car post, but since it seems to come up a lot with tdci models...
We regularly see posts mentioning injector coding as a repair. What exactly is this?
My guess would be that with the high pressures used these days accelerating injector wear and the multiple injections of fuel into each cylinder per cycle, that the ecu can fiddle with the durations of injection and the intervals between them.
I can see that these parameters might be tweaked as injectors wear, or indeed to allow for variation in injector performance when new.
So, am I correct? If so what does recoding involve? Do they remove the injectors and test them to assess the flow rate accurately? Using the info gained to recalibrate the ecu?
Or am I totally mis-understanding?
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I thought it was simply that the ECU sometimes can lose the injector coding (after a reset or power failure), and needs to be reprogrammed with them.
I would suspect that main dealers would simply replace a suspect injector and program the new injector code into the ECU rather than test the old one ....
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AC
This is going to be a very dangerous question to answer without legal advice as the matter of "software correction factors" is just about to blow wide open.
What can be said is that the "coding" is a means of matching a grade of injector to the ECU to compensate for minute differences in manufacturing tolerances; for example, a Bosch injector could be rated as A to D with a A-grade requiring a few microseconds less to inject the same amount as a D-grade.
When the injectors are first installed; the ECU is told which grade is fitted and thus how much will be injected during each of the precisely-timed 12 micro-squirts per cycle. It has the matching mapping for the four types and, as all four will be the same grade, that's it sorted.
When it gets to TDCi injectors is the difficult bit, as they require far more software correction to function and it's a much more involved process as every injector has been found deficient in different modes in the post-built test - hence the 16-digit codes required to [try and] compensate and the difficulty of keeping such a mis-matched collection in the "zone."
I should say that this is a personal opinion and if the mods are unhappy with any part of it, feel free to delete it.
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Thanks Screwloose.
Thats pretty much what I thought it must be. Although as you say, you have to wonder about the quality of something that needs quite such a variation in parameters.
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also the injector coding is quite simple to carry out & plenty of diagnostic gear now has this facility. there are certain guidelines for different makes but the principle the same. If you suspect a coding issue a good Indy should be able to recode for you. Ford peugeot fiat renault Landrover ( L/R started off with 4 digit coding but how now got longer digits to allow for all variants ) etc all use this facility.
Doc
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