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P1276 Wideband 1 AFR Lean Trip

Understanding AFR

Discussion and questions related to the course Understand AFR

Page 1

Hi there, I have been working through a number of teething problems since getting my 1000HP XR6 turbo running with the new Haltech Plug & Play ECU.

One of the issues I am having at the moment is a P1276 Wideband 1 AFR Lean Trip.

This seems to occur at the upper RPM range as I'm attempting a gear shift at WOT. Is it possible for this lean trip to occur due to a fuel cut associated with a gear shift?

If this is a genuine lean trip due to a lean AFR what is the best way for me to start to pin point where in the tune this is occurring and how do I correct it?

What specifically should I log? I need to be careful replicating this as I don't want to do engine damage.

Thanks for your help.


I have spent some time going through logs and it would seem that the lean protection may be getting tripped above lambda 0.85 when Iam at WOT. The conditions set are 700ms, 50% throttle or more and xmanifold pressure.

from what I can tell Im seeing 0.86 /.87 lambda at WOT and its tripping it off. It doesn’t always happen though but obviously in some instances it lasts for more than 700ms.

should I be a little richer at these RPM/load levels?

Do I adjust the base fuel table or target lambda table?

Do I increase the lambda to say 0.88 in the level 3 protection conditions?


So first of all it's quite likely that the AFR being measured is lean during a shift, more so if the ECU is instigating a fuel or ignition cut for the shift. This isn't a safety concern though so you just need to adjust your safety parameters to give a wider margin or a longer time. Some ECUs will ignore the protection functions during a shift but I'm not aware this is possible in the Elite.

More concerning however is that if you're seeing 0.86/0.87 under WOT outside of a shift condition then this is quite lean and I'd definitely be richening this up. If you've got the VE table dialled in properly then you can make changes to the AFR by using the lambda target table.

Thanks for the help. Could you provide some advice to me on how I can confirm if the VE table is dialed in correctly? What are the basic steps I need to consider/confirm to ensure the VE table is correct?


This is really just a case of making sure that the AFR measured by the wideband is matching the targets in your AFR target table. This assumes that you've also correctly setup the ECU for the injectors fitted including injector flow and dead time values. Beyond this we're really just covering the basics of tuning the fuel/VE table here.