I am sure there is a way to tell in an HX with a volt meter.
Or if you have a scan guage ii, do this: (I got this info from brucepick)
XGauge procedure can be set up to be a LeanBurn indicator:
Use the code below to monitor lean burn with the scan gauge II
To Monitor Lean Burn, type in:
TXD 686AF10115
RXF 044105150000
RXD 2808
MTH 000100020000
NAM LBN
When it reads zero you're in LB.
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