Code 55, Fuel Lean Monitor: Notes

PCM is capable of determining if fuel system can deliver adequate fuel during power enrichment (heavy acceleration). During power enrichment conditions, PCM expects to see both O2 sensors registering rich. If both sensors do not register rich, Code 55 will set.

NOTE: Test numbers refer to numbers on diagnostic chart.

Code 55 will set if PCM detects lean O2 sensor voltage for 8 seconds during power enrichment. This checks for proper fuel pressure.
Restricting the fuel line allows fuel pressure to build to greater than regulated pressure (greater than 47 psi). DO NOT allow pressure to exceed 60 psi.