ECM Code 55

[Funracer]

Runs great until 5000 RPM then terrible.

Manual says "System Lean Monitor"

Does this mean the O2 sensor is bad?

I did not see a diagnostics chart for this code in section 8.

91 with the usual mild mods, secondaries pulled, 37K miles.

I did a search for "Code 55" but the search engine says 55 is too common.

Thanks

[LGAFF]

Check fuel pressure, might have a bad pump or hose is off pump

[Funracer]

Going to reset and drive it again. If it happens again I will chk FP.

Thanks Lee

[tf95ZR1]

*

[93 ZR1 Barcelona]

Check Fuel Pump 2 fuse which is located on the auxiliary fuse panel. On the passenger footwell, remove the cover and look under and you will see a small panel with some fuses. One is marked FP2, check it.

If Fuel Pump 2 does not run, you don't have enough fuel on Full Power mode when the engine is WOT and this causes the lean problem.

[Hib Halverson]

Originally Posted by Funracer

Runs great until 5000 RPM then terrible.

Manual says "System Lean Monitor"

Does this mean the O2 sensor is bad?

I did not see a diagnostics chart for this code in section 8.

91 with the usual mild mods, secondaries pulled, 37K miles.

I did a search for "Code 55" but the search engine says 55 is too common.

Thanks

See pg. 6E3-A-81 in the 1991 Service Manual.

Generally, it means your engine is running out of fuel at WOT. Be careful with that and no secondary port throttles. You can burn pistons and valves in a heartbeat.

Either the fuel filter is restricted, the fuel lines are restricted or the secondary fuel pump is not working.

[Funracer]

Originally Posted by LGAFF

Check fuel pressure, might have a bad pump or hose is off pump

You called it Lee

[LGAFF]

We don't need no stinkin manuals