My truck decided to play F*O*R*D again today. I stopped at a 7-11 for a coffee, when I restarted the truck, it cranked about 20 times before stumbling to life, then running really bad and a solid *check engine* light.

I limped the piece of crap back home and pulled the codes. The 2 new ones were [KOEO and KOER] 22 ( MAP sensor out of range) and a 98 [KOER only] The weird issue w/ code 98 ( e4od 'hard fault present') is- my truck is a 5 speed manual and it has the correct ECU for the 5.8/5 speed swap I did last year. The MAP sensor was purchased brand new in April of this year so I dug out the receipt and took it back to the store. The lifetime warranty turns out to be a 'once-in-a-life-time' replacement but at least it got the truck back to running as good as it can, so my question is- any ideas on why it would show a code 98?

 

DTC 98 when displayed during the KOER tests indicates there is a Hard Fault present regardless of what transmission the vehicle has. Classic example why we always ask when the codes were displayed. They can have very different definitions.


From my buddy Al:

DTC 98 in KOER Hard fault present; "...Failure Mode Effects Management (FMEM) FMEM is an alternate system strategy in the PCM designed to maintain vehicle operation should one or more sensor inputs fail. When a sensor input is perceived to be out-of-limits by the PCM, an alternative strategy will be initiated. The PCM will substitute a fixed in-limit sensor value and will continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the PCM will return to the normal engine running strategy. Engine Running DTC 98 or 998 will be displayed when FMEM is in effect. The Malfunction Indicator Lamp (MIL)/Message will remain on when FMEM is in effect. The MIL will come on while the engine is operating in Failure Mode Effects Management (FMEM) or Hardware Limited Operation Strategy (HLOS) modes. The light will stay on for at least 10 seconds, then stay on as long as the fault causing it is present. If the MIL flashes quickly (less than 10 seconds), the MIL circuit should be checked for concerns. Refer to «Quick Test». In FMEM mode, the PCM is receiving a sensor signal that is outside the limits set by the calibration strategy. In this mode, the PCM uses an alternate engine control strategy to maintain reasonable vehicle operation in spite of the fault. The DTC associated with this fault is stored in Keep Alive Memory (KAM). If the fault is no longer present, the light will turn off and the vehicle will return to the normal vehicle strategy. The DTC stored when the light was on is kept in Continuous Memory for the next 80 warm-up cycles (40 cycles on some applications) and then erased.

 

Thanks for the insite. It's interesting to know that there is a 'limp mode' built into the programming of the ECU.

The truck seems to be running like it used to after replacing the part, so I'll just keep my fingers crossed that this pig won't leave me stranded again.......