Will my '98 Expedition (EB, 4WD, 5.4L)still run if the Electronic Control Unit has failed? I had the check engine light come on and the OBDreader pointed to the mass air flow sensor, which I replaced. The truck continued to miss, so I took it to the shop. The mechanic told me the ECU and all 4 O2 sensors were bad. Its hard for me to believe all those failed at the same time, so I've taken the truck back home and will, if necessary, buy a new ECU from an after-market shop and do the repairs myself. Also, any tips from anyone that will help me when I change out the unit and the oxygen sensors? Thanks.

 

I'd start over and read/post the DTC's here.. Chances the ECU/PCM failing along with the MAF, and all the 02's would be very slim..Very.. Doen't mean there isn't a component or circuit failure..

 

Thanks, Hayapower - I'll do that scan and have the codes posted hopefully sometime tonight. I need to get the truck back to normal soon, but don't need to break the vacation budget to do it!! Thanks again.

 

I went to have the DTC's read this morning, and there were none stored in the PCM. The "check engine" light is off, no other warning lamps are on, all gauges read normal, and the truck is idling really, really rough. It would hardly move forward until it had run for about 3 or 4 minutes. It runs semi-ok at road speed, but can still feel some surges. The tech reading the handheld said if the PCM was bad, the handheld would have indicated such. He believes the computer and the O2 sensors are all ok, and the miss is caused by something else. Your thoughts? I have a shop in town that I trust, so will likely have the truck over at his place on Monday to look into the problem.