1998 Ford F150 - 4.6L PCM Won't Reset

[joetngallagher]

This is a new one for me. It's a 1998 Ford F150 4.6. The service engine light not on with engine running. The bulb check is ok. All fuses are ok. The pcm will not complete the drive cycle test. At first I thought someone had just cleared the codes but the customer drove the truck for 7 days after bringing it to me and all readiness tests were not ready. I drove it for 4 more days and they are still not ready. I'm thinking pcm but i've never had this problem before. Have any of y'all had this happen?

[Tim Martin]

I have seen this already, especially on the Fords. What I did was go into Mode 6 and found the problem. Even though there was no codes, I have found Mode 6 very helpful at times.

[joetngallagher]

I thought mode 6 was just for reading sensor parameters and pass/fail status??? Is there something else I should look for in mode 6? Also in datastream all sensors appear to be reading within specs.

[Tim Martin]

I have seen where an evap test failed in mode 6 and that kept the evap readiness monitor from resetting. I had to bring the 2000 Ranger back and recheck the entire evap system very carefully till I found the issue. It turned out that there was a pending code also for an evap issue that had developed. I agree, some of the technology in these modern systems can be very challenging to relate to but it feels good to finally get it fixed.

I cannot say with any degree of certainty that in your case mode 6 will show you anything but I am simply sharing what has helped me in the recent past. I will be watching this post to see what is the cure for this perplexing situation for you. Good Luck!

[steven kiser]

how much fuel in it? the amount of fuel in the tank had a direct bearing on the monitors running.

[joetngallagher]

Fuel tank is 75% full. Mode 6 tells me that test id #41 component #11, test id #45 component #20 and test id #48 component #30 have failed. I do not know how to determine what these are without subscribing to the manufactures. Also ALL MONITORS ARE NOT RESETTING. This is what has me stumped

[Tim Martin]

Your fuel level is fine. The test numbers have to do with EVR, Delta, and O2 Sensor issues. These are common issues on these engines and their emissions systems. You need to do a rather thorough diagnosis on the EGR system and related components, including hoses, wiring, and switches. I have found Mitchell1 to be a rather good source for information on testing. Good Luck!

[steven kiser]

you may find the dpfe sensor melted and shorted. i remember ford having an issue with these and had to redesighn them. this year may or may not be in the effected time period. i do know that when they melted the internal wiring would melt together and on occasion stymie that side of the control.

[fortknoxx]

well, what did you come up with?

[Stewart Levy]

I seem to remember a note a bout a diode that corssion got to on the left fender inthe fuse block?

[steven kiser]

ya, me too. i was wondering what happened to that.

[brianp87]

hmm