On my 2003 Excursion with the 6.8 V10 I have been having problems with it dieing at stop. I has been running rough, so I had the codes pulled and the P0720 was the only code showing. So I cleaned the speed sensor at the rear differential and the miss got a little worse. Next I changed the sensor and it still did not prevent it from dieing. I borrowed an OBDII scanner and P0420 is the only code. I freeze framed it and this is what I got. The test was done with the key on, engine off after it had died.

Fuel sys 1 - OL
ETC - 143 degrees
STFT B1% - 28.9
STFT B2% - 28.9
IAC - 105 degrees
MAF - .021 lb/min
TPS - 20%
STFT B1 S1% - 28.9

Does this mean anything? Someone told me that the MAF reading did not look right. Others have mentioned a bad coil. I have a new plug coming for the Speed sensor. I would like to know what to look at next.

 

O.k. guys I think I fixed my problem. I was thinking about my MAF sensor and I decided to try and clean it, I only had some Electrical contact cleaner so I used that to spray on the MAF. I put it all back together and immediatly I noticed the miss was gone. I took it for a short drive and after several stops at idle and no miss or dieing. Lets hope it was that simple. I will post back after a few days of driving.

 

Drive it for a week before declaring it's fixed. P0420/430 faults usually require at least two drive cycles in which the test runs and fails to set.

 

I am sorry guys I titled the thread wrong. The code is P0720 not P0420. I am sorry for the confusion. Can someone change the title to this thread?
I still notice a very slight miss occasionally. Last night it did die on me twice but straightened up and did fine going home. I also think I have a slight leak in one of my fuel lines. I was going to checked my fuel filter and I noticed the line attached to the filter bracket was rusty and was damp with gas. There may be a loss of fuel pressure also with this leak.

 

[QUOTE=Paul T;
" so I had the codes pulled and the P0720 was the only code showing. So I cleaned the speed sensor at the rear differential and the miss got a little worse "
.................................................. .....................
(This is where I made an embarrassing mistake not long ago )
.................................................. ............
VSS-SpeedSensor -Location (on top of differential)

Output Speed sensor (location on top of tranny).
.................................................. .........................
P0720 means the output speed sensor isn't being seen by the PCM. It might be the sensor, or it could be the wiring between the computer and the sensor. It doesn't automatically mean replace the sensor. (error code p0720) .
........................................
Check to see if these (locations of 2 distinctive sensors) are applicable to your vehicle.
Hoping this might help you . Good luck.

 

I found the sensor you are talking about on the transmission. I checked the wiring and it all seems to be o.k., I also unplugged it and checked for dirt then plugged it back in. Other than change it out I don't know what to look for. There is an obvious miss that is not setting any codes other than P0720. Does anyone know what the MAF sensor reading should be? Mine MAF is .021. Any other ideas?

 

The data you posted isn't of any use. Reset the PCM KAM and run it until it codes again. Then, record the complete freeze frame data.

 

if it's jerking, dying at idle, running rough it can also be a ground fault (i was getting a flashing OD light as well). i went through some of the same trouble shooting code P0720, replaced OSS ($20 part) didn't fix it, had the alternator rebuilt by a local starter guy (awesome rebuild man $60) cause read about a diode that could go out in the alternator....... still had a shudder/rough idle/cutting out

last but not least.... i did a plug change with COP boots and springs!

couple of the COP boots had some cracks in them...... fixed the issue. the COP arcing and causing a ground fault, every time the plug would arc it sent a ground signal to the torque converter to lock up. since the converter lock up works off a ground signal that was throwing a P0720 code.

 

Thanks Jason, I think I will do a plug boot & spring change. I will let you know what happens.

 

Update: I changed the plugs, boots, & springs tonight and took it for a 3 mile drive to my Mother-in-laws. X was running great until I got there and put it in reverse and it died. Restarted and put it in reverse again and it died. Finally got turned around and let it idle. There was a slight miss but no CES light. Put it in drive and went about 50 yards and stopped and it died. his time the CES light came on and stayed. Restarted it and drove home and put it in reverse and it died. Finally got it parked and shut it off. I am going to check the grounds tomorrow. I had the codes checked today and p0720 & p0722 came up. I had changed the OSS and it did not help. I ask if there was any cylinders missing and he said no. Something was causing it to stumble though. The truck seems to die only in gear. I found my fuel pressure tester but I need an adapter for a Ford. Fuel pump was changed last fall and fuel filter last week.

 

You should check the wiring to the OSS. That's the sensor on the top, rear of the transmission. Looking at the wiring doesn't do anything useful. You need a meter and the knowledge to do a complete electrical check. If you don't know how it may be a good investment to pay a pro to check it for you.

 

What should the reading be at the plug? Would a bad ground cause this? I admit I have very limited knowledge with a meter. I checked with the local Ford dealer and they wanted $85 to put it on their computer. Right now money is tight due to a customer not paying and others taking 45 to 60 days to pay. I am going to check and clean all the grounds I can find today and see what happens. I really need to get this thing running again.

 

You need a professional.

I don't recommend a dealer for this. A good independent shop would be much more likely to have the knowledge to find a fix a wiring issue such as this. Putting the truck on the computer won't find the problem. I guarantee that.

 

Thanks, Mark for the advice. I checked the fuel pressure today and with the key on no start it pressurized up to 36psi. After I started it, it went to 32psi and held. I am leaning toward a bad COP. I am still only getting the P0720 code. I checked and cleaned all the grounds yesterday.

 

You have to verify circuit integrity and move on from there. A good tech with a scope should be able to narrow it down pretty efficiently. Keep us all posted.