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Scott W.
Scott W., Ford Technician
Category: Ford
Satisfied Customers: 3312
Experience:  28 yrs. experience as Ford ASE Master Technician. Accolades include being a 2005 Ford PTS Regional Finalist and 2006 ASE Ford National Technician.
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Excursion: Ron P0135 & P0155. 2000 ford excursion 6.

Customer Question

Hi Ron
P0135 & P0155. 2000 ford excursion 6.8.
Submitted: 1 year ago.
Category: Ford
Expert:  Scott W. replied 1 year ago.
Hello my name is Scott
Expert:  Scott W. replied 1 year ago.
Has the PCM been reprogrammed?
Customer: replied 1 year ago.
Not since I have replaced the O2s. I purchased the truck a little over a year ago and I don't know much on the history.
Expert:  Scott W. replied 1 year ago.
There is a TSB to have the computer reprogrammed for these codes.
Customer: replied 1 year ago.
That figures. Guess I'm going to have to go to the stealership after all.
Expert:  Scott W. replied 1 year ago.
Hopefully this is the fix since you have tested everything else, we have replaced a few PCM's for this also. I would try a reprogram definately first though.
Customer: replied 1 year ago.
I have been looking for weeks for any TSB or recall information on this problem and couldn't find anything. I am a certified diesel tech with 20 years including 7 years on forklifts and this has been driving me crazy.
Expert:  Scott W. replied 1 year ago.
Ok, let me look and see I can find it for sure.
Expert:  Scott W. replied 1 year ago.
Ok found it, it only says for 5.4 engines that this tsb applies. Since yours is a 6.8, I would still try the reprogram, if this doesn't fix it and you have checked powers and grounds to the heater circuits, it only leaves left the PCM. You might try monitoring the power source to the heater while driving to see if you are losing power while driving like a chafing circuit. Otherwise I believe you are looking at a PCM, you could try Ford for a PCM but everytime we try, they are obselete and we get then from either NAPA or CarQwest.
Customer: replied 1 year ago.
VIN 1FMNU41S5YEB53923. in case you need it.
Customer: replied 1 year ago.
If the ground coming from the PCM is grounding out somewhere it would show ground at the plug but would it still give a code?
Customer: replied 1 year ago.
Are both O2 grounds on the same circuit or do they have a common ground?
Customer: replied 1 year ago.
Ment to say separate circuit
Expert:  Scott W. replied 1 year ago.
Ok the power supply is for both, I will get you a diagram in a minute, the grounds to control are separate. When the computer sees the no voltage on the ground side of the circuit, not commanding it on, it will still set a circuit fault since it knows it should see 12 volts here not commanded, and then go to 0 volts when commanded on.
Expert:  Scott W. replied 1 year ago.
Here is the diagram.
Expert:  Scott W. replied 1 year ago.
Since they are both setting at the same time, I suspect you may have a power supply that is intermittent.
Expert:  Scott W. replied 1 year ago.
If there is no interuption in the power supply while driving using a DVOM, and the codes reset, then I would try a PCM.
Customer: replied 1 year ago.
Per the diagram if I was losing power far enough back in the harness to affect both O2s wouldn't I get an EGR code also? Sorry about all the questions I don't believe in throwing parts at a problem.
Expert:  Scott W. replied 1 year ago.
No that is a good point, it could also set egr circuit code if the power was lost also. I would try the reprogram first since a known concern with the 5.4's is out there, if it doesn't fix it, I would replace the PCM.
Expert:  Scott W. replied 1 year ago.
You might try checking that splice also in the harness, it is a long shot, but might be worth looking at too.
Customer: replied 1 year ago.
I will see if I can get a cost for reprogramming and if it's not too much I will try that first. I have inspected as much of the harness I can with out pulling parts off or removing the wire loom.
Expert:  Scott W. replied 1 year ago.
Ok thats what I would do first.
Customer: replied 1 year ago.
PCM has been checked and has the newest update.installed new OEM O2 sensors. Found the CHT sensor and the ECT sensor resistance was off by a few ohms. installed new CHT & ECT sensors. If this doesn't work I don't know what else to do besides replace the PCM. Can you get a drawing of the O2 pin locations on the PCM?
Expert:  Scott W. replied 1 year ago.
Here is PCM connector
Customer: replied 1 year ago.
Where is the location for the O2 grounds
Expert:  Scott W. replied 1 year ago.
The grounds go through the PCM
Customer: replied 1 year ago.
I know they go through the pcm. What are the pin locations
Expert:  Scott W. replied 1 year ago.
You have the link in a previous post up on may 18
Expert:  Scott W. replied 1 year ago.
Run this pinpoint test.