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Chasing codes P1395 P1396

8K views 7 replies 5 participants last post by  97OBS7.3L 
#1 ·
I've been tasked with fixing these error codes on my works 99' 7.3. I started by ohming out everything and found an open circuit on one glow plug and measured 0.5 ohm on the same uvch wire. I replaced the glow plug and the harness. Both codes came back after 3 cold starts.

I did some digging on the internet and they said either glow plug relay or shunt when both codes are present. I replaced the relay, to no avail, and then the shunt, both codes still coming back.

The truck starts great, drives great, no other codes or problems. I cleaned the battery terminals because they were a little dirty but no change.

All other glow plugs ohm out to 1.1 to 1.2. The new one is 0.9. Could they not be drawing the amperage message to keep the computer happy?

I'm at the point where I think either the engine harness is bad or the ECU is bad. Short of finding a donor vehicle to swap those two with, what else can I try?

Thanks.
 
#2 ·
Are the monitor wires connected to all three terminals with the shunt? They each have a section of (probably blue) fusible link in them, so that may be something to check also. A glow plug reading under 2.0 ohms is good, so that isn't likely the problem. Have you verified +12v to all of the GP pins in the valve cover harness connector? Checked the connectors for melted spots/burned pins inside and out?
 
#3 ·
Those all checked good. I ended up noticing that my multimeter had an amp draw setting and used that to discover that the 7 glowplugs that I didn't replace were below spec. They would start out drawing 15-16 amps but reduce down to 7 when hot. The new replacement tested at over 20amps at start and down to 12.5 at the hottest. Replaced the rest of the plugs and the codes didn't come back and now it's smoged and ready to go.

The plugs pulled out were Autolite plugs, stay away from them if you have glow plug monitors.
 
#7 ·
I replaced all 8 of my glow plugs, both UVCH's, and the Valve cover harness on each side when I had glow plug codes to get them to go away.

the harness is hard to truly diagnose and the relays are junk...

contact svt ford parts they have an incredible deal and took me maybe 4hours of work, no special tools or anything etc.
 
#8 ·
I replaced all 8 of my glow plugs, both UVCH's, and the Valve cover harness on each side when I had glow plug codes to get them to go away.

the harness is hard to truly diagnose and the relays are junk...

contact svt ford parts they have an incredible deal and took me maybe 4hours of work, no special tools or anything etc.
This where I'm currently at with harness. A breakout box would be nice at this point. Everything else checks out, however I need a meter that will test Amps. Waiting for my son to loan me his Fluke for that.

I'm chasing both codes as the OP was after some Motorcraft died, then those Autolites blew, returned and went with Napa Echlins. Installed new UVCH's and new GPR when I tried those Autolites.

I do wonder though if the Dealer reflashed my current reconditioned PCM to that TSB 98-15-1 many years ago. My original PCM was before it fried.
 
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