Hi guys, I have a problem with the IPR wiring...I unplug the pigtail from the ipr valve and I get 12 volts on red wire and .02 volts on yellow/red wire showing ground... When I plug it back in the red wire turns into a ground and does not supply voltage to IPR valve thus creating a crank/no start. When I supply 12 volts direct to the IPR , motor starts and runs. Also , when I test for 12 volts on red wire with my voltmeter, get battery power, but if I try with a test light it shows no power... Not enough to light up the test light. When I test yellow/red wire for ground with a test light, it comes on very dim. I don't know what would cause the circuit to show battery power with a dvom but not enough power to light a light bulb in a tester. I tested ohms from the 12 way plug to pigtail-5.7 ohms
IPR 5.7 ohms IPR is new
Pigtail to PCM ohms 5.7
12 way connection to PCM connection is 5.7 ohms thus completing the circuit.
I don't know what would cause the circuit to go from battery power down to 0 volts when everything is connected and there is a draw. Sometimes it will rest at 3 volts too. Could it be a bad relay? How to check and location? Bad PCM? Shorted harness? Any advice is appreciated.

 

Sorry, I forgot to tell you what I have... 2006 f250 6.0l xl 4x4

 

Any body?
Any suggestions?
Is it normal that the pin on the pcm shows to be a ground pin?

 

Well...I guess the best I can do is give you the story on how I got to this point...maybe someone can help...February, I get a code for turbo underboost and check engine light, 3 days later a crank/no start. Because I wanted to do the stc, standpipes, plugs, blue spring fuel pressure upgrade, oil cooler, egr block off in the summer, I did it when it actually quit...in the middle of february...outside in the cold. Just to be thorough I threw in a new ipr and icp. Got everything back together and got a crank/no start. Waited for my AE to come in and it showed low high pressure oil. Did a leak test and attempted to close ipr with the software. Now, the software showed that I shut it down but I heard air leaking. Pulled valve cover and heard air leaking. Pulled new plugs, all good. Cranked engine looking for oil leaks from rail to top of injectors, nothing. I found it odd that I did not hear a change in the air leak when the ipr was commanded off by AE...so I thought that the new ipr was damaged, maybe I did not clean the engine good enough. I pulled the new ipr, found the screen with a bit of orange felt on it...must be the new filter...cleaned it...bench tested it...re installed it...put 12 volts direct through a separate pigtail and performed the leak test...no leaks...either valve cover or oil filter housing. The ipr is working but not from the harness of the engine. I cranked the engine putting 12 volts direct to ipr and it fired. I shut it down within 3 seconds. I tested the truck's pigtail...the red wire has battery power...the yellow/red show to be a ground. Once I connect to the ipr, both wires show as ground....ipr wont work without power...no oil pressure...no start. So, this leads me to believe that there is a short in this circuit somewhere...but when I check with ohms, seems to check out good...unless I'm doing it wrong. Sorry for the novel, just frustrated. Any ideas, advice would be appreciated. Electrical is not my strong point. Thanks in advance.

 

isolate each wire then load thest the circuit with a high beam blub as the load. make sure pcm is disconnected, do not back probe to do this. iwiggle test the harness while doing this. if the harness proves out suspect possible ipr or pcm.. but if you can 12v it and it starts really you may be down to a pcm.. however......
I have seen a number of failed harness with this basic concern Ive been lucky enugh to fix them all with connectors for the ipr. when doing the repair cut thye ipr harness as far back as the new connector will allow without being streached.
the next way to test this is to over lay the harness.
also thinking about it I had one that had a purned pin at the square connector on the drives side fender. pulled pins from connector and bypassed hard shell was a fix for that one

 

Thank you Cheezit, you gave me more ideas. I will try these things tomorrow. I don't know if that pin in the PCM should be a ground or a 5 volt ref to control IPR? I would run a separate wire to and from the IPR to pcm but I think the 12volts are shared with the fan, egr and gpcm... Don't want to screw with those circuits too. This is tough! Thanks again.

 

Have you tried a continuity test between the 2 wires with the IPR disconnected and checking from the PCM end of the harness?

 

As I mentioned, not good at electrical...so I could be doing it wrong... That being said, I checked ohms from IPR connection to PCM plug - IPR unplugged, PCM unplugged, so yellow/red wire isolated, and I got around 5.7 ohms.
Also checked from IPR plug to 12 way plug on driver fender, red wire isolated, both unplugged and got around 5.7 ohms too
Then I checked ohms going through the new IPR - 5.8-6 ohms
Then plugged in IPR and checked from 12 way plug to PCM plug- 5.8 ohms
I think that means there is minimal resistance in the line.
Then I tried plugging in 12 way plug, key on, PCM unplugged, I get 12.7 volts- battery power in the red line.
Then when I complete the circuit and plug in PCM , I lose batt power in red line and everything goes to 0 volts
Then I tried to plug in 12 way- unplug IPR so I have my 12 volts at the end of the connector or at least that is what it shows on my dvom, but if I put a test light there, the light doesn't show power
Then, I put my power probe , learning how to use it still, on the connector and it show battery voltage in the red line. Great, I've got power, so then I connect my test light to the power probe that is connected to the red line at the IPR connection and it changed instantly from battery power to ground beeping like crazy from ground to power alternating quickly back and forth. It is like it collapses when it senses a load on the circuit. Wish I was better at this.

 

No Worries Bud your doing Great at this


Have you Ohmed the Wire Harness Clear to the PCM Plug


Are you testing for power with the Key On??

Theres no powwer with the key OFF

 

Hi blade35, thanks for taking interest. I believe I have ohmed the wire from the 12 way plug, red wire, all the way through the IPR where the the return line turns to yellow/ red and runs back to the middle connector of the PCM. I got approx 5.8 ohms. I did that by unplugging 12 way and PCM and put one end of the dvom on the red wire pin and the other end of the dvom on the PCM pin where the yellow/red wire ends. 5.8 ohms on display. Hopefully I did that right?

I tested for volts with key on. Now with the IPR pigtail unplugged, I get battery power in red wire, the other wire shows as ground. As soon as I plug in, I lose my 12 volts. That's why I'm thinking maybe a short? But why would
Ohms be okay?
Drove me nuts. I thought all the work I did was no good. I've been cranking this truck so much that I know I'll need a starter after this. Then I figured if the IPR is not getting power, it can't close and build high pressure. I connected 12 volts direct to the IPR and the truck fired for the first time since February. I shut it down after a few seconds because I know the IPR can't take a full 12 volts for long.
I think I'm going to follow cheezits advice and load test each line with a headlight... See what happens.
Would a bad relay fail when a load is put on the circuit but show power without a load? Idk?
Wiring harness short? Or as Cheezit said, PCM
I don't understand when he said "overlay the harness" should have asked him.
I will see if there is power without the key on.

 

In lay men's terms (overlay the harness) running a new wire from one connector to the other connector and splicing at the plugs. This eliminates the bad wire and saving the cost of the part and a lot of labor.

 

I would begin to suspect a defective sensor since your circuitry seems to check ok but goes to pot when plogged into the sensor. Try a known good sensor as a quick test.

 

first off of he can hot wire the ipr and have a running as was stated truck odds are good its not the ipr.
next ohm meters have there place, you used it correctly, it failed to identify your concern, move on to load testing.
I will say even after I was all done and load testing passed I would try a new connector over a new pcm, they do fail but not very often

 

It should be noted if not already clear that the signal going to the IPR is pulsed at a duty cycle and not a constant voltage. Most Multimeters will not properly register the oscillation of the signal.

In other words you can't just test the signal/power at the connector with a multimeter.

I'm gonna agree with everyone in that replacing the connector is a good idea.

 

this is why i suggested load testing an isolated circuit as the correct method of testing