Injector 7 Circuit low, I have done some trouble shooting but I am at a standstill. Below is straight out of the ford service manual.
AB1 DIAGNOSTIC TROUBLE CODES (DTCs) 0261, 0264, 0267, 0270, 0273, 0276, 0279, 0282: CHECK FOR GROUND SHORT IN LOW SIDE CIRCUIT

DTCs below indicate a low side ground short in the circuit between the IDM and the injector. The following table lists the circuit to inspect while performing these pinpoint tests, based on the DTC retrieved during the KOEO On-Demand or Injector Electrical Self Tests.

Cyl. ---- DTC ---- Circuit
1 ------ 0261 ---- 555 (T)
2 ------ 0264 ---- 556 (W)
3 ------ 0267 ---- 557 (BR/Y)
4 ------ 0270 ---- 558 (BR/LB)
5 ------ 0273 ---- 559 (T/BK)
6 ------ 0276 ---- 560 (LG/O)
7 ------ 0279 ---- 561 (T/R)
8 ------ 0282 ---- 562 (LB)

Key off.

Disconnect injector valve cover connector at the suspect injector.

Measure resistance from the suspect circuit of the engine harness connector to battery negative post.

Is resistance greater than 10,000 ohms?

Yes: GO to «AB2».

No: GO to «AB4».

AB2 CHECK SHORT IN CIRCUIT TO GROUND

Install Rotunda Glow Plug Injector Adapter 014-00935 or equivalent to the valve cover gasket.

Measure resistance on the suspect circuit to battery ground.

Is the resistance greater than 10,000 ohms?

Yes: Fault may be intermittent, GO to «AB5».

No: GO to «AB3».

AB3 UNDER VALVE COVER SHORT

Remove valve cover and disconnect injector connector.

Inspect under valve cover (UVC) harness for shorting to ground.

Is fault indicated?

Yes: REPLACE UVC harness.

No: REPLACE injector.

AB4 CHECK FOR SHORT BETWEEN INJECTOR VALVE COVER CONNECTOR AND IDM

Key off.

Disconnect IDM.

At IDM harness connector, measure resistance from the respective injector circuit to all other circuits in the IDM harness connector and to chassis ground.

Is the resistance greater than 10,000 ohms?

Yes: REPLACE IDM. RERUN Scan Tool Diagnostic Test.

No: SERVICE short to ground between injector valve cover connector and IDM connector. RERUN Scan Tool Diagnostic Test.

AB5 CHECK FOR INTERMITTENT SHORT TO GROUND

Key off.

Disconnect IDM. Inspect for damaged or pushed-out pins.

All other connectors plugged in.

Using a DVOM and the flex tips supplied with the NGS Tester, measure resistance between the suspect injector low side circuit on the IDM connector to battery ground post. Refer to «injector illustration» at beginning of this pinpoint test for pin location.

Grasp the harness close to the suspect injector connector. Wiggle, shake harness while working towards the IDM.

Does resistance ever drop below 10,000 ohms?

Yes: ISOLATE short to ground and REPAIR. CLEAR DTC and RETEST.

No: IDM internal failure, REPLACE IDM.


so starting with AB1, i disconnected the external valve cover harness on the passenger side rear which has injectors 5 and 7, then I located the TAN and RED wire which was circuit 561 (Injector 7). using a multimeter I put one probe on that pin, and the other probe on negative terminal of battery. I didnt get any reading back…(good?). It says in the text to move to AB4 if you get a reading less then 10,000 Ohms. so I went to AB4 in the text above as stating. Here’s where I get a little confused. in AB4 it says “At IDM harness connector, measure resistance from the respective injector circuit to all other circuits in the IDM harness connector and to chassis ground.”. does this mean I need to measure resistance between circuit 561 and all other injector circuits in that connector(circuit 555, 556, 557, 558, 559, 560, 562)? If I put a probe of the multimeter in circuit 561 (TAN and RED wire) in the IDM harness connector and the other probe in any of the other injector circuits in the connector(555, 556, 557, etc…), i get nothing, and if i take a probe of my multimeter and put it to a ground on the chassis (as states in AB4) and put take the other probe and put it in any injector circuit on the IDM connector I also get nothing. What am i doing wrong? should I be getting any resistance when probing these? Am i doing everything right and I have a short to ground somewhere in the harness?

I have ohm’d out the valve cover external connector which comes back at 3.4 ohms (confirms UVCH is good), and to be honest the truck runs fine except when whacking it in neutral it sputters and blows white smoke. there is also a “IDM failure” code but I think that’s tied with P0279.

all I worried about is if I diagnosed the AB4 troubleshooting part right.

 

https://www.ford-trucks.com/forums/1...load-test.html

look at the ohm test in the link above and let us know where it fails on a reading

 

Alright this is what I came up with so far. After taking a look at the link I came up with the idea to Ohm out the injectors starting from the IDM connector. That will rule out the wiring from the IDM all the way to the injectors. Down below is a photo from a youtube video that explains how to ohm injectors from the connector.


by "bayou diesel" labeled "IDM Wire Harness Pin Test. P1316 DTC. 2001 7.3 Power stroke"



So to test the right bank, (cylinders 1, 3, 5, 7), you have to probe (with a multimeter set on Ohms), one probe in the Pin 24 (feed for the entire right bank, always stationary) and the other probe in pins 6, 21, 8 and 20 (injectors). I believe the spec is within 2.8-3.6, so im guessing if there is an open circuit (break in wire) in any of the pins then you would get no reading, and if there is a "low circuit" meaning the wire is still connected but there is a chafe in the wire, it would cause a high resistance reading? I could be wrong so if someone could chime in and correct me that would be great. Ill also check the IDM grounds but I doubt that's my low circuit problem In that link Knottyrope sent, I see someone talking about a place right above the driver side valve cover that is prone to chafe, but first things first, OHM out.

 

low ohm is a short
high ohm is open

if you probe those injector pins and get low ohms to ground, then it can be a chaffed wire in the loom as they are wrapped in a grounded shield to prevent crossfire and radio noises ( FCC RULES )

 

so one probe on an injector pin and other probe on negative battery terminal?

 

alright so here’s where im at. i pinned out all injectors, and they came back at 3.5 exactly. I also checked to make sure there was no short to ground through any injectors and to no suprise there wasn’t. i also had my leads on pin 24 (feed) and pin 20 (suspect injector), and with the leads on i shook every part and bent every part of the harness all the way up to the valve cover gasket connector. so I just ruled out that my UVCH is fine, my external valve cover connector is fine, and my external engine harness is fine. so it is led down to 1 point right? my IDM is trash? wouldn’t that make my truck run like sh**? also wouldn’t there be a code for every injector? I know someone down the street that has a idm but it would be off a 95 with an auto tranny (same as mine). are they interchangeable? lots of questions here.

 

IDM Electrolytic capacitors do fail over time and can run worse when hot

Try the IDM, any 94.5-2003 IDM will work on it

My IDM failed on me a few years ago. lost a bank like it was shorted.

 

ok that makes sense cause when i’m towing something and the truck runs a bit hotter, it has a harder “miss” so we will see what happens!!

Jack

 

update. for the hell of it i decided to do a buzz test and that code went away…. i just started the truck and noticed that its running a little smoother, so this is intermittent? weird…. truck was cold by the way.

 

possible break in the harness

maybe to the load test on it to find the break or undo the loom and pull each wire hard to see if any stretch out

could be a loose connector or the UVCH connector

 

wouldn’t my ohm amount change as I was wiggling the harness then?

also could the truck being cold (IDM cold) have anything to do with the buzz test coming out fine? I figure that you said the IDM could perform worse hot, and since it was cold it made the truck pass the buzz test...?

 

ohms will change, some meters are not fast enough to detect a break from wiggling. I prefer analog for this test but not many are around these days

IDM is a possibility, its not easy from here to decide it if it is

 

gotcha... I think im going to go try my buddies IDM, then if that doesn't fix my problem then I know for sure that my harness is the problem. Thank you for the help knotty!!

 

alrighty I think I have it pinpointed. Im almost certain it is my IDM. So I took the truck for a TIMID drive, no where above 2.5 grand and if i was i wasnt hammering on it. I got home with the truck warm, cut it, and ran the buzz test 3 times. no codes. Then I fired the truck up, and whacked it up to 2500 a couple times and the truck sputtered a little bit and white smoke came out the exhaust, and then when it came back down at idle there was a constant "haze" from the exhaust. So once again I ran the buzz test and got a "P1298" code which is IDM failure. I think its safe to say that my original, "truck sputtering and white smoke at 1700-2500 when hard revving" problem is my IDM all along. Also had a quick question which I might post another thread. I have forescan for collecting data and would like to know how accurate CCT is? the first time I ran it i got injectors 3, 5, and 6 that came back with "contribution/balance" fault or whatever, and then I ran the test again and got only 3 and 6 balance fault, then ran it again and got only 3....? one thing I can say is that I do hear a bit of a difference with the third injector when it gets cut... It doesnt run as harsh. every other injector makes the entire truck shake while number 3 still makes the truck shake but not as bad. thoughts?

 

2500 RPM cut out could be fuel or HPOP system but that code is also telling us something that the PCM is seeing.
Did you clean the PCM contacts and IDM?

What is fuel pressure?
Did you remove VC and check to see if oil is coming from base of injector? It should only come from the spout
this can cause a CCT issue whether or not the IDM is good/bad