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Solved by OP.
Further information on testing from Fixya Master Expert Larry Ng.
K Berns Sep 12, 2013
Well the problem ended up being the Ignition Switch.
Thank you everyone for your help.
Larry Ng Jul 22, 2023
bingo that, PICKUP TRUCK?>>>????????
no the ECM is not shot, the power feeds are bad.
a super simple problem in the hands of a person with DMM
K1500 4wd
1996
ok here is the wiring
Run FEEd ignition switch out.(or in)
those 2 fuses are dead key off that is a fact
seen in the service manual. schematics
20amps and not blown
the hot side is hot only key on
that means the key switch is dead. if battery good.
it cranks so power to the ignition switch is good and battery
so the ignition switch is blown out.
easy diagnosis.
is the IP cluster dead., yes, ignition switch is bad
the IGN switch sends power to cluster and engine controls
Check fuel pressure. Have you replaced the fuel filter on schedule? Verify that the fuel pump is getting power. Power goes through an in-line fuse, then the fuel pump relay or the oil pressure sensor. (The relay bypasses the oil pressure sensor while the engine starts, but fuel pump power goes through the sensor during normal run operation. If you lose oil pressure, the fuel pump is shut off to protect the engine.) On four-cylinder models, the fuse is in the fuse block (E PUMP 10) The fuel injectors are connected to the ECM fuse on one side and straight to the engine computer on the other side. Check the connectors and wiring, especially at the injector.
There is a fuse that deals with the fuel pump circuit through the ECM. If you haven't checked it's in the fuse panel under the hood in the engine compartment on the drivers side by the brake master cylinder. I hope that you have a cover for it with the names of the fuses. The fuse you want to check will be the fuse marked "ECM B". I gave you a picture of the fuse layout but it's not a good one but I did put an arrow to the one I think it is. I pretty sure that's the one but not 100 percent because it's pretty blurry. In any case there is a fuse marked "ECM B". I would check there if you haven't already. Other than that You may have to check your wiring. There is a fuseable link at the starter you may want to check if that fuse isn't blown. I hope this helps and good luck.
The fuel pump relay is powered by a fusible link connected to the starter solenoid on the positive battery terminal. That fusible link feeds the 10 amp fuse near the relay. You can test the fusible links with a 12 volt test lamp. If the fusible link test okay check for an open circuit in the wire between the link and the 10 amp fuse. Hope this gets you fixed.
Check for 12 volts power at the fuel pump harness. If no power is going to the pump, check the fuel pump relay. Also, check the fuel pump inertia switch. Ford usually has it on either inside left or right rear trunk fenders.
ECM B fuse supplies a constant 12v hot at all times to the VCM/PCM and to the fuel pump relay. The fuse is blowing telling you that there is a short to ground somewhere. Try this, take the fuel pump relay out and put a new fuse in. If it doesn't blow put the relay back in and if it blows then try a new relay. The relay may be shorted to ground internaly. Other wise you'll have to trace the wires to the VCM and the pump relay to look for a chafed wire that's contacting metal. The wire coming from the ECM B fuse is orange and has a splice in it going to the pump relay and the VCM/PCM. Hope this helps.....Andrew
Underhood fuse block swap out relay #7 thats the ECM relay. Ground Circuits Using a DVOM, touch negative voltmeter lead to a good ground. Touch positive voltmeter lead to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If reading is greater than one volt, check for open, corrosion and loose connection on ground lead. See ECM GROUND LOCATION table for ECM ground location. Page 1 of 1 SYSTEM/COMPONENT TESTS - 2.6L EFI -1994 Isuzu Rodeo
I checked all of the fuseable links and they were all good. Next I decided to check all the power wires to the ECM and also the grounds from a wiring diagram because the Mil is controlled by the ecm and the bulb was good. The ecm is located behind the glove box. Bingo, the orange wire was only reading 3-5 volts at the ECM, but 12.5 volts after the fuseable link at the underhood fuse block (passenger side firewall). I ran a temp wire directly from after the fuseable link to the orange wire at the ecm and the ecm turned back on and the Mil or "check engine soon" light came on too. The truck started up and has never run smoother.
Note that at first the truck just stalled out and I could restart it right away with no error codes. Eventually the stalling became more frequent with longer reset times required. Once it threw a "code 54" and I thought it was fuel related as each time the gas stopped and I could still start the truck with gas poured into the TB. Ignition ok. My fuel pump turned on and ran if I tested it. I even checked the pressure regulator and the fuel filter to no avail.The orange wire that powers up the ecm is technically part or the fuel pump relay circuit as it also feeds the fuel pump relay 12.5 volts all the time. The thin orange wire from the fuse block is joined to two other thin orange wires in the large group of wires that heads to the ecm along the firewall behind the engine. I had to dig it out of the many wires to find it and remove a lot of tape. It is amazing to me that this one little orange wire could cause so much grief and be so hard to track down. I could not have afforded to take this problem to the Dealer.
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