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I might have something for you, and it ties in with that PCM "driod" thing.
That is the PCM diode, and it supplies power to the IDM and PCM - so we may be on the right track. The diode function is to supply power in one direction, but to prevent the flow of power in the opposite direction - like a check valve in plumbing... or a one-way door on an animal trap. If one were to accidentally hook the batterries up backwards to the truck, this prevents the very expensive PCM and IDM from being damaged (allegedly). So... a meter across the diode in one direction should read some pretty low ohms, but reversing the leads should read like open air - nothing to see here, folks.
The best news (assuming the diode is bad)... there is a spare one right next to it. You'll lose your A/C, but big woop when you consider you're getting your rig home to troubleshoot the rest of your issues. Caveat!!! Alert! Alert! You must turn the diode close to the middle around and it must point the opposite direction (the little arrow thing there) before installing it on the other side. I didn't look, but I'd bet good money it fits in there in one direction anyway. Fat good it does to have a consumer diode that can be accidentally installed backwards.
However... if it can be reversed... pulling it, inspecting it, and putting it in backwards would prevent the PCM and IDM from powering up. A meter will tell you if it's fried or not. The PCM diode passes power only when the key is on and none of the fuses in line are blown.
If you turn your key on and your not getting power to the small forward post on the glow plug relay the you have a problem with the ignition "Run" circuit. I suspect your not getting power to several things which may explain not having a wait to start light. Need to check power from the ignition switch run circuit. I'll see if I can find a wire diagram
question on this? can we run a temporary jumper from the key on wire from ign to the little post on relay to test n see if things go back to normal? also does anyone have steering column wiring diagrams so we know what the run wire is on the ign part?
I might have something for you, and it ties in with that PCM "driod" thing.
That is the PCM diode, and it supplies power to the IDM and PCM - so we may be on the right track. The diode function is to supply power in one direction, but to prevent the flow of power in the opposite direction - like a check valve in plumbing... or a one-way door on an animal trap. If one were to accidentally hook the batterries up backwards to the truck, this prevents the very expensive PCM and IDM from being damaged (allegedly). So... a meter across the diode in one direction should read some pretty low ohms, but reversing the leads should read like open air - nothing to see here, folks.
The best news (assuming the diode is bad)... there is a spare one right next to it. You'll lose your A/C, but big woop when you consider you're getting your rig home to troubleshoot the rest of your issues. Caveat!!! Alert! Alert! You must turn the diode close to the middle around and it must point the opposite direction (the little arrow thing there) before installing it on the other side. I didn't look, but I'd bet good money it fits in there in one direction anyway. Fat good it does to have a consumer diode that can be accidentally installed backwards.
However... if it can be reversed... pulling it, inspecting it, and putting it in backwards would prevent the PCM and IDM from powering up. A meter will tell you if it's fried or not. The PCM diode passes power only when the key is on and none of the fuses in line are blown.
NOTE TOO THIS: WE Know this box here with PCM BLACK RELAY is WORKING we swapped blower relay too...
so we can rule out this relay here....
ok we will try tomorrow i also just asked a question about the hot when in run on relay as well thanks guys im sorry im a pain with point blank dumb questions. and my typing skills suck too n again guys sorry.
You say you know the PCM power relay is working? If you read my post it will tell you what pins to check for voltage. If the relay is closing but there is no voltage on pin 30 then it does you no good. Pull the relay out and look at the back. I believe the pins are marked with numbers. Check the pins in the fuse panel that match the ones on the relay and see if you have power at pin 30. If not check fuse 24 in the same box again.
You say you know the PCM power relay is working? If you read my post it will tell you what pins to check for voltage. If the relay is closing but there is no voltage on pin 30 then it does you no good. Pull the relay out and look at the back. I believe the pins are marked with numbers. Check the pins in the fuse panel that match the ones on the relay and see if you have power at pin 30. If not check fuse 24 in the same box again.
got another buddy that will help me today with thias truck. we are going to be looking at a few things 1st this post. 2nd the ign run system 3 the fusible links. we are gonna try in see if we can direct jump from the key wire inside truck to glow plug relay. if this works we will get it at least home closer so we can fix it at home n not 30 miles away. i've thought about a tow bill ad flat towing but i did not want too drop driveshaft. and i dont wanna flat tow on highway.
Looking at a wire diagram when you turn the key on the power from fuse 30 in the fuse panel under the dash goes to pin 86 at the PCM power relay which is relay number 30 in the fuse panel under the hood. Turn the key on and check for 12 volts at pin 86 for that relay. If you have no power there then figure out why.
If you have power there it should close the relay and take the 12 volts that is on pin 30 at all times and send it out to multiple items including the PCM and glow plug relay. If you have no power at pin 30 figure out why.
It sends the power out through pin 87. You could just put 12 volts straight from the battery to pin 87 and see if the small post at the front of the glow plug relay gets power and the wait to start light comes on. At that point the truck might start if all is powered. If this works and you have power at 86 and 30 with the key on this would indicate a bad PCM power relay.
We ran this we have power to fuse 30 under dash. Everything is OK. Now we don't have power too relay that is 86 with key on. We have power w key off at pcm relay. Under hood. We don't have power at the small pcm droid fuse. In Underwood fuse box.
Update. As of today. We have power to fuse 30 under dash goes to pcm relay under hood. Only when key is off. When key on no power to 86 on relay. We have found on relay. No power to pcm diode w key on or off. With non power to pcm diode with this make relay not work? So we think it's a wire from under dash too outside box. Does this sound about right?
You say you know the PCM power relay is working? If you read my post it will tell you what pins to check for voltage. If the relay is closing but there is no voltage on pin 30 then it does you no good. Pull the relay out and look at the back. I believe the pins are marked with numbers. Check the pins in the fuse panel that match the ones on the relay and see if you have power at pin 30. If not check fuse 24 in the same box again.
im gonna have too update you on this cause i know more facts here. please bare with me as i might get stuff comfused. but as of now we do have power to inside fuse box that leads too outside fuse box to pcm relay the little black relay. we do have power to the outzide relay yes with key off. we have ground too this relay too. we turn on key we loose power to pin86 on relay and we have no power at all at the black pcm droid. nothing even with fuse out. nothing DEAD nothing. so we know we have power inside truck. but not out too pcm outside fuse box. everyting else as fuse is ok just no power with key on at pcm relay and no power to droid.
So if I have this right you have power to pin 86 with the key off but lose it when the key is on? That would indicate that the wiring and the diode is good. Next I suspect the ignition module under the dash. Looks something like this https://www.1aauto.com/ignition-swit...FQwXgQodT-cGXA
Thought I read earlier that you had change some part of the ignition system. What was it?
So if I have this right you have power to pin 86 with the key off but lose it when the key is on? That would indicate that the wiring and the diode is good. Next I suspect the ignition module under the dash. Looks something like this https://www.1aauto.com/ignition-swit...FQwXgQodT-cGXA
Thought I read earlier that you had change some part of the ignition system. What was it?
yes looks like this and he tested every metal plug and yes i only replaced the key cyl
So if I have this right you have power to pin 86 with the key off but lose it when the key is on? That would indicate that the wiring and the diode is good. Next I suspect the ignition module under the dash. Looks something like this https://www.1aauto.com/ignition-swit...FQwXgQodT-cGXA
Thought I read earlier that you had change some part of the ignition system. What was it?
we were thinking about just adding a real hot wire from that fuse box line to the pcm relay if we dont find answers. would that work?
we were thinking about just adding a real hot wire from that fuse box line to the pcm relay if we dont find answers. would that work?
That would temporarily solve the problem on this one circuit but the power goes a lot of other places. You would have to figure out what other systems are not getting power and run wires to all of them.
Need to figure out why power is dropping out with key on
So if I have this right you have power to pin 86 with the key off but lose it when the key is on? That would indicate that the wiring and the diode is good. Next I suspect the ignition module under the dash. Looks something like this https://www.1aauto.com/ignition-swit...FQwXgQodT-cGXA
Thought I read earlier that you had change some part of the ignition system. What was it?
no im sorry my buddy just told me we dont have power at pin 86 on pcm on run. we do have ground on both run or not run. i thought he meant he had power being we do have power at fuse block at pcm relay number 30 when not in run. we do not have power with pcm droid but droid tested ok.
That would temporarily solve the problem on this one circuit but the power goes a lot of other places. You would have to figure out what other systems are not getting power and run wires to all of them.
Need to figure out why power is dropping out with key on
ok where can i find a good wiring from that fuse in the truck to just a foot north too other fuse box that goes to relay for pcm. cause we know we have power inside underdash at what ever fuse it is while in run mode...
Pin 30 of the PCM relay should have power all the time. Pin 86 should have power with the key in the start or run position. Pin 85 should have ground all the time.
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