First thing I do when I get one of these old rigs in my shop with odd electrical issues is tighten the harness connectors that have bolts. There's the one at the PCM/ECM, and the one on the drivers side valve cover for the engine harness. These come loose over time and cause all kinds of problems. Next would be to run through all fuses and test relays. Sounds to me like it could be an ignition switch issue or wiring/connections in the column. You wouldn't have a lot of things working if the ignition switch is failing to wake up circuits. I take it you have no communication with a scanner?
2000 7.3 F350 no power at ECM harness
I I have a truck that I purchased that was not running.
The check engine light does not come on when I turn the key on. The PCM relay is good and it has electricity at all times. I don't know whether or not there is supposed to be key on electricity there?
When I go to the wiring harness that plugs into the ECM there is no power going to it. When I turn the key on there is no check engine light. There is also no key on electricity at the fuel pump relay so no power to the inertia switch or to the pump.
I have mechanical diesels but this is my first electronic so I'm learning more about these engines and computers and that sort of thing as I go.
I'm trying to narrow it down to whether it's actually the wire going through the harness from the relay to the PCM, or if there is supposed to be key on power at the PCM relay which would bring other things to check.
I
The check engine light does not come on when I turn the key on. The PCM relay is good and it has electricity at all times. I don't know whether or not there is supposed to be key on electricity there?
When I go to the wiring harness that plugs into the ECM there is no power going to it. When I turn the key on there is no check engine light. There is also no key on electricity at the fuel pump relay so no power to the inertia switch or to the pump.
I have mechanical diesels but this is my first electronic so I'm learning more about these engines and computers and that sort of thing as I go.
I'm trying to narrow it down to whether it's actually the wire going through the harness from the relay to the PCM, or if there is supposed to be key on power at the PCM relay which would bring other things to check.
I
1 - 20 of 39 Posts
I have not gotten any software as of yet but right now I think I could more use a wiring diagram because the computer won't power up anyway there's nothing to read. Once I get the computer powered up that would probably be the next step.
And just to be clear I can turn the key on, the lights come on on the dash the engine will spin over but I get no check engine light and the computer is not powered up.
And just to be clear I can turn the key on, the lights come on on the dash the engine will spin over but I get no check engine light and the computer is not powered up.
Check for power at terminal 16 of the OBD connector
also check the power outlet on the dash
Fuse 2 and 36
also check the power outlet on the dash
Fuse 2 and 36
Check your PCM power fuse, it should be separate from the fuse that powers the relay.
I have no idea of which one it is on your truck, you'll have to look in the owners manual, it may be # 30 in the cab.
I have no idea of which one it is on your truck, you'll have to look in the owners manual, it may be # 30 in the cab.
All fuses are good under hood and in the truck.Check for power at terminal 16 of the OBD connector
also check the power outlet on the dash
Fuse 2 and 36
No power anywhere on the entire ECM plug with key on.
Will check the OBD connector and the power outlet.
The power fuse is good. I not only tested it but I visually looked at it.Check your PCM power fuse, it should be separate from the fuse that powers the relay.
I have no idea of which one it is on your truck, you'll have to look in the owners manual, it may be # 30 in the cab.
The 2000 model truck was kinda in a system change time -- one of the diagram scenarios below should be what is right for your truck -- the number designations are at the PCM connector , which are the same numbers but the way power is supplied is different -- still a test light or meter should prove the power out
Got these from a 1998 diagram
#55 power all the time -- fuse #24 -- power at PCM relay #30
#71 power key on
#97 power key on
Fuse #30 power to PCM relay #86 with key on (thru the diode) -- this powers 71 and 97
And on the 2002 diagram
#55 -- fuse #38 -- power all the time
#71 -- power from PCM relay thru fuse #22
#97 -- power from PCM relay thru fuse #22
PCM relay is closed from power from the key, and then sends power thru #71 and #97
Fuse #64 powers the key -- to PCM relay terminal #86
PCM relay terminal #30 is hot all the time
PCM relay terminal #85 is ground -- thru the diode
Got these from a 1998 diagram
#55 power all the time -- fuse #24 -- power at PCM relay #30
#71 power key on
#97 power key on
Fuse #30 power to PCM relay #86 with key on (thru the diode) -- this powers 71 and 97
And on the 2002 diagram
#55 -- fuse #38 -- power all the time
#71 -- power from PCM relay thru fuse #22
#97 -- power from PCM relay thru fuse #22
PCM relay is closed from power from the key, and then sends power thru #71 and #97
Fuse #64 powers the key -- to PCM relay terminal #86
PCM relay terminal #30 is hot all the time
PCM relay terminal #85 is ground -- thru the diode
Well the PCM diode was bad.
Now I have key on electricity at the relays but I do not have electricity at the computer nor do I get a check engine light.
And there is no ground on the IDM relay slot where there should be one.
Now I have key on electricity at the relays but I do not have electricity at the computer nor do I get a check engine light.
And there is no ground on the IDM relay slot where there should be one.
You still need to trace wiring. If you have power going THROUGH the relays but none reaching the ECM, you have an open circuit.
Ayup, relay could be bad
gotta start at the beginning and follow the power to the PCM
pull the PCM relay and check for power
then can we assume the relay clicks with the key ?
next check the output terminal of the relay for power
gotta start at the beginning and follow the power to the PCM
pull the PCM relay and check for power
then can we assume the relay clicks with the key ?
next check the output terminal of the relay for power
All of the relays are good.
The PCM diode was bad and as I am testing the slots for the relays, the IDM relay has no ground.
The PCM diode was bad and as I am testing the slots for the relays, the IDM relay has no ground.
Keep this thread going you don’t need another thread for the continuation of this problem. Thanks
Okay I now have key on power and I know that the IDM is activated by a ground through the ECM.
I'm working on tracing in the wires because when I test for power there's no power anywhere on the whole ecm plug. There is no ground except for the very very last pin and one of the larger pins coming in separately is a ground.
I'm working on tracing in the wires because when I test for power there's no power anywhere on the whole ecm plug. There is no ground except for the very very last pin and one of the larger pins coming in separately is a ground.
Post #8
should have power on pin 55 in the PCM connector
the others will only have power after the PCM operates the relays
Do you have the diagram ?
should have power on pin 55 in the PCM connector
the others will only have power after the PCM operates the relays
Do you have the diagram ?
Yes, thank you.Post #8
should have power on pin 55 in the PCM connector
the others will only have power after the PCM operates the relays
Do you have the diagram ?
I will be checking tomorrow but I have no power on any of the pins at the ECM connector and I have no grounds on any of the pins except for the very very last pin and there is another wire that is not part of the main wiring that goes out that wire there is also ground.
* update *
I made a mistake. I was not testing the ECM harness I was testing the IDM harness.
I have key on power at the PCM relay and the relay is clicking everything is working. I tested every pin on the ECM harness and anywhere that is supposed to have power has it anywhere that is supposed to be grounded is grounded.
I also probed each pin for ground to see if maybe anything was shorted out. The only thing remotely questionable to me is #3 pin was contactor low current return and #8 glow plug monitor Left Bank (low side).
Still no check engine light.
Any ideas?
I made a mistake. I was not testing the ECM harness I was testing the IDM harness.
I have key on power at the PCM relay and the relay is clicking everything is working. I tested every pin on the ECM harness and anywhere that is supposed to have power has it anywhere that is supposed to be grounded is grounded.
I also probed each pin for ground to see if maybe anything was shorted out. The only thing remotely questionable to me is #3 pin was contactor low current return and #8 glow plug monitor Left Bank (low side).
Still no check engine light.
Any ideas?
If you have all proper powers and grounds to the PCM, and cannot communicate with it via scan tool, with no CEL or WTS light, the PCM is bad.
I don't have a scanner right now I have to order that but everything is in that harness that's supposed to be there and working all the relays and fuses are good but there is no check engine light and no wait to start light.If you have all proper powers and grounds to the PCM, and cannot communicate with it via scan tool, with no CEL or WTS light, the PCM is bad.
Anybody have a good place that's reasonable I can send them this PCM to be repaired?
Is your fuse to the fuel pump good ? In the dash5 amp , it runs the dash startup etc ? Fuel heater in filter shorts out ? Gov Holmes
1 - 20 of 39 Posts
Ford Power Stroke Nation
A forum community dedicated to Ford Power Stroke owners and enthusiasts. Come join the discussion about diesel performance, modifications, EGR deletes, troubleshooting, lift kits, tires, wheels, maintenance, and more!
Full Forum Listing
