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Discussion Starter · #1 ·
Hi Y'all
My truck is a F250 7.3L Diesel with 261k and lived in Arizona until 2019 when I inherited it. It was built in Oct. 2001 and uses the 2001 fuse panel layout. Fuse 22 is a 20 amp fuse for the engine control module and it blows intermittently. I am stuck and need a wiring diagram or help on what it goes to and why it keeps blowing. When it pops the relays under drivers dash do a rapid clicking then I replace the fuse and its fine till the next time. A friend of mine suggested to put a 25amp fuse and see what happens. Everything else works as it should. Much appreciated, Tweeze
 

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I would NOT put in a bigger fuse.
 

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Higher amperage fuses is one way to start a truck fire or cause yourself a lot more problems

Sent from my SM-J737V using Tapatalk
 

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Which fusebox? Fuse 22 in the underhood box is a 50A that feeds the underdash fuse box. Fuse 22 in the under dash fuse box is supposed to be a 10A fuse that feeds the blower motor relay and air bag deactivation switch. If someone has changed it from a 10A to a 20A, you're already in dangerous territory. Is blowing the fuse coincidental with you turning on the HVAC fan?
If everything starts clicking under the dash when the fuse blows, that's a sign of low voltage to the relays. There's a possibility that your fuse box has been wet and has corrosion inside that lets current leak between the traces.
 

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Poster has a 2001 truck.

In my 02 truck, fuse 22 is 20A and protects fuel injectors and PCM
 

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Poster has a 2001 truck.

In my 02 truck, fuse 22 is 20A and protects fuel injectors and PCM
I realize he said his was an '01 and uses the '01 fuse layout (two fuse boxes) so that's the information I posted. But if he doesn't have both an underhood and an underdash fuse box then he doesn't have the '99-'01 fuse layout. Maybe he made a mistake in stating it used the '01 fuse layout. I don't know when exactly the changeover occurred.
 

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From the build date and description it's a 2002 with the 2002 fuse panel. HAS to be. F2.22 (20A) is for PCM VPWR inputs, IDM relay (coil side) IPR Valve, Manifold Intake Heater Relay (coil side) and the glow plug relay or module (as equipped)
 
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From the build date and description it's a 2002 with the 2002 fuse panel. HAS to be. F2.22 (20A) is for PCM VPWR inputs, IDM relay (coil side) IPR Valve, Manifold Intake Heater Relay (coil side) and the glow plug relay or module (as equipped)
I should have suspected that. Model year changes happen in early summer now (and have for quite a while).
The OP's description of relay chatter could be caused by crossover between fuse box traces, right. If the fuse blows, then it could be fed (at reduced voltage) thru another circuit.
I notice he hasn't been back yet to either clarify his issues or say it's been resolved. :(
 

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Discussion Starter · #9 · (Edited by Moderator)
Which fusebox? Fuse 22 in the underhood box is a 50A that feeds the underdash fuse box. Fuse 22 in the under dash fuse box is supposed to be a 10A fuse that feeds the blower motor relay and air bag deactivation switch. If someone has changed it from a 10A to a 20A, you're already in dangerous territory. Is blowing the fuse coincidental with you turning on the HVAC fan?
If everything starts clicking under the dash when the fuse blows, that's a sign of low voltage to the relays. There's a possibility that your fuse box has been wet and has corrosion inside that lets current leak between the traces.
Thanks. Fuse 22 in my truck is engine control module. My truck was built in Oct. 2001 and goes by the 01 fuse panel layout. It shows its a 20 amp fuse. I've wiggled every wire everywhere and while it's running and nothing happened.
Higher amperage fuses is one way to start a truck fire or cause yourself a lot more problems

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Thanks I never would as not looking for a fire. Thanks 🤙
 

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My truck was built in Oct. 2001 and goes by the 01 fuse panel layout.
Your truck is a '02 model and only has one fuse box, under the dash. That's the '02 and later fuse panel layout.

What? It never rains in Arizona? If there's a windshield leak you won't know it until it rains, and then the damage to the fusebox is done. You should check the fuse box for any evidence of water damage.

BTW, there's no need to quote yourself when posting. I've edited a couple of your post above to eliminate duplication.
 

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I should have suspected that. Model year changes happen in early summer now (and have for quite a while).
The OP's description of relay chatter could be caused by crossover between fuse box traces, right. If the fuse blows, then it could be fed (at reduced voltage) thru another circuit.
I notice he hasn't been back yet to either clarify his issues or say it's been resolved. :(
Water in the fuse panel is not going to blow the fuse. Good advice to check it though to avoid future problems. So now that we have established the model year... The components I listed should give the OP areas to inspect the wiring harness. To be honest, most wiring faults on this model year with a 7.3L are on the engine from my experience. With an intermittent short to ground the first places I might look are the engine harness where it drapes over the left valve cover and the IPR take out. Circuit 361 (red) Add to the list of components on 361 listed above: brake pressure switch on the master cylinder... still looking. Circuits with splices can be hard to trace down.
 

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Discussion Starter · #13 ·
Your truck is a '02 model and only has one fuse box, under the dash. That's the '02 and later fuse panel layout.

What? It never rains in Arizona? If there's a windshield leak you won't know it until it rains, and then the damage to the fusebox is done. You should check the fuse box for any evidence of water damage.

BTW, there's no need to quote yourself when posting. I've edited a couple of your post above to eliminate duplication.
Thanks. No windshield leak, no sign of water under dash or on fuse box. I know it rains in Arizona. Lol🥴
 

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Discussion Starter · #14 ·
Which fusebox? Fuse 22 in the underhood box is a 50A that feeds the underdash fuse box. Fuse 22 in the under dash fuse box is supposed to be a 10A fuse that feeds the blower motor relay and air bag deactivation switch. If someone has changed it from a 10A to a 20A, you're already in dangerous territory. Is blowing the fuse coincidental with you turning on the HVAC fan?
If everything starts clicking under the dash when the fuse blows, that's a sign of low voltage to the relays. There's a possibility that your fuse box has been wet and has corrosion inside that lets current leak between the traces.
Thanks and found no signs of water or corrosion. I started it yesterday wiggle wires under dash n engine bay. Kept running. What next?
 
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