P1351 after replacing ignition coil and icm

[Tanner Peterson]

I still haven't resolved it. My next thing is replacing the connector to the brake control module. Just gotta find the time and weather to do it.

What ABS connector are you guys referencing? I’ve read the thread twice but must be missing the post referencing that…

 

[doncaruana]

Ok. I'm an idiot. Lol. I said brake control module and it's the ignition control module. And I think that threw off exp500 or it was an autocorrect. I'm relatively certain the issue is the line between my ignition control module and the the ecm. I'm just nervous about disconnecting or even messing with the wires around that thing since the truck is almost 2t years old.

 

[Tanner Peterson]

No big deal. that makes alot more sense!

I just retested my ICM connector today with a test lamp and it all passes. I replaced that connector at the beginning of this problem.

 

[doncaruana]

Resurrecting this thread for an update...it appears as if this was actually due to an issue with the fuel pump relay, surprisingly. It's all in this thread but the reader's digest version is that the 5 pin relay you use for the fuel pump doesn't function properly (something funky with that 5th pin in the panel or whatever it's attached to - and it's just for testing anyway) but a standard 4-pin relay (like the A/C relay) works fine.

 

[exp500]

Don, Likely only a temp fix with relay swap. Look thru the diagrams for fuel pump and find the common areas- grounds especially. Being that your voltage goes Hi to set P1351. Also look for corrosion at the fuse block.
Did you ever unplug and clean the ECM plugs?

 

[doncaruana]

Don, Likely only a temp fix with relay swap. Look thru the diagrams for fuel pump and find the common areas- grounds especially. Being that your voltage goes Hi to set P1351. Also look for corrosion at the fuse block.
Did you ever unplug and clean the ECM plugs?

I never messed with the ECM plugs because I honestly didn't want to poke that turd, so to speak. I'd be willing to bet there's an issue in the fuse block itself based on the behavior. I mean it went like this:
Before, w 5-pin relay - intermittent, but regular occurrence of hard start, which throws P1351
Put in 4-pin relay - perfect start every time, no code
Put new 5-pin relay in - A little trouble starting but started. Drove home from shop, would NOT turn over at all
Put new 4-pin relay in - Back to normal functioning - good starts, no P1351. I will say though that I got P0507 at this point, which is completely new and a bit of a headscratcher.

 

[exp500]

Don- check your service manual for the ground locations relative to your issues. There is a main one on the frame about at drivers feet and, acouple under the dash I think you can reach from the floor or with cluster removed. Another one is the firewall ground strap rt side by trans dipstick.Follow both the Light switch and Fuel pump relay wiring too.
It is getting to be common now to have corrosion at the fuse block and ECM connectors due to age and Dielectric grease drying out.

 

[doncaruana]

Reading through the service manual and after talking to the mechanic who found that the relay switch worked, I think I'm coming to a better understanding...maybe? He said the P1351 was a result of the long cranking that would take place (which jibes with what I saw). Reading the service manual, I see this: "An inoperative fuel pump relay can result in long cranking times. The time necessary for the oil pressure to reach the pressure required in order to close the oil pressure switch and supply the necessary current for the fuel pump causes the extended crank period."

That 5th pin just goes out to a capped wire, as east302 showed me here. I have to believe the issue is in the fuse/relay block but I'm having a hard time resolving exactly how this works and doesn't work. That 5th pin, pin 87a, is the one that connects through to the fuel pump when the relay is *not* being energized, ie the fuel pump prime connector. As I type this, I'm thinking that the issue is really next to the middle pin, pin 87a. Because when you turn it over, the relay flips to pin 87, which is the battery feed, and sends it on to the fuel pump. The thing is, at that point, pin 87a isn't engaged.

But if the blade in the relay being inserted actually causes pin 87 to ground out or even causes pin 85 (the signal to energize the relay) to do the same, that would make the relay not work right. That either stop the relay from opening at all, or it would just ground the power out before it gets to the pump.

Does that make sense? And, more importantly, how in the world would you even address that?? Wouldn't you have to pull that whole block off, wires and all??

 

[east302]

It’s probably worth a look under the fuse block to see if anything stands out (or is even visible). Going by memory here, but I think it sits on three or four legs that just bolt through the fender liner and are accessed from above the tire.

 

[doncaruana]

A friend suggested deoxit. Think I'll order some to have on hand...