3 communication errors U1000, U1021, & U1045

[Hatchet]

Tapped the gray wire with a clamp on T splice.

 

[MAY03LT]

Gotcha. So with 12v on the gray wire, and ground on the black wire didn't make the pump run, see if you have continuity through the pump before yanking it. Unplug the connector, and see if you have continuity through the two inside pins - the pins are small, so make sure that the leads aren't touching each other inside the connector - that will show continuity and can throw your diagnosis off course.

 

[Hatchet]

Gotcha. So with 12v on the gray wire, and ground on the black wire didn't make the pump run, see if you have continuity through the pump before yanking it. Unplug the connector, and see if you have continuity through the two inside pins - the pins are small, so make sure that the leads aren't touching each other inside the connector - that will show continuity and can throw your diagnosis off course.

I really need a second pair of hands to test this all. Before i put my gas tank in, I tested the pump, and it worked and was quiet. My fuel pressure gauge has disappeared, but the truck is still not starting. I will test for continuity before I go out to dinner for the gf's birthday. I'll see if I can scrounge up a fuel pressure gauge and a spark tester here at work while i'm at it.

I just know this is gunna be something so stupid and easy that I just can't see right now...

 

[Hatchet]

Haven't jade a chance to mess with it yet. But a friend of mine brought over a really good code reader. Treads all codes.

Here are most of the 25 codes that came up, in no particular order.

U codes
1026
1041
1000
1301
1000
1041
1002
1255
1041

B codes
2725
0799
0785
0775
0780

C codes
0306
0305
0300
0379
0359
0321
0327
0374

My buddy took photos of the codes ado I have a description for most of these codes. I'll update this later with more info.

Also, sprayed throttle cleaner into intake, and it ran, nothing with key.

 

[jrSS]

Haven't jade a chance to mess with it yet. But a friend of mine brought over a really good code reader. Treads all codes.

Here are most of the 25 codes that came up, in no particular order.

U codes
1026
1041
1000
1301
1000
1041
1002
1255
1041

B codes
2725
0799
0785
0775
0780

C codes
0306
0305
0300
0379
0359
0321
0327
0374

My buddy took photos of the codes ado I have a description for most of these codes. I'll update this later with more info.

Also, sprayed throttle cleaner into intake, and it ran, nothing with key.

Holy shit batman! ! Hopefully you can find out what's up.

 

[Hatchet]

I'm thinking my bcm might be dead and causing a data crash in the data system

 

[Hatchet]

Haven't jade a chance to mess with it yet. But a friend of mine brought over a really good code reader. Treads all codes.

Here are most of the 25 codes that came up, in no particular order.

U codes
1026-Loss of class 2 communications with automatic traction control
1041-Loss communications with electronic brake control module (EBCM)
1000-(no state of health from module)
1301-Class 2 data link high (Better be for medicinal reasons)
1000-class 2 data link malfunction
1041-loss of EBCM / EBTCM communication
1002-no DTC definition found. see service manual
1255-class 2 communication malfunction
1041-lost communication with body control module (BCM)

B codes
2725-Mode switch circuit malfunction
0799 (0790 cant tell blurry pic)-transfer case something circuit something
0785-2hi indicator circuit malfunction
0775-4hi indicator circuit malfunction
0780-4lo indicator circuit malfunction

C codes
0306-motor a / b circuit malfunction
0305-front propshaft speed sensor system malfunction
0300-rear propshaft signal circuit malfunction
0379-front axle circuit malfunction
0359-4lo discrete output circuit malfunction
0321-transfer case lock circuit malfunction
0327-encoder circuit
0374-general system malfunction

My buddy took photos of the codes ado I have a description for most of these codes. I'll update this later with more info.

Also, sprayed throttle cleaner into intake, and it ran, nothing with key.

updated with what the code reader said. Most of the items the reader would recommend 1 of 2 items as a typical repair. Ignition switch and TCCM replacement. I have already replaced the ignition switch not to long ago and it ran for a while. Don't think it would have gone out so sooner. So i'm thinking the TCCM is causing the potential data crash. However when I did the data test of pushing out the pins, I did do the TCCM and it still did not work. I will try that again. But the one code that really has me wondering is the U1041 loss of communication of BCM. I wonder if that is what could be causing the potential data crash.

If so I'm wondering if the BCM is junked or just got corrupted data and a tech 2 could reprogram it. If it does need to be replaced, if I remember correctly, the BCM needs to be programed to my VIN in order to work correct?

Thoughts on my thoughts?

 

[Hatchet]

Gotcha. So with 12v on the gray wire, and ground on the black wire didn't make the pump run, see if you have continuity through the pump before yanking it. Unplug the connector, and see if you have continuity through the two inside pins - the pins are small, so make sure that the leads aren't touching each other inside the connector - that will show continuity and can throw your diagnosis off course.

Tested on old pump first and got 7 ohms. Tested the pump in the vehicle through the harness and got 1.7 ohms resistance. I just drove it into the garage started first try. Brought out in and restarted it a few times no issues. Then I kept doing key on and listening for the pump and it was going the next 5 times then out randomly stopped again

 

[MAY03LT]

Then I kept doing key on and listening for the pump and it was going the next 5 times then out randomly stopped again

So what lead to the pump replacement the first time? I wasn't up on the whole history so was it replaced for the same symptoms?

Assuming that this is unrelated to the pump replacement, I'm leaning toward a problem with the pump itself because I don't see a wiring issue causing that (5x on then nothing) to happen. I guess to keep it DIY friendly, you can do a wiggle test when it's running and see if it stalls to rule out the wiring. Or test the fuel pump relay inputs to make sure that it's not a control problem. Other them that, I'd be pulling the pump to inspect it.

There's another way to test the pump without pulling it but it requires some fancy tools.

 

[Hatchet]

Took the trick to gm and they said dead pump. The relay clicks when it goes to key on. Next time I get it to start I'll do the wiggle test. Did you see above with the 25 codes? Im thinking the no data from bcm might have an issue with this. Bad data causing a crash. I screwed with it all at the same time and checked all but 1 ground and there all good.

 

[Hatchet]

A friend is coming over friday with nicer and better diagnostic tools, that I can't afford. So we shall see what comes of that.

 

[Hatchet]

Long story short, we fixed the fuel pump power issue. We don't know why its working like this, but its working.

Ok, so here is the craziness that happened on friday evening.

Got home at 4, I started the truck, it started right up no issues. Left it running till 430 when Jeff came over (I wanted him to see that it was running and the fuel pump was working). So after talking a little bit and putting the code reader on. I notice gas pouring down the side of the tank. So I drop the tank and fixed the feed line so it stopped leaking under pressure. And in the process determined the fuel pump is working great and has a strong pump. Gasoline soaked clothes as proof. So we put the tank back in and it started right up. We mess around with the wires and everything trying to get it to fail. Nothing. So we go to the next attempt.

Driving it has that is when it has failed each other time. Pull it out of garage and it died, but started right back up. So I proceeded to drive up and down the driveway and all sorts of speeds for 20 mins trying to induce a permanent failure of the system. Neighbors and people walking around looking at me like i'm crazy. Finally get it to permanently fail, as soon as I get half way into the street. Neutral and pushed it back up the garage for testing.

We had cleared the codes earlier, did a new scan and had 3 codes. All were various U1041 codes. None of them made any real sense but we appeased them and checked all the power and grounds to the BCM and TCCM. All were good and properly grounding at there proper locations. So we went back to the fuel pump. Hooked up his power probe to the battery and went to work checking grounds and power at the connector and frame ground all all was good. Power coming from the battery through the relay, the ground going to the frame and the frame to the battery all good. Checked continuity as well all was good. Tested the pigtail adapter to the fuel pump, powered it with the power probe, and checked continuity. All were fine. Plugged it in. Nothing. No fuel pump running.

Now for the weird part. So everything we have done and checked shows it should be working fine. I still had the extra ground wire tapped into the pigtail and put it to the frame. Nothing. Attached it to his power probe ground right back to the battery. It worked. disconnected it would stop, re connect the ground to his probe and the pump would work. Ok weird check grounds again at the frame, the ground at the frame is showing correctly connected to the battery. After doing this a few times and trying to understand how the frame could be grounded to the battery correctly, the fuel pump correctly grounded to the frame. Still not work unless the ground ran back to the battery.

At that point we gave up trying to understand and ran a ground wire back to the battery. But of course you can't attach it directly to the battery (terminal connection doesn't allow it). So we check it with the fender ground near the drivers side windshield. Touching the pump worked, detached it would stop. So I bolted the ground there and now it appears to run on each key start. The real test will be the road test, and I would like someone with a vehicle capable of pulling the TB back to the garage in a worse case it still dies while driving.

So that's where i'm at. We don't know why it's working like that. But gave up trying to figure it out.

 

[The_Roadie]

How exactly are you checking the grounds? With the meter on resistance, or by checking the voltage from the wire to a good frame or battery ground? Most meters aren't very accurate on the resistance scale, and what looks like <1 Ohm may still be enough resistance to block current flow enough to turn on the pump.

 

[MAY03LT]

Man what an ordeal. The only drawback of the power probe is it doesn't load down a circuit. So you could have a single strand of copper touch ground and it will test good - but that's just good enough to satisfy the power probes beeper thingy and led. You try running a couple amps through that single strand and you'll know how good the ground is lol.

It sounded like your jumper tests proved that p/g was good. I guess time will tell.

I didn't go through the u codes because the problem was happening when the relay would click. If the relay wasn't clicking, and the pcm contol pin was the issue, then I'd be looking at the u codes. There still may be an issue there, but I'd focus on the pump first.

 

[Sparky]

If there is a frame grounding issue (causing the pump to not operate) I could see that also causing other random issues like those various codes due to systems sporadically losing ground.

 

[Hatchet]

How exactly are you checking the grounds? With the meter on resistance, or by checking the voltage from the wire to a good frame or battery ground? Most meters aren't very accurate on the resistance scale, and what looks like <1 Ohm may still be enough resistance to block current flow enough to turn on the pump.

We did a resistance test, but also something else. I am drawing a blank on what the test was on the voltmeter. I know it had only a symbol listed. I'll look at my voltmeter when I get home.

Man what an ordeal. The only drawback of the power probe is it doesn't load down a circuit. So you could have a single strand of copper touch ground and it will test good - but that's just good enough to satisfy the power probes beeper thingy and led. You try running a couple amps through that single strand and you'll know how good the ground is lol.

It sounded like your jumper tests proved that p/g was good. I guess time will tell.

I didn't go through the u codes because the problem was happening when the relay would click. If the relay wasn't clicking, and the pcm contol pin was the issue, then I'd be looking at the u codes. There still may be an issue there, but I'd focus on the pump first.

Yea time will tell. I'm hoping that was the end of it all. Yea the relay was clicking every time. Looking at the schematics on alldata or what ever program he had. There wasn't alot of things that could interfere with the fuel pump running after the relay. Again time will tell as i put it through its paces.

If there is a frame grounding issue (causing the pump to not operate) I could see that also causing other random issues like those various codes due to systems sporadically losing ground.

That I don't know. I can't think of how the frame wouldn't be grounded good enough to the battery.

 

[HARDTRAILZ]

Fixed?

 

[Hatchet]

Just did an up and down the driveway a few times. Afraid to take it around the block with out someone else around to pull me just incase. I'm not waiting 2 hours for a tow truck to pull me back 2 blocks.

 

[Sparky]

Get out and push

If I were closer I'd help you.

 

[Hatchet]

Ive pushed that thing down the street before. Thought I was gunna die by the end because of the slight slope.