2018 l5p high county U18A2 help

[blairsperformancellc]

so as I said I had a pin bent over on the can bus plug. (Replaced it with new) got the code cleared but now I have a U18A2 perinate code. i got with my tuner and we have tried a couple things to get it to go away and nothing will work. if anyone has an ideas i would greatly apricate it. first l5p btw.

 

[2004LB7]

Lost communication with the in tank fuel pump control module.

This might be the correct module that is above the spare tire

Amazon.com

 

[2004LB7]

Or possibly this one: GM (13540026)

GM Parts | Fuel Pump Power control Module - (13540026) | GM Parts Store

2017-2023 GM Fuel Pump Power control Module 13540026

www.gmpartsstore.com

 

[TheBac]

Moved to L5p Section.

 

[gmduramax]

Use a snap on to clear the permanent code.

 

[JoshH]

The first thing I would do would be to get rid of the can bus plugs and plug all the stock modules back in. I've seen can bus plugs cause more problems than they fix. I wish people would quit selling them.

 

[gmduramax]

The first thing I would do would be to get rid of the can bus plugs and plug all the stock modules back in. I've seen can bus plugs cause more problems than they fix. I wish people would quit selling them.

A lot of them come with the pins in upside down .

 

[Chevy1925]

The first thing I would do would be to get rid of the can bus plugs and plug all the stock modules back in. I've seen can bus plugs cause more problems than they fix. I wish people would quit selling them.

What from? Bad connections?

 

[Mikey52]

The fuel pump control module is a known problem, mine went out at about 35,000 miles.

 

[kidturbo]

If it's on the HS CANbus, ya should be able to communicate with that fuel pump module using something like a SnapOn or GM tools. If so, then ya know it's speaking and problem isn't bus connection related. If it doesn't speak OBD messages, then will take more work to verify if it's connected. First being resistance between CANhi CANlo wires at pump should read about 60ohms. If open, ya have an open circuit..

On the DTC part, permanent "U" DTC's won't clear with any scan tool. Takes XXX miles traveled and XX key resets to make it go away. I recently ran into, and confirmed this on L5P TCM. Verified with a GM Tech buddy who said "some ya can, most ya can't.." From what I've read on other GM forums, 99% can't. So that leave ya verifying the fuel pump is connected and talking, then waiting 200 miles and a dozen key cycles or more to see the code go away..

 

[kidturbo]

The first thing I would do would be to get rid of the can bus plugs and plug all the stock modules back in. I've seen can bus plugs cause more problems than they fix. I wish people would quit selling them.

Ya made a guy who spends all day working on CANbus hardware, actually google term canbus plugs...

The way GM daisy chained all their nodes, going clear back to early 2007 years is completely insane and against all known CANbus network engineering design practices. Ya Tee these nodes together, and if one fails due to bad connection, the rest can still talk as normal. GM on the other hand has ran the BCM to TCM to GPCM to ECM. 4 wires on every node in a chain. One node goes down, wire gets cut, and your totally screwed. Just poor design, Unless your attempting to keep someone from removing a node from the bus... Then, still piss poor engineering skills for critical comms on any network..

 

[2004LB7]

Ya made a guy who spends all day working on CANbus hardware, actually google term canbus plugs...

The way GM daisy chained all their nodes, going clear back to early 2007 years is completely insane and against all known CANbus network engineering design practices. Ya Tee these nodes together, and if one fails due to bad connection, the rest can still talk as normal. GM on the other hand has ran the BCM to TCM to GPCM to ECM. 4 wires on every node in a chain. One node goes down, wire gets cut, and your totally screwed. Just poor design, Unless your attempting to keep someone from removing a node from the bus... Then, still piss poor engineering skills for critical comms on any network..

I had to google that one too

 

[Chevy1925]

Ya made a guy who spends all day working on CANbus hardware, actually google term canbus plugs...

The way GM daisy chained all their nodes, going clear back to early 2007 years is completely insane and against all known CANbus network engineering design practices. Ya Tee these nodes together, and if one fails due to bad connection, the rest can still talk as normal. GM on the other hand has ran the BCM to TCM to GPCM to ECM. 4 wires on every node in a chain. One node goes down, wire gets cut, and your totally screwed. Just poor design, Unless your attempting to keep someone from removing a node from the bus... Then, still piss poor engineering skills for critical comms on any network..

Yes, it’s really fun when a knock sensor module goes or the bail connection above the lml def tank gets corroded.

So damn dumb… gm ain’t the only that does this though

 

[kidturbo]

I know where there is LMM truck driving around today with 2 pieces of mig wire in place of the GPCM. About 5 years back, a buddy called me with no start issues, and after a bit of digging I found the GPCM was shorting the CANbus wires. All he had handy was a mig welder, and roll of electrical tape. Made up a homemade "canbus plug"... lol. Said that should get ya by for week or two until ya find a module. He's never fixed it.

 

[TheBac]

I had to google that one too

You mean to tell me that I knew an electrical item that you and Ken didnt? Holy crap, hell just froze over.....

 

[NC-smokinlmm]

That’s crazy, I’d never get away with setting up a network like that. I have to setup a backbone and drop to all my accessories so if one goes wonky the captain doesn’t loose everything. I even separate power supplies from one section of the vessel from another in case the short is severe enough to take out the entire system. I can’t believe a major manufacture gets away with such poor networking designs.

 

[Mikey52]

So the way GM does it is like the old token ring network?

 

[2004LB7]

So the way GM does it is like the old token ring network?

They do share some similarities but instead of a ring it's liner. Probably closer to a class B fire panel system

 

[2004LB7]

You mean to tell me that I knew an electrical item that you and Ken didnt? Holy crap, hell just froze over.....

Never heard them by that name. Always referred to them as jumpers.

 

[kidturbo]

By sheer odds, I went to technical college in the mid 80s when TBI had just released, with plans to become a full fleged automotive design engineer. ASE Master Tech certs and all that jive in 87. But by 95 was switching careers to my first love computers. Got involved with building this new fad call the Internet, and sold off my SnapOn box full of tools that same year to fund an ISP startup.

Spent next 25yrs building the beast on multiple continents, ending up managing the backbone for ATT until i got burnt out by the big corp BS. So when I look at these convoluted CANbus network designs from that same era, can only surmise, most of the smart automotive network engineers must have bailed in 99 also. Taking those 10k signing bonus checks to join hot dot com startups, like so many of my friends in the ISP industry. As stated above, GM 2-wire CAN is about as close to old token ring, as it is to being a good CANbus network design.

The Internet and CANbus prototols are both designed around failsafe and redundancy at the core OSI layer 1. The new to the job GM engineers seemed to have missed that week of networking 101 class.. And the rest is history. Hopefully, the new kids can master Ethernet protocol correctly, since CAN is headed out, and the Internet side is now up to gigE, and mostly fiber optics... lol

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