Not getting signal from headunit after audio upgrades

[searay86]

Full break down so far, non b&o. Have dual xpr540 amp (use high input) with lphfd31 T harness and kicker kcs speakers. Anytime I plug the amp in I’ll sometimes get front, rear or no speakers with random white noise. Checked all connections (visual and multimeter). Then I’ll switch the t harness to bypass the amp I’ll still get no signal from head unit till I unplug the battery for 5+ minutes. (Restart head unit with fuses or hold power and fast forward button doesn’t change it). After battery start for 5+minutes headunit works like nothing is wrong. Including if I start with bypass amp then plug in to amp it works fine without white noise. But then restart head unit and back to no signal. Also whole time if I unplug high level and use RCAs plugged into mp3 works fine to speakers. Advice? It’s driving me crazy.

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[RagnarKon]

You have a OBD reader?? ACM should give you trouble codes to explain what's happening.

My hunch is your chosen amplifiers aren't proving a load for the ACM to look at, so the ACM is cutting off output to save itself. If I'm right you'll need some load generators, such as these guys.

 

[Brian_B]

You have a OBD reader?? ACM should give you trouble codes to explain what's happening.

My hunch is your chosen amplifiers aren't proving a load for the ACM to look at, so the ACM is cutting off output to save itself. If I'm right you'll need some load generators, such as these guys.

I thought about that - it's possible.

But I know in my setup, I always have bad speaker DTSCs from my ACM, but they continue to play through my high level inputs on my amp even though they always throw the code. But there could be varying levels of "bad speaker", as the ACM probably wouldn't care too much about high impedance, (no speaker/open circuit) but may shut the circuit down on excessively low impedance to keep from blowing the amp (too many speakers in parallel / short to ground)

I suspect something wonky in the T-Harness wiring - got one of the wire colors crossed or something and it's not all just speaker I/O that got spliced in, or something to that effect, and that's what is bugging the ACM out.

 

[searay86]

thanks a lot you two. Ran with the scanner and got a P0606 PCM code. I really tore the harness out multiple times checking connections. I can’t find anything. One odd thing, the high end plug isn’t full identified anywhere. Only two channels but I just duplicated for rear.

 

[Brian_B]

ooo a PCM code, not a ACM code. That... is different. You may have pulled a harness loose or knicked a wire in an adjacent wire bundle or something.

The T-harness you have shouldn't interface with the PCM at all - it's coming out of ACM. But there's a lot of wiring back there, also in the passengeer kick panel where the TCM is and such.

I would probably start by pulling every harness you can get to apart, take a visual check to make sure nothing looks funny, and re-seating it.

*edit*

Actually, first, I would reset everything by pulling the battery for a few minutes, charging the battery to full, reset all DTSCs, and make sure it just isn't a junk code. If it reappears after that, then I'd start inspecting everything. I know you pulled the battery once already... but I'd do it again just to make sure.

 

[Brian_B]

Only two channels but I just duplicated for rear.

Not uncommon - often they are just called Ch A and Ch B, and will be identical otherwise. It is interesting that they have a separate "ground" connection, not just Speaker (-) on the input - I've not seen an amp that does that. Could be to prevent ground loop feedback or something though.

 

[searay86]

Before I started on it again I bypassed the t harness and just went for a drive. Radio was fine till I turned it off and back on. Back to no audio. Audio tab on the head unit wasn’t even selectable. I think I have something going on with the acm. Then back at home I added the load generators. Worked fine and even cycled a few times and all good. Then reassembled and getting no signal again. Tore apart again to check connections and nothing changed. I got the 20 ohms, should I have gotten a different size? No codes from the scanner either. I did notice the t harness is extremely tight when I put the top of the consul back in. Idk why they’d make it so tight.

 

[searay86]

alright more testing I think it’s the load resistors. Should I try a different size?

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