TeamRX8

iTrader: (25)

The connector is just for pin separation and positioning.

No continuity = wire break somewhere.

edit

When you checked the positive pin it wasn't connected to the PCM, was it?


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GK1707

iTrader: (10)

Connected to the PCM as in the PCM being plugged in? Everything was plugged in and the battery was connected when I did the continuity test.

The all the ground connections in the engine bay checked good for continuity back to the battery. And I'm guessing if it's a wire break I'd have to unravel the harness and look for the shorted wire then?

The harness looked as if there was no problems. It's pretty tightly wrapped. But if it's normal that the positive pin shows no continuity to the battery and it's controlled by the PCM, I'm guessing if I don't find a wire break it's a good chance it's the pcm that's my problem then?

GK1707

iTrader: (10)

Hmmm that's interesting but the battery connections are perfectly snug and I checked all the grounds for continuity and they all are good even the grounding strap on the engine block above the oil pan.

I was hoping the connector is the issue but since it sounds like the positive is controlled by the pcm I might have to go digging in the harness for a break in the wiring.

And if that comes up with nothing I'm guessing it's the pcm that's bad. Quick question if I buy a used pcm from a wrecker. With the same year (04 6mt) it's my understanding that the dealership has to reprogram it for the immobilizer to work with my key.

My problem is that I only have the valet key for my car. PO lost the original key and sold me the car with only the valet key and I've never had a problem but I'm guessing I'd need a main key for the pcm to be programmed?

Assuming the pcm is my problem and that it needs to be replaced that is.

TeamRX8

iTrader: (25)

oh fudge, hopefully you didn't fry the the PCM or that terminal connection within it then.

A continuity test is simply checking ohm-resistance in the wire between the two end connections. No voltage is used. Voltage should never be supplied to a PCM pin.

Praying for you ...

GK1707

iTrader: (10)

I didn't apply any voltage to the pins. I simply touched the multimeter prongs to the battery and connector pins. The negative registered continuity repeatedly and the positive pin came back with nothing, no continuity.

But I didn't touch any PCM pins or any connectors going to the PCM, it was plugged in and covered with the lid.

GK1707

iTrader: (10)

Thanks Team for making me paranoid. I just started the car to see if I fried the PCM lol. Starts fine again but same problems. Battery light and P0131, No charge registering on the multimeter.

Waiting on the connector to come in and I'll start with replacing that first. If that doesn't fix it I'll have to start tearing into the harness to look for a broken wire.

TeamRX8

iTrader: (25)

No, you need to perform a proper continuity check first, which you failed to do based on your description. Only if it fails that then you tear into the harness.

put the multi-meter in Ohms/resistance mode, take the connector out of the PCM, connect the multimeter to the appropriate PCM connector pin with one prong and the alternator connector pin on the same wire with the other prong, If the resistance is infinite or high then the wire has a problem. If the resistance is low then the wire between the PCM and the alternator is fine.

GK1707

iTrader: (10)

Ahh gotcha. Yeah I didn't test that. I'll get to it next.

GK1707

iTrader: (10)

Another question. I know the coolant temperature sensor relays alot of info to the PCM and it's in the general area of the thermostat. Is there any chance if wiring from that goes bad it would cause alternator/battery problems.

I have to take a look at it when I get a chance, although I don't think I touch the ect sensor. Im wondering if it's a possibility.

TeamRX8

iTrader: (25)

I wouldn't expect that at all. It impacts the engine operating and emission parameters, but shouldn't imoact alternator performance at all.

GK1707

iTrader: (10)

Ok guys so after a grueling few weeks of college and working 40hrs the 8 has been on that back burner but I finally got a day off to test some more.

Quick recap, the power wire/ring terminal on the alternator positive tests good for continuity at the battery positive.

Two alternators bench tested good at a local auto electric and I also bench tested both of them myself at the local Advance auto parts (perks of being in with the commercial manager is I get to use their equipment).

Tried 3 different batteries on the car all fully charged and tested good.

Tested the PCM pins for resistance and both measure low resistance = good connection to the alternator connector/plug (also replaced the connector).

Quick tip, the multimeter prongs were too big to fit inside the wire harness connectors so I used staples that I straightened out, a paper clip would probably be ideal but I had none.







Low resistance shows that the connector pin from the wire harness has a good connection to the connector at the alternator.

I tested all grounds again. Still the same problem. Alternator is not charging the battery.

So any suggestions on what this could be now? I'm stumped. Is it a bad PCM??

Harlan

iTrader: (3)

This is probably a dumb question, but have you checked your fuses?

9krpmrx8

iTrader: (46)

Yes, and hopefully actually tested them.

GK1707

iTrader: (10)

I actually have checked them, visually only though, but they all seem to look ok. No burns or breaks in any of them. I was looking specifically for the alternator fuse or relay but theres none, atleast that I know of, or could find.

Would there be any specific fuse or relay that would control the alternator or cause this no charge condition?

I did read somewhere on the forum that if the PCM can't read IAT that it would immediately stop charge going to the battery because of overheating and causing the battery to leak.

But from what I've searched the MAF doubles as an IAT sensor as well. And I'm not getting any codes for bad MAF sensor or anything related. I've cleaned the MAF and connector to it as well.

9krpmrx8

iTrader: (46)

Hmmm. I have seen bad fuses that visually looked okay so I would rule them out.

GK1707

iTrader: (10)

I've pulled up both fuse box diagrams, engine bay and in cabin fuse boxes and I can't find any fuses/relays that would affect the alternator or charging, of the battery.

If I can get a hold of one of the other local 8 owners tomorrow I'll swap MAFs with him to see if it makes any difference.

TeamRX8

iTrader: (25)

Just take it to the dealer already, they can tell you pronto after hooking it up to the Tech machine ...

GK1707

iTrader: (10)

As much as I'd like to give the stealership a chunk of change to check what I already checked and charge me to replace each and every piece one by one (because I'm more than sure they do problem solving by replacing parts).

I think I can hold off from having them poke at my car only to tell me my catless exhaust is the reason my battery is not being charged. I'll try to swap MAF sensors with someone local and see if that could make a difference.

Also with the help of one of our moderators I found a company that can repair and reflash the stock PCM as well as copy the data and flash it to a replacement PCM. So I likely wouldn't need a trip to the dealer if I did need a new PCM.

My efforts to see the dealer aren't as much as a priority as the closest one to me is 45min away on the opposite side of town, where the car would have to be towed. Not to mention my life schedule doesn't mesh well with their service hours. Luckily I'm not in a huge rush.. The car sits for now.

GK1707

iTrader: (10)

P0131 was the code for low voltage at the front o2 sensor.

GK1707

iTrader: (10)

Welp.. Figured this **** out. It was the PCM connector. I connected the multimeter to read voltage to the battery and as I let the car idle I started messing with the connectors and moving the wiring.

Apparently even tho they all snapped and "clicked" into place. THAT DOES NOT MEAN THEY ARE SEATED CORRECTLY. I pushed in the lower connector, (the largest one) and watched the voltage spike form 11V up to about 14.5V.

I suspected it was something stupid I was overlooking.

MAKE SURE YOUR PCM CONNECTORS ARE SEATED CORRECTLY!!

edit: Will have a low mileage good alternator up for sale soon lol.

9krpmrx8

iTrader: (46)

Yeah it usually ends up being something stupid simple. Glad you got it sorted.

GK1707

iTrader: (10)

Yeah glad I figured it out but weird thing is it happened again just now. So I went back and reseated the connector to the PCM and voltage went back up. So the connector doesn't seem to want to stay seated.

I changed configuration of the wires so that there is a bit more pressure on the top of the connector to keep it seated and so far it seems good. But its weird it wont stay seated. I removed them all and cleaned them again with contact cleaner and dried them up.

9krpmrx8

iTrader: (46)

Well the harness could have gotten yanked at one point or something, maybe consider using some dielectric grease, just use it lightly.

GK1707

iTrader: (10)

Alright guys, alternator works fine and charges perfect. Reading an average of 14.5V at the Cobb. But Im still getting the P0131 CEL. Low voltage at the front O2 sensor.

The car runs fine and no limp mode. Revs thru all the gears and works perfect but Im wondering if its the O2 sensor thats bad or is it another wiring issue? Its says low voltage to the circuit and I've cleared it after I seated the PCM connections, but its come back so its not my charging issue that caused it it looks like.