Vettedriver986

When I initially start my car it only shows about 11.5 volts, and then after a few moments of driving it kicks back up to above 13V. However it takes so long to do that , that it throws the engine code p1637 and says service vehicle soon. The car is a 04 z06 and has 38k miles on it.
What the hell?

lucky131969

Is this the same car with a new turbo, new engine, etc? If so, you need to disclose that up front.

Vettedriver986

yep

Vettedriver986

i just tested voltage at battery...12.7, and the same at the post on the alt with the car off...

03BlkZ

Mine does the exact same thing at start up. I have been unable to find the problem because I have not had any time to pull the right side header to inspect the starter solenoid. Starter solenoid is where I would start the inspection. Good luck to ya!

Vettedriver986

I just ran a jumper cable from pos battery terminal to post on the alternator and there was no change in my problem... if there was an issue at the starter where it all connects together, this test would have had improved results. Am I not correct?

03BlkZ

I believe you are correct because my issue goes away with the jumper installed. Hopefully Bill Curlee will chime in on this to help you out!

Vettedriver986

yeah, my issue def does not go away. I will say my alt has sat on a bench for a year and half.

Vettedriver986

Guys, I still cannot figure this out. When I ran a jumper cable from pos battery terminal to the post on the alternator (to over ride the starter solenoid) the problem did NOT go away. I had my battery load tested. and it is fine. My connections at the posts on battery and alternator are snug.

The problem is strange. When I first start the car(cold start) it reads 14.0-14.1 volts, but after I drive around it drops to 13.4ish... If I turn the car off and then on again when its hot the alternator shows it only puts out 11-12 volts and then a few moments later boosts up to 13.-4ish again. I have the code p1637... could this simply be my alternator going bad. or am I missing something? I would hate to go buy another one if mine is not bad.

dgrant3830

Pull your alternator and take it down to AZ or wherever and have it tested.

Vettedriver986

i am reading .16 volts when i test the D wire on the pigtail g oing to the alt....

lucky131969

Then you either have an open wire due to damage, a blown fusible link, or a bad connection at the starter. You should read battery voltage at pin D.

Vettedriver986

what should pin D read?

lucky131969

Helps if you read my post......

Vettedriver986

battery voltage yeah hahaah I missed that. 3 hours of sleep here. Yeah. I tested what I thought was pin D and got .16 volts, but turns out that in fact was not pin d. So if my pin D checks out, and over riding my starter solenoid doesnt resolve my issue, its gotta be that my alt is bad huh?

lucky131969

Possibly, but I would want to isolate it. Have you tested the "turn on signal" from the PCM? I'm just wondering if the voltage you see (wherever you are reading it) is battery voltage on start up, before the field voltage turns on the alternator. In any case, I would verify you have 5 volts at pin B on startup.

Vettedriver986

going to my shop to hook up the voltmeter and test this stuff. Ill look for battery voltage at pin D with the car on or off? I will also be looking for 5 volts at pin B on startup..

lucky131969

It's connected to the battery, via a connection at the starter.

Vettedriver986

strangely now im throwing a p0622 code in addition to the p1637 code I initially got...

Vettedriver986

okay, So pin D is reading battery voltage as it should. Pin B is reading .76-.77

So Pin B is NOT reading 5.0 Volts.