220 amp alternator code P1638HC
Thread Starter
Pro
Joined: Sep 2018
Posts: 676
Likes: 306
From: Nova Scotia Canada
220 amp alternator code P1638HC
Hoping someone can confirm my theory that this code is simply a result of the new alternator producing MUCH more current than the oem so this code is indicating as such. I can't see how it would cause any issues aside from the code.
Is my theory correct?
Thanks!
Is my theory correct?
Thanks!
Melting Slicks
Joined: Sep 2021
Posts: 2,555
Likes: 1,213
This sticky post about C5 alternators explains what condition sets the code:
The Gray wire (terminal C) just sends a signal to the PCM as to how the alternator is performing. It is also referred to as the F terminal. This is called a Duty Cycle signal which is a Pulse Width Modulated (PWM) signal. The Regulator controls the output voltage by turning the alternator OFF and ON to control the voltage. This Duty Cycle signal can be from 0 to 100% with 100% being the regulator has the alternator fully “ON” providing voltage and 50% would mean it is “OFF” half the time.. The PCM only monitors this and will throw a DIC Charging Fault message and code P1638 (99-04) if it detects performance outside of preset parameters.
Thread Starter
Pro
Joined: Sep 2018
Posts: 676
Likes: 306
From: Nova Scotia Canada
Thank you for the clarification on what the "H" &"C" mean. I had wrongfully speculated "Hight Current".
Also thank you for the wiring information. That will allow me to use a meter and see what the voltage regulator is doing but that won't help much as I don't know what the normal duty cycle would be.
I am aware that getting DTC codes is common with aftermarket alternators. There are a few articles on how to eliminate the DTC codes in these cases.
"The fact that you "can't see how it would cause any issues aside from the code" tells us nothing without you also telling us about your qualifications. Naturally, if you are an automotive electrical engineer that was involved in designing the C5 electronics your opinion would carry more weight than if you were a random person that stayed at a Holiday Inn Express last night."
I completely agree and although my back ground is in Marine Mechanical Engineering (submarines in particular) and I've been doing my own work on cars for 30yrs there is still A LOT I don't know. This is my first GM product too.
My GUESS for the additional current not causing any issues is simply because normally having current available won't cause a problem. Drawing too much current can (blown fuses etc). I SUSPECTED that having the extra current would come in handy for running my larger fuel and meth pumps.
So you probably noticed I used the words "guess" and "speculation" a few times. I was hoping to tap into the breadth of knowledge and experience that is available here to verify or disprove what I was figuring.
Also I prefer the Marriot line of hotels
Also thank you for the wiring information. That will allow me to use a meter and see what the voltage regulator is doing but that won't help much as I don't know what the normal duty cycle would be.
I am aware that getting DTC codes is common with aftermarket alternators. There are a few articles on how to eliminate the DTC codes in these cases.
"The fact that you "can't see how it would cause any issues aside from the code" tells us nothing without you also telling us about your qualifications. Naturally, if you are an automotive electrical engineer that was involved in designing the C5 electronics your opinion would carry more weight than if you were a random person that stayed at a Holiday Inn Express last night."
I completely agree and although my back ground is in Marine Mechanical Engineering (submarines in particular) and I've been doing my own work on cars for 30yrs there is still A LOT I don't know. This is my first GM product too.
My GUESS for the additional current not causing any issues is simply because normally having current available won't cause a problem. Drawing too much current can (blown fuses etc). I SUSPECTED that having the extra current would come in handy for running my larger fuel and meth pumps.
So you probably noticed I used the words "guess" and "speculation" a few times. I was hoping to tap into the breadth of knowledge and experience that is available here to verify or disprove what I was figuring.
Also I prefer the Marriot line of hotels
Melting Slicks
Joined: Sep 2021
Posts: 2,555
Likes: 1,213
use a meter and see what the voltage regulator is doing but that won't help much as I don't know what the normal duty cycle would be.
I am aware that getting DTC codes is common with aftermarket alternators. There are a few articles on how to eliminate the DTC codes in these cases.
I am aware that getting DTC codes is common with aftermarket alternators. There are a few articles on how to eliminate the DTC codes in these cases.
Page 22 of this .pdf from said manual claims to be from the 2004 section and has some info about that DTC. I don't know if this is relevant to a 2002 Z06 (or if that's even the car in question) so bear that in mind as you read the information.
I find the online manual rather hard to follow but my paper copy is for a 2000 model. Happy to post some photos of pages if you think they might help.
