PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

voltage drops while cranking

Thread Tools
 
Search this Thread
 
Old Aug 30, 2008 | 11:15 PM
  #1  
shoemike's Avatar
Thread Starter
TECH Fanatic
15 Year Member
iTrader: (25)
 
Joined: Dec 2005
Posts: 1,283
Likes: 2
From: Prescott, AZ
Default voltage drops while cranking

it drops to 9volts while cranking.
the car will not start.
i lose connection to one or more modules.(P1626 + U1016)
it just cranks and reeks of fuel.
fuses look good, i have 60PSI of fuel pressure, a new battery,
and VATS and reduced power mode are inactive.(state02/state03)
the PCM can be flashed and logged so i am sure it`s ok. (i have used 2)
could this be the alternator and/or a bad ground?
what grounds are most likely to come undone or break?
this happened before but it started and ran after i recharged the old battery
so i thought my battery was the problem but,
a new battery has not helped this time.
Reply
Old Aug 31, 2008 | 07:52 AM
  #2  
Old Geezer's Avatar
TECH Senior Member
iTrader: (3)
 
Joined: Jun 2004
Posts: 5,639
Likes: 71
From: GA, USA
Default

Starter?
Reply
Old Aug 31, 2008 | 12:05 PM
  #3  
jimmyblue's Avatar
Moderator
iTrader: (11)
 
Joined: Mar 2002
Posts: 12,604
Likes: 7
From: East Central Florida
Default

I'd just follow the fat cables to where they go, pull,
wire-brush (cable and attach-point face) and retighten.

My + terminal connection was very badly corroded by
two leaking AC-Delco batteries in a row. Once the tin
is gone you're down to crusty copper. With some work
and a high powered iron I was able to solder-tin it and
it's OK. Being as new battery does not help, you have to
look for series resistance or excessive current draw. The
resistance is liable to be easier to chase down.
Reply
Old Sep 2, 2008 | 08:29 PM
  #4  
shoemike's Avatar
Thread Starter
TECH Fanatic
15 Year Member
iTrader: (25)
 
Joined: Dec 2005
Posts: 1,283
Likes: 2
From: Prescott, AZ
Default

all grounds that i could reach where good,
the alternator power wire was loose so i tightened it.
and still it just cranks but won`t start.
i got a few more codes.

P1626
P1637
C0239
C0240
U1016
and some voltage measurements i took at the BCM.

Pin Wire Color Circuit No. Function

C2 PPL/WHT 1074 Ignition Key Resistor Return .12ohms @20k
D5 PNK 39 Ignition Positive Voltage 10.8 volts (the battery was a little low)
D6 YEL 43 Program Input 10.9 volts
D7 WHT/BLK 1073 Ignition Key Resistor Feed 10.2 volts
D8 DK BLU 229 Fuel Enable 2.6 volts

i`m supposed to check for an open or a short.
i still suspect a bad BCM, tho i don`t know how to explain recovering from
this 2 other times before.
i can`t retrieve the PCM calibration details. (ctrl+alt+pg up)

Last edited by shoemike; Sep 26, 2008 at 01:06 AM.
Reply
Old Sep 2, 2008 | 10:59 PM
  #5  
edcmat-l1's Avatar
Banned
iTrader: (10)
 
Joined: Jul 2006
Posts: 4,782
Likes: 4
From: Va Beach
Default

Put a volt meter from the + to the - on the battery. KOEO, what does it read? Cranking, what does it read? If its not 12.6 KOEO ( thats key on engine off) charge it and retest. If its 12.6 and drops below 10 volts, charge and retest.
Second option is to take it to get tested.
It isnt a red top is it?
Reply
Old Sep 3, 2008 | 12:05 AM
  #6  
shoemike's Avatar
Thread Starter
TECH Fanatic
15 Year Member
iTrader: (25)
 
Joined: Dec 2005
Posts: 1,283
Likes: 2
From: Prescott, AZ
Default

Originally Posted by edcmat-l1
Put a volt meter from the + to the - on the battery. KOEO, what does it read? Cranking, what does it read? If its not 12.6 KOEO ( thats key on engine off) charge it and retest. If its 12.6 and drops below 10 volts, charge and retest.
Second option is to take it to get tested.
It isnt a red top is it?
LOL
it was (4years old)
my voltage drop could have been just from flogging the battery.
i got a new battery, cranked it a few times then did
a VATS relearn (VATS is inactive) and some voltage measurements,
then cranked it some and it died.
(RUN power was on for at least an hour today)
i got a new one tonight and will measure voltage at the BCM
again in the morning.
i always read 11.8-11.6 volts at the battery with a
voltmeter and through the scan tool. (PCM)
maybe there is a drain, but i have always been able to keep
the radio on (ACC)
and, a few 12volt external sensors (RUN).
i use an inverter to power my laptops while driving as well.

there have been a few times in the past where i was driving and the fuel cut out and,
the car still ran (barely) WBO2 went off the hook and even with
RTACS giving fuel to the VE table it still was lean.
i could recover from this by turning of then restating the car.

aside from an incident of my gauges spiking twice my radio, windows,
alarm, and gauges work fine.
what i have seen most people cant get the car to crank with a crashed BCM.
i even changed the PCM to try to work around the no start issue but
the stock one did help.
i can not retrieve the calibration details (VIN) from either PCM through
the OBDII port, but i can scan and flash the PCM.
i don`t suspect the PCM and, the starter does`nt explain why i keep getting P1626 and can`t read the VIN through OBDII. (does it?)

Last edited by shoemike; Sep 26, 2008 at 01:07 AM.
Reply




All times are GMT -5. The time now is 09:22 PM.

story-0
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin

Slideshow: This heavily modified 1971 Camaro mixes classic muscle car styling with a fifth-generation Camaro interior and modern LS3 power.

By Verdad Gallardo | 2026-05-12 18:06:42


VIEW MORE
story-1
6 Common C5 Corvette Failures and What's Involved In Repairing Them

Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.

By Pouria Savadkouei | 2026-05-07 18:44:57


VIEW MORE
story-2
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph

Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.

By Verdad Gallardo | 2026-04-21 13:57:02


VIEW MORE
story-3
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked

Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...

By Pouria Savadkouei | 2026-04-16 10:05:15


VIEW MORE
story-4
Top 10 Most Powerful Chevy Trucks Ever Made!

Slideshow: Top ten most powerful Chevy trucks ever made

By | 2026-03-25 09:22:26


VIEW MORE
story-5
Hennessey's New Supercharged Silverado ZR2 Has 700 HP

Slideshow: Hennessey has turned the Silverado ZR2 into a 700-hp off-road monster with supercharged V8 power and a limited production run.

By Verdad Gallardo | 2026-03-24 18:57:52


VIEW MORE
story-6
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes

Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.

By Verdad Gallardo | 2026-03-23 18:53:41


VIEW MORE
story-7
Awesome K5 Blazer Restomod Comes With C7 Corvette Power

Slideshow: A heavily reworked 1972 K5 Blazer swaps its off-road roots for a low-slung street-focused build with modern V8 power.

By Verdad Gallardo | 2026-03-09 18:08:45


VIEW MORE
story-8
10 Camaros You Should Never Buy

Slideshow: There are thousands of used Camaros on the market but we think you should avoid these 10

By | 2026-02-17 17:09:30


VIEW MORE
story-9
10 LS Engine Myths That Refuse to Die

Slideshows: Which one of these myths do you believe?

By Verdad Gallardo | 2026-01-28 18:10:11


VIEW MORE