No Pwr at testpoint on PCM - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 28 (permalink) Old Mar 22nd, 10, 07:19 PM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
No Pwr at testpoint on PCM

what voltage should i have at testpoint of pcm for fuel pump. where does pump get power from pcm or from pump relay?
95camaroman is offline  
Sponsored Links
Advertisement
 
post #2 of 28 (permalink) Old Mar 22nd, 10, 07:22 PM
Gold Lifetime Member
Daryl
 
1968RallySport's Avatar
 
Join Date: Apr 2007
Location: Northern California
Posts: 956
Garage
Re: no prw at testpoint on pcm

battery voltage. fuel pump gets voltage from fuel pump relay.
1968RallySport is offline  
post #3 of 28 (permalink) Old Mar 23rd, 10, 03:12 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 32,167
Garage
Re: no prw at testpoint on pcm

Usually, a relay will get battery power from a fusible link or fuse from a buss line applied to one wire of the relay coil, battery voltage.
The other relay coil wire is connected to the PCM and the PCM applies a 'low' to energize the relay, if measured to ground, about 0.5 volts.
Fuel pump relay closes the power contacts for the f/pump, battery voltage. This design transfers heavy current to the relay contacts.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
 
post #4 of 28 (permalink) Old Mar 23rd, 10, 04:36 AM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: no prw at testpoint on pcm

I have no pwr at testpoint. if i jumper pwr to test point pump runs. Ive jumpered pump relay and pump wont run. not sure if pcm is problem or something else I should be looking at? Help.
95camaroman is offline  
post #5 of 28 (permalink) Old Mar 23rd, 10, 06:10 AM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: no prw at testpoint on pcm

I have an intermittant problem. worked on car yesterday no pwr at test point. jumped pump relay pump wouldnt run. today 12v at test point. pump runs. I now have 2 pumps and 3 relays (got a pump and 2 spare relays at yard yesterday) all work today. Do you think my intermittant problem is from pcm? I have read something about ignitionkey possibly messed up. any ideas. My son got license couple days ago this is killing him.
95camaroman is offline  
post #6 of 28 (permalink) Old Mar 23rd, 10, 06:23 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 32,167
Garage
Re: No Pwr at testpoint on PCM

No power at test point, could be an open fusible link or blown fuse before the test point.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #7 of 28 (permalink) Old Mar 23rd, 10, 09:34 AM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: No Pwr at testpoint on PCM

no blown fuse/open link intermittant problem. had 12v this morning, .o5v now.pump was running relays were functioning, had pwr back to pump car would drive. now lost 12v at test point,and pump.
95camaroman is offline  
post #8 of 28 (permalink) Old Mar 23rd, 10, 10:08 AM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 32,167
Garage
Re: No Pwr at testpoint on PCM

Car have VATS?
Do you have a service manual, at least a Haynes?

There has to be a device between battery and f/pump relay not doing its function.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #9 of 28 (permalink) Old Mar 23rd, 10, 01:55 PM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: No Pwr at testpoint on PCM

not sure what vats is. no service manual, do you think it can be computer going bad?
95camaroman is offline  
post #10 of 28 (permalink) Old Mar 23rd, 10, 01:59 PM
Gold Lifetime Member
John
 
Join Date: Dec 2008
Location: Louisville, Ky.
Posts: 3,403
Re: No Pwr at testpoint on PCM

Yes he has VATS, The pellet in the key,
john68 is offline  
post #11 of 28 (permalink) Old Mar 23rd, 10, 02:16 PM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: No Pwr at testpoint on PCM

thanks john68 I wasnt sure what vats was. Any ideals what problem may be. Could it be key or maybe pcm?
95camaroman is offline  
post #12 of 28 (permalink) Old Mar 23rd, 10, 04:36 PM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 32,167
Garage
Re: No Pwr at testpoint on PCM

If the starter turns when commanded by the key/ign, then VATS is not the problem.
VATS = Vehicle Anti-Theft System
To find electrical source to test point, at least a Haynes manual should be acquired. It'll help you out in times like this one - nothing like having a road map for the electrical system.

Another method of powering the f/pump relay is the PCM applying battery voltage to the coil and the other wire of the coil going to ground to complete the circuit. If the circuitry is this method, then yes, it could be the PCM, but aleviating other inputs to the PCM should be done first.

You should hear the f/pump buzz for 2-3 seconds when key goes to IGN and with 30 seconds in between turn ON times.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
post #13 of 28 (permalink) Old Mar 23rd, 10, 04:46 PM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: No Pwr at testpoint on PCM

not key car turns over fine. not pcm just got one from yard no change. no pwr to test point no pwr to pump. about 14v at red wire on relay have jumped several times. sometime pwr get to pump sometimes no pwr to pump. I work midnights im going to get manual on way to work about 20 miles to store so gonna have to wait till tonight. I cant figure out why I have pwr to relay but not back to pump. sometimes there sometimes not there. 3 relays and just a hot wire jumper and I get same intermittant symptoms at the pump..
95camaroman is offline  
post #14 of 28 (permalink) Old Mar 23rd, 10, 04:50 PM Thread Starter
Greg
 
Join Date: May 2009
Location: indiana
Posts: 27
Re: No Pwr at testpoint on PCM

I have looked at conector /harness going through floor to pump not sure what I should have on the three prongs but the connector looks fine. not burnt looking no chaffed or cut wiring.
95camaroman is offline  
post #15 of 28 (permalink) Old Mar 23rd, 10, 04:58 PM
Super Moderator
Bess-68's rule
 
Everett#2390's Avatar
 
Join Date: Sep 2000
Location: Va Beach VA
Posts: 32,167
Garage
Re: No Pwr at testpoint on PCM

If you have pulled the relay and jumpered the socket to get power to the f/pump and it works sometimes and not, could be the pump itself or wiring. maybe unplugging and plugging the connector might help.

Next time the f/pump does not work, bang the tank to jump start the pump. One of the wires would be the same red wire from relay socket. If jumpered, you should have power there at tank. Another wire, if black, would be ground. Could be the terminal of this wire at body is heavily corroded and not making good contact to complete the circuit. The last wire, tan?, would be for fuel gauge.

Give a man a rescued dog for the health of both their souls. May 2017 ROTM Winner - Thank you!
'
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
CUBS - 2016 World Series Champions - Thank you, Joe Madden enjoy your next chapter.
Everett#2390 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome