Vehicle electrical problem

Tiny
NASTY1
  • MEMBER
  • 2002 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 132,000 MILES
GTP 3.8l SC. Car had been parked for a while, upon getting vehicle back on the road, noticed engine was hesitant while accelerating. Also was not properly charging battery, so I thought. I actually think it was a unknown drain on the battery killing it. Got a jump start, headed to parts store to check alt. On the way blew the ignition main relay. Replaced relay with another. Blew that one as well, plus Another. Had to tow vehicle. Started checking under hood fuse box for shorts. Disconnected ignition control module wiring harness to check its power wire for voltage, and found the pink wire (12v+) to be grounded out. In fact nearly all positive wires under hood are grounded out. I've narrowed it down to the headlamp main fuse, battery main 1, and battery main 2 fuses. So I believe the short to ground is in those circuits or somehow related to all three. Could it be PCM issue, BCM issue, or just a frayed wire grounding out the cars positive wires? Two weeks no car. Please help.
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Sunday, May 19th, 2019 AT 11:39 PM

10 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good morning,

What relay exactly did you replace several times?

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

If all the positive wires were grounded, you would have a lot of fuses blow from this. What fuses have failed?

How did you determine there was a short?

Roy

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Monday, May 20th, 2019 AT 3:30 AM
Tiny
NASTY1
  • MEMBER
It is actually blowing the ignition main relay. After replacing relay three times, every time the car would run less than a block. It would start up and idle then when I jumped in took off it would blow another, I would replace and it would start up and repeat. I disconnected the 12v negative lead from terminal and installed a 12v test light between lead and terminal it lights up bright. So I began in i/p fuse box under dash. Removed all fuses and breakers with no results. Next I went to under hood fuse/relay box, and continued removing fuses/relays one by one, and again nothing. Super frustrating. So next day at it again. It wasn't until I had a few of the big main fuses removed at once did the light go nearly all the way out. Those fuses are#3, #4, #7. Which are headlamp, battery main 2, and battery main 1. With those three out the light dims dramatically, reinstall any one and back to bright on the test light. The light went even dimmer when #33 mini fuse is pulled. That one is ECM sense. Which tells me that those circuits must all run off same power supply. I am a local Mobile mechanic, but ill admit auto/electric is not my strong point. This is not a clients car tho. This is my wife's car! So my pride has definitely taken a blow. Let me add that no other fuses have blown that I know of. Just the #11 ignition main relay. Thanks so much!
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Monday, May 20th, 2019 AT 6:02 AM
Tiny
ASEMASTER6371
  • EXPERT
Did you mean you put a test light in the negative battery cable with it disconnected?

Again, what relay? There is no ignition relay for just the system.

Roy
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Monday, May 20th, 2019 AT 8:19 AM
Tiny
NASTY1
  • MEMBER
Yes, I disconnected the negative battery cable, and between the cable end and negative terminal installed 12v test lamp. It lights up, demonstrating that 12v+ is being conducted through the grounded negative battery cable. Right? I also probed around on different positive wires and known hot at all time fuses under the hood. I did this with battery positive cable removed, and test light clamp on positive 12v+ terminal. Using the probe to test different positive circuits. They all light up the the test light. Demonstrating that the positive circuits being tested are grounded somewhere in the system. Short to ground. Right?
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Monday, May 20th, 2019 AT 8:50 AM
Tiny
NASTY1
  • MEMBER
Unless I pull the #3 #4, #7 maxi fuses. Headlamp, battery main 2, and battery main 1.

The ignition main relay is #11 in the under hood fuse/relay box. Thank you for your patience.
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Monday, May 20th, 2019 AT 8:55 AM
Tiny
ASEMASTER6371
  • EXPERT
No, that is incorrect.

The test light will always light. All that means is the voltage is present at all the modules.

Current is what needs to be measured, not voltage.

Lets go all the way back to the beginning.

What is the original issue you had?

Roy
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Monday, May 20th, 2019 AT 9:05 AM
Tiny
NASTY1
  • MEMBER
Which method are you referring to as being incorrect? Are you referring to the test lamp between neg cable and post? Or probing the positive wires and fuses with 12v+to see which are grounding the current? I don't understand what's wrong with my methods. Lol
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Monday, May 20th, 2019 AT 9:39 AM
Tiny
ASEMASTER6371
  • EXPERT
Just because you have 12 volts does not mean it is grounding current. It just means the presence of voltage. It does not indicate current flow at all.

Roy
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Monday, May 20th, 2019 AT 9:42 AM
Tiny
NASTY1
  • MEMBER
Okay, car was running but didn't seem to be charging battery correctly, brand new battery dead in like two hours of driving and an hour of sitting. That night after charging battery back up. My wife started it while I was looking underneath hood. I saw an arc down on the negative grounding stud on transmission bell housing. It was loose. Next morning tightened it up, jump started the car expecting that all problems were solved. Nope, got one block down the road and started blowing relay. Since it is getting better ground, something isn't agreeing. Something has to go, but when I swap in a new relay will start back up.
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Monday, May 20th, 2019 AT 9:50 AM
Tiny
ASEMASTER6371
  • EXPERT
Okay, what relay? Where is this relay? Can you post a picture of the location?

What is the alternator charging when the engine is running?

https://www.2carpros.com/articles/how-to-replace-an-alternator

Roy
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Monday, May 20th, 2019 AT 9:56 AM

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