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No communication with code reader at DLC

Tiny
PAPAWCHEVEROLET
  • MEMBER
  • 2001 CHEVROLET BLAZER
  • 4.3L
  • V6
  • RWD
  • AUTOMATIC
  • 215,000 MILES
So the number four and five pin are a common twelve volt ground at the DLC. I should be able to hook up a test light to the positive side of a battery and get a light at both pin four and five you guys have some good information and are helping a lot. Thanks for everything.
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Wednesday, February 15th, 2017 AT 4:36 PM

8 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Please keep your question in the same thread instead of asking a separate question each time. It makes it very difficult to follow. Thank you.

They are both direct grounds. Should show continuity to ground when tested.

https://www.2carpros.com/questions/dlc
https://www.2carpros.com/questions/computer-issues
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Wednesday, February 15th, 2017 AT 5:21 PM
Tiny
PAPAWCHEVEROLET
  • MEMBER
  • 4 POSTS
  • 2001 CHEVROLET BLAZER
  • 3.4L
  • 6 CYL
  • RWD
  • AUTOMATIC
  • 215,000 MILES
I have checked for power at the fuse block and have power at the corresponding fuse position, but I get no ground at pin number four of five on the DLC. If it could be a bad connection due to rust build up, where are these connections found on the vehicle so I can check for a bad connection (rust issues)? Thanks for any help
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The DLC ground is left center of dash. But also check left hand and right hand rear of heads as PCM grounds there. Pin four is ground.
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Pin four grounds through a splice pack (202 Left center of dash) to the ground connection at the right hand side of the dash. That splice also handles the park interlock, the headlights and door locks.

Pin five grounds through the relay block to the fuse block and to the left rear of the engine. It also is the ground point for the remote door locks, cruise control and the PCM.

For both to be bad I would check the wiring for damage under the dash, either cut or disconnected.
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
PAPAWCHEVEROLET
  • MEMBER
  • 4 POSTS
  • 2001 CHEVROLET BLAZER
  • 4.3L
  • 6 CYL
  • RWD
  • AUTOMATIC
  • 251,000 MILES
My OBD 2 code reader will not connect to the computer. Check engine light came on while driving the vehicle home about a seventy five mile ride just bought the car. Runs great. But, I am a little confused I have never seen this happen before and of course it will not pass emissions until this issue is resolved Any help would be greatly appreciated. Thanks
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Check fuse 17 for power it is in the box behind the dash, left side. That is the power feed to the DLC. No power, no com. Also, check pins four and five in the DLC for ground. No ground, no com. (Those ground out on the engine and do tend to rust). If still no com, try a different scan tool. (Many parts stores will read codes for free so they could verify the no com issue.

Then post the code(s).
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
PAPAWCHEVEROLET
  • MEMBER
  • 4 POSTS
No current at fuse block. No ground at DLC either.
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 13,573 POSTS
Okay, check the cigar lighter fuse (#2) for power. The diagram should help you chase the wires to find power and grounds.
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Wednesday, February 15th, 2017 AT 5:54 PM (Merged)

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