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Codes 34 and 42

Tiny
LIONFAN
  • MEMBER
  • 1989 CHEVROLET TRUCK
  • 5.7L
  • V8
  • 2WD
  • 200,000 MILES
Have code 34 and 42. Runs good with ESC disconnected. High idle.
Thursday, January 24th, 2019 AT 1:25 PM

10 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

Sounds like you might be having a problem in the E.S.T or ignition module. I've attached two pictures below as a diagnostic aide. Here is a tutorial on how to test wiring:

https://www.2carpros.com/articles/how-to-check-wiring

Hope this helps and thanks for using 2CarPros.
Danny-
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Friday, January 25th, 2019 AT 12:10 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Hello,

I found the wiring diagrams so you so use the guide above. I have seen the ECM go bad causing the this issue. FYI.
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Friday, January 25th, 2019 AT 2:16 PM
Tiny
LIONFAN
  • MEMBER
  • 6 POSTS
Thank you.
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Saturday, January 26th, 2019 AT 7:20 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
Please let us know what you find. We are interested to see what it is.
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Monday, January 28th, 2019 AT 7:28 PM
Tiny
LIONFAN
  • MEMBER
  • 6 POSTS
Truck now has uncontrollable spark knock.
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Monday, January 28th, 2019 AT 7:42 PM
Tiny
LIONFAN
  • MEMBER
  • 6 POSTS
Truck now has uncontrollable spark knock
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Monday, January 28th, 2019 AT 7:43 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
What did you do for repairs? Did you swap out the ECM?
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Tuesday, January 29th, 2019 AT 11:38 AM
Tiny
LIONFAN
  • MEMBER
  • 6 POSTS
Checked all the basics; vacuum lines, wiring, new pugs, cap, rotor and wires. Check timing. Had the truck eleven years was going to give it to son in law before it lost its mind. Do not like spending money to give it away. Just want to get the right part not all of them!
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Tuesday, January 29th, 2019 AT 1:36 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,602 POSTS
No problem send the ECM out to a rebuilder and have them check it.
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Wednesday, January 30th, 2019 AT 9:59 AM
Tiny
LIONFAN
  • MEMBER
  • 6 POSTS
Thanks.
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Wednesday, January 30th, 2019 AT 10:55 AM

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