1990 GEO PRIZM ECM LOCATION

  • Tiny
  • allportd
  • 1990 Geo Prizm

Electrical problem
1990 Geo Prizm 4 cyl Two Wheel Drive Manual 124000 miles

I am getting a fault code 12, does this realate to
No reference pulses to Electronic Control Module (ECM).
I was wondering where the ECM is located so I can check for bad connection or bad wires.
If you have advise on what the cause of this is it would be great
Thanks, Dwight

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Friday, March 28th, 2008 AT 11:57 AM

6 Replies

  • Tiny
  • merlin2021
  • Expert
  • 17,587 posts

Behind the center of the dash...check the green wire at distributor for 12volts...


http://www.2carpros.com/forum/automotive_pictures/62217_ECM_1.jpg

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Friday, March 28th, 2008 AT 12:48 PM
  • Tiny
  • allportd
  • Member

I checked the green wire and it is fine. Any other suggestion would be great. The engine runs fine most of the time every so often it guits then it will start backup and run fine. It has had new fuel pump, new fuel filter and injectors have been cleaned.

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Friday, March 28th, 2008 AT 2:43 PM
  • Tiny
  • merlin2021
  • Expert
  • 17,587 posts

Igniter

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Friday, March 28th, 2008 AT 3:35 PM
  • Tiny
  • mmprince4000
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  • 8,715 posts

You will always get code 12 when the engine is off, ign. Is on, and the diagnostic ports A and B are connected.

As Merlin said it is probably the ignitor (ignition module in the distributor).
Check with auto parts stores, but I have found it is cheaper to buy a reman'd complete distributor ($260 at NAPA) vs the ignition module itself ($304 at NAPA).

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Saturday, March 29th, 2008 AT 7:15 AM
  • Tiny
  • merlin2021
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  • 17,587 posts

Good tip!

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Saturday, March 29th, 2008 AT 7:45 AM
  • Tiny
  • allportd
  • Member

Thanks for all the help.
As we bought the car in Puerto Vallarta, Mexico and it is hard to get parts here, I will buy the parts when I go back to Canada. It seems the be working much better with fewer stalls. The car sat here for two years without running. I have clean a lot of connections as well as the installing other parts as per my previous post.
Thanks again

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Saturday, March 29th, 2008 AT 5:56 PM

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