Corvette C4 Forum 1984 through 1996

check engine light

Old Nov 1, 2009 | 06:49 PM
  #1  
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Let me start this off by saying i'm a new vette owner, and new to the world of cars in general. That being said, i have a problem with my 1984 Corvette.
The check engine light came on, so we checked the code and it came out with error code 42. Unfortunately, i have found 4 different reasons for that code.
The first is that the Spark Control Module was bad, so I replaced it to no avail. Second was the ECM was bad, so i replaced it, to no avail. The third is that the EST is bad, had it tested, and it works great. This puts me to the final option, a bad ground circuit.
Any ideas on where it might be, and where i can find a wiring diagram?
Thanks guys, i'll learn eventually ;-)
 
Old Nov 1, 2009 | 07:44 PM
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on a related note, does anyone know if there is supposed to be an oxygen sensor on both sides? There's only one, on the driver side and my mechanic friend thinks there's supposed to be two.
Thanks
 
Old Nov 1, 2009 | 08:15 PM
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Your best bet will be to get the Shop Manual,all the diagrams etc. are in there. My shop manual sez Electronic spark timing,not Electronic spark control for code 42,it gives a teast procedure which can point to the ECM.
84's have only one O2 sensor,it's on the driver's side,so you're ok there.
Ron
 
Old Nov 10, 2009 | 02:58 PM
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I have a 900seT auto cab 1997. The check engine light has been coming on but there are no problems with the car and my mechanic is somewhat dumbfounded by it. Has any one else experienced such probs? _______________________________________Website I designed for pay day loans ontario company.
 
Old Nov 16, 2009 | 09:18 AM
  #5  
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Originally Posted by another vette owner
Let me start this off by saying i'm a new vette owner, and new to the world of cars in general. That being said, i have a problem with my 1984 Corvette.
The check engine light came on, so we checked the code and it came out with error code 42. Unfortunately, i have found 4 different reasons for that code.
The first is that the Spark Control Module was bad, so I replaced it to no avail. Second was the ECM was bad, so i replaced it, to no avail. The third is that the EST is bad, had it tested, and it works great. This puts me to the final option, a bad ground circuit.
Any ideas on where it might be, and where i can find a wiring diagram?
Thanks guys, i'll learn eventually ;-)
the first thing you need to do is get rid of that 84 worst year ever for the vette & go with an 86 or up all 84s ive seen youll fix one electrical problem & another will pop up
 
Old Nov 17, 2009 | 10:13 PM
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The ground wire for the EST is usually on the thermostat housing. There is only 1 oxygen sensor. 2 or more sensors were not used until 1996 GM cars with OBDII diagnostic system. 1 sensor was after the converter and used as a catalyst monitor.
 
Old Nov 18, 2009 | 11:30 AM
  #7  
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thanks guys, I got it fixed. The problem was an open in one of the circuits, and we fixed it by cleaning a test connector just above the batery.
 
Old Nov 20, 2009 | 10:01 PM
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Thanks for taking the time to let us know you got her going !
 
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