Check Engine Light

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shearhawk

Active member
Joined
Apr 4, 2006
Posts
39
  I have a 91 Coachmen w/454.  The engine light came on about a month ago, and is running rich.  Black smoke out of the exhaust and plugs are black. Sometimes it will flood, gas just pours in thru the throttle body injectors.  Problem is, I did the jumber wire on the data link connector and the light flashes code 12 and continues with no other codes.  I disconnected the battery to clear, but check engine light still returns.  Any help will be appreciated.  Maybe I should by a code reader?

Thanks,
Randy
 

John From Detroit

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Joined
Apr 12, 2005
Posts
25,212
Location
Davison Michigan
There are two types of error codes on GM OBD-1 diagnostic devices,  Soft and hard,  Soft errors are ones that clear when you turn off the key, step one in the "Jumper the lead" test method is turn off the engine.

You really need a proper code reader from a shop to read that (see if you can acquire one for a day)

had a problem with my car,  Had engine replaced and to be honest it  just did not run right,  Did not have a check engine light though

Turns out when we hooked up the big diagnostic aid all the readings were default normal save one,,, Something called the "Engine counter" was displaying 0 0 0 0 0 0 0 0 0 0 0 0 which means "Engine not running" (same as code 12 basically) yup, the idiot at the dealer forgot to hook up a ground lead
 

shearhawk

Active member
Joined
Apr 4, 2006
Posts
39
Just found out what the problem was with the Check Engine light.  Bad Coolant Sensor, I know sounds crazy, but apparrantly if this sensor goes bad it will affect the fuel system, as well.  Will check out the fuel symptoms, on our next trip starting Monday.

Thanks,
Randy

PS Was able to flash this code after the engine had been warmed up, then did the jumper.
 

King

Well-known member
Joined
Jan 30, 2006
Posts
354
Location
MA
Not crazy at all.  If the coolant sensor says the engine is cold, the computer runs the mixture way rich until the temp comes up.  Just as you describe.
Art
 

John From Detroit

Well-known member
Joined
Apr 12, 2005
Posts
25,212
Location
Davison Michigan
Bad coolant sensor would be one of the "Soft codes" because if it's showing cold when the engine is not running,,, nothing wrong with that, but soon as the engine starts to warm up it's going to get conflicting input from assorted sensors and error out
 
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