C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1993 code 51 problem

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Old Jun 24, 2009 | 07:46 AM
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Default 1993 code 51 problem

I have a 1993 LT1,have replaced ecm and prom,it keeps throwing a code 51,car runs fine,any body have any ideas. thanks
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Old Jun 24, 2009 | 02:13 PM
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Originally Posted by txvette170
I have a 1993 LT1,have replaced ecm and prom,it keeps throwing a code 51,car runs fine,any body have any ideas. thanks
Thats a tough one. Maybe a bad resistor in a relay is allowing voltage to creep back in where it doesn't belong ? Or a ground fault in the fan relay circuit ? I don't know, just tossing ideas.

Do you live near Area 51 ?
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Old Jun 24, 2009 | 02:35 PM
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nope texas
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Old Jun 24, 2009 | 02:41 PM
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Originally Posted by txvette170
nope texas
Me too, Austin. Mine's a 93 also.
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Old Jun 24, 2009 | 02:45 PM
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this may help. http://chevythunder.com/199295_lt1_trouble_codes.htm

Why did you change the ECM and PROM originally? Seems you got some bad electronics there, throwing PROM faults.
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Old Jun 24, 2009 | 03:02 PM
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scan tool gave code 51 prom error,read my manual it said to replace prom if still getting code 51 replace ecm
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Old Jun 24, 2009 | 03:04 PM
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Are you sure it's an ECM error code and not a CCM error code?

SYS flashing in the LCD would indicated a CCM 51 which is a problem reading the key pellet. Usually a dirty/worn key pellet or bad ignition key cylinder.

Service Engine Soon lamp on with a DTC 51 would indicated a ECM eprom or ECM problem.

What method are you using to pull codes. If via the CCM by shorting pin A to Pin G, Module 1 are codes for the CCM and Module 4 are codes for the ECM.

Last edited by Hooked on Vettes; Jun 24, 2009 at 03:11 PM.
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Old Jun 24, 2009 | 03:35 PM
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dtc 51,using a scan tool
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Old Jun 24, 2009 | 03:45 PM
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What's the history of the car?
Did some one burn a new eprom for you?
You say the car runs fine even with DTC 51?
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Old Jun 24, 2009 | 04:13 PM
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I bought a new prom from GM ,runs good ,just gives service eng. soon light, i check the codes and it's a dtc 51,turn it off and restart light is out,you can drive for a mile or 20 miles all sudden the ser. eng. lights up no pattern to it .
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