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ECM and CHIP

norwegianvette

Well-known member
Joined
Jul 15, 2007
Messages
240
Location
Norway
Corvette
1993 Aqua Convertible
Hi again.

Anyone who know if the PROM and the Chip is the same thing. If you buy a upmarked chip and install it will that be the same as replacing the PROM. I ask as i had a code 0051 Prom on the car and try to find out what that might be. No permanent ligh in service light or anything. Just "Service engine soon" when ignition is switched on and for a brief time after it's started.

Also i had code 0042 Ignition control. Anyone with a good idea what to do with that bugger.

Steve
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
At some point in the early '90's, I think they did away with the replaceable chips and moved the CPU from behind the "bread box" to the engine compartment. I'll dig up my Corvette electrical book and let you know.

All the codes can be searched. Just go to a search engine like www.google.com and type in the code and OBDI.

OBDI stands for On Board Diagnostic I. It was used until 1996 when it was replaced by OBDII, which is still currently being used. OBDII, IMO, is much more advanced and makes it so much simpler to find problems than it's predecessor.

When the check engine light comes on, it's usually (maybe even always?) an emissions related issue. Here in the states, different states have different levels of stringency in our emissions allowed. I know the C5 and C6 cars are classified as low emission vehicles, not quite sure about the C4's, though.
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
My 90 has the ECM above the clutch master cyl and has a removable chip.


Glenn
:w
 

norwegianvette

Well-known member
Joined
Jul 15, 2007
Messages
240
Location
Norway
Corvette
1993 Aqua Convertible
I'm not sure but i think i saw somwhere that this change happened in 1993 as is the same year as my car. My ECM is placed above the battery.

Steve
 

c4cruiser

Well-known member
Joined
Feb 22, 2002
Messages
971
Location
Lacey, WA USA
Corvette
87 Gold Z52 Coupe 02 EB Z51 Supercharged Coupe
PROM and "chip" are basically the same thing when referring to the ECM.

I believe that 1989 was the first year that the ECM moved from the interior to the engine compartment above the battery. OBDII was used in Corvettes beginning in 96 but there was a sort of "hybrid" version in the 95 car. At that time, the removeable chip went away and in it's place was a permanently installed PROM.

With the early ECM you could replace the PROM simply by swapping out the stock chip for a "performance" chip. With OBDII, you need a programmer of some sort to modify the parameters and data values that are stored in the OBDII PROM.
 
S

Sunstroked

Guest
Your 93 vette has an OBD 1 type of ecm. You cannot reprogram the unit without special computer chip burning hardware & software and a unused chip. Then you must install that chip into the ecm. In the case of a hypertech chip, it piggybacks onto the original chip. Now Im not a computer geek, but I do believe that a prom would be able to be changed using a reprogrammer. Those types are called OBD 2 type of ecms. And do not require that you install a new chip, just reprogram the existing one.

If you have an SES light on you must jumper the A & B pins together at the ALDL plug under the dashboard by the drivers side rt knee. Or use a code scanner for OBD1. then turn on the ignition but dont start it. The codes are flashed by the SES light flashes. A code 12 will normally flash 3 times followed by any other logged codes set.

A code 51 is a memcal error. You need to remove the ecm and turn it over. remove the access cover and check to make sure that all pins are fully inserted into the socket and it is properly latched. Then clear the code, by using the obd1 scanner or disconnecting the battery for a minute or so. If the code comes back you either have a memcal gone bad or the ecm itself.

After you deal with the code 51 issue, run your car for a minute. Check to see if your code 42 reappears. If it doesnt, OK. If its still there let us know, further t/s will be required.
 

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