1992 GMC Pick Up Code 51

**1slowbusa** · 01-04-2012, 04:38 AM

Hi All,

1992 GMC 1500 Sierra 5.7, 700r4 trans 2WD

I just got my 1992 GMC pick up from Kentucky and the thing will not stay running and is missing horribly. I replaced the cap and rotor button, thermostat on the intake, plugs, wires ignition module, ignition coil and it ran good for a day.

I am reading code 51. Which is Prom (MEMCAL) faulty or incorrect prom (memcal).

Has anyone ever had this issue and if so how did you fix it?

Thanks,

**Smittro** · 01-04-2012, 05:57 AM

The ECM or PROM chip is bad. Replacement ECM can be cheaper than aftermarket chips..

Basicly the ECM is having trouble recognizing the vehicles power train configuration due to a bad PROM or "chip"..

**1slowbusa** · 01-04-2012, 06:32 AM

Thanks, I have already located a ECM for $50. Going at lunch time then going to replace tonight.

**Smittro** · 01-04-2012, 08:40 AM

No prob... Just be sure it's the right ECM for your engine and not something like for the 4.3L v6 Sierra's..

The previous owner of my 92 Z34 thought all ECMs for that car were the same and used the wrong one.

Car ran like garbage since the junk yard ECM they used was configured for the 3.1 rather than the 3.4L (LQ1) the z34 has..

Sure it ran and you could drive it, but not good.

**1slowbusa** · 01-04-2012, 09:04 AM

I got one from a 1992 suburban that had the 5.7. Going to test it out tonight.

**1slowbusa** · 01-04-2012, 01:20 PM

Just got through changing the ECM out with the stock chip and she started right up. We shall see if it stays ok.

**Smittro** · 01-04-2012, 02:13 PM

Originally Posted by 1slowbusa

Just got through changing the ECM out with the stock chip and she started right up. We shall see if it stays ok.

Sweet! If you have anymore questions feel free to ask..

**1slowbusa** · 01-04-2012, 02:34 PM

Thanks again!

**Smittro** · 01-04-2012, 03:11 PM

No prob..

**konigandy6** · 01-05-2012, 05:27 AM

Nice one Steven!!! I'm not too familiar with that generation of small blocks.

**Smittro** · 01-05-2012, 05:49 AM

Originally Posted by konigandy6

Nice one Steven!!! I'm not too familiar with that generation of small blocks.

Thanks, it mostly has to do with my experiance with OBD-I cars/trucks, speed density, and the "chip" factor.

In the past I would keep a few aftermarket performance "chips" for each car's ECM for some "quick" tuning options.

Chips can also be burned with a custom tune aswell but the number of people able to do that anymore is shrinking.

Main thing is to make sure if you're changing a bad ECM is to be sure it's the one that works with your power train..

Many wrong ECM's will plug right in and then all sorts of trouble can happen..

**1slowbusa** · 03-07-2012, 11:14 AM

UPDATE:

So far the truck is running great after changing the ECM. I drive it whenever i can get home. Probably about 500 miles on the ECM and no issues.

Thanks,

**konigandy6** · 03-07-2012, 11:56 AM

Originally Posted by 1slowbusa

UPDATE:

So far the truck is running great after changing the ECM. I drive it whenever i can get home. Probably about 500 miles on the ECM and no issues.

Thanks,

Glad to hear that!

**Smittro** · 03-07-2012, 02:23 PM

Originally Posted by 1slowbusa

UPDATE:

So far the truck is running great after changing the ECM. I drive it whenever i can get home. Probably about 500 miles on the ECM and no issues.

Thanks,

Sweet!