code 51

[JOHN SLATER]

Brief summary...Picked up a clean 84 T-type cheap. Been sitting for approx 5yrs, 99 tags. After some minor adjustments it ran fair, check engine light was on--Scan tool not able to communiacte w/ECM--Grounding A&B at ALDL did nothing. Injectors were dead. I replaced injectors 42.5lbers I took out of my 87 a couple years ago. I replaced the ECM and ordered a chip for the injectors( I found 87 GN chips dont work in 84's and ECM's arent interchangable w/out adding a MAT sensor) Now I get code 51--ECM not recognizing prom. Checked the installation 10x cleared memory each time--still 51--I even tried all of the 87 chips for 42.5's--and got code 51 on all of those chips...I also plugged back in the old ECM and now it communicates code 51!!! 2 ECM's--a total of 6 chips tried--all reading code 51. What am I missing???

 

[d0n_3d]

sounds to me like both those ECMs are crap...get a good one from Red Regal T in the parts for sale section...he sells them cheap...like $50

CODE 51

Trouble Code 51 indicates that the ECM sensed a fault in the PROM.

When the PROM was initially created, a checksum number representing the total of all the cell values was also stored. The ECM uses this checksum as one way to determine if the contents of any cell has changed. A Code 51 causes the ECM to enter Back-Up mode which uses the CALPAK for default sensor values.

The conditions for setting this code are:

power has just been applied to the ECM, and
the calculated checksum does not match the stored checksum.
- or -
the engine was just started, and
either of two specific PROM locations do not contain the expected value. (One location should have 1's in the odd numbered bits and the other has 1's in the even numbered bit positions.)

Typical causes for this code include:

1) Incorrectly installed PROM module
2) Defective PROM module
3) Defective ECM

 

[JOHN SLATER]

Thanks for the reply, The chip I just installed came from PTE. Do you know if an IC chip installed in a Hot Air car will set a 51?. I suppose both ECM's could be junk, but both setting 51 is unusual
Maybe I should call PTE to make sure this chip was burnt for a hot air car and not an IC car.

 

[d0n_3d]

Originally posted by JOHN SLATER
Thanks for the reply, The chip I just installed came from PTE. Do you know if an IC chip installed in a Hot Air car will set a 51?. I suppose both ECM's could be junk, but both setting 51 is unusual
Maybe I should call PTE to make sure this chip was burnt for a hot air car and not an IC car.

Joe to my knowledge does NOT burn chips for the 84-85 computers...just a STOCK chip configuration...that's it...

he does 86-87 ECM chips only...and a chip burned to run on a 86-87 computer is NOT compatible with an 84-85 computer...hope this helps some...

 

[JOHN SLATER]

d0n-3d I had PTE (Joe) burn some 50lb chips in the past and was very happy with them before I went the extender route. I ASSumed he burnt hot airs also---the info page for the chip has me verify year as well as vin#--in the comment section I noted again It was a hot air...I'll call to make sure on monday. I've got another ECM comming--In the mean-time I'm looking for harness problems. I cant locate a schematic for hot air ECM. I just need the ses light out so I can smog this pig and procede with my engine swap.