ECU Indentification
       
       
A31  MEC-R282A         
A31  RB20DE AT FR   23710-72L00 MEC-R100 ?? 27C128 27C128       
A31  RB20DET AT FR  23710-73L10 MEC-R103 ?? 27C128 27C128       
A31  RB20DET MT 4W  23710-86L00 MEC-R204 ?? 27C256 27C256       
A31                 23710-0A511 MEC-R123 ?? 27C128 27C128       
A31 RB20DET AT FR   23710-5L210 MEC-R330 ?? 27C256 27C256       
A31 RB20DET AT FR   23710-73L70 MEC-R203 B ?? 27C256 27C256       
A31 RB20DET MT FR   23710-0A502 MEC-R222 ?? 27C256 27C256       
A31 RB20DET MT FR   23710-73L00 MEC-R102 ?? 27C128 27C128       
A31 RB20E AT FR     23710-71L10 L170CDA5 ?? 27C256 27C256       

C32  RB20DET AT FR  23710-94L10 MEC-R113 ?? 27C128 27C128       
C32  RB20DET FR     23710-45L71 MEC-R51 ?? 27C128 27C128       
C32  VG20ET AT FR   23710-43L13 MEC-542R *2 ?? 27C128 27C128       
C32  VG20ET AT FR   23710-43L72 MEC-V52R ?? 27C128 27C128       
C33  RB20DE AT FD   23710-72L70 MEC-R201 ?? 27C256 27C256       
C33  RB20DE AT FR   23710-5L110 MEC-R310 ?? 27C256 27C256       
C33  RB20DET AT FR  23710-73L70 MEC-R203 ?? 27C256 27C256       
C34  RB20DE 5AT FR  23710-74T01 ?? H8/534        
C34  RB25DE 5AT FR  23710-75T02 ?? H8/534 H8       

DR30  FJ20ET MT FR 23710-R2200 MEC-250Y ?? 27C64 27C64       
DR30  FJ20ET MT FR 23710-R2205 2521 ?? 27C64 27C64       
HR30  L20ET MT FR 23710-15S00 A18-000 ?? 27C64 27C64       

HR31  RB20DET AT FR 23710-59S13 MEC-R17 ?? 27C128 27C128       
HR31  RB20DET MT FR 23710- MEC-R42 ?? 27C128 27C128       
HR31  RB20DET MT FR 23710-59S03 MEC-R16 ?? 27C128 27C128       
HR31  RB20DET MT FR 23710-59S04 MEC-R24A ?? 27C128 27C128       

R30  FJ20E MT FR 23710-R2000 A18-000 ?? 27C64 27C64       
R30  FJ20E MT FR 23710-R2200 ?? 27C64 27C64       
R30  FJ20ET MT FR 23710-2210 ?? 8K 8K       
R30  FJ20ET MT FR 23710-2210 ?? 8K 8K       
R30  FJ20ET MT FR 23710-R2202 052 ?? 8K 8K       
R30  FJ20ET MT FR 23710-R2203 2510 ?? 8K 8K       
R30  L20ET MT FR 23710-15S00 A18-000 ?? 27C64 27C64       
R30  L20ET MT FR 23710-15S01 J136BDM1 ?? 8K 8K       

R31 GTS-R RB20DET MT FR 23710-70S01 MEC-R46 27C128
R31 1988 RB20DE       23710-72L10 MEC R-101   (#63)
R31     RB20DE AT FR  23710-58S13 MEC-R23A 27C128
R31     RB20DE MT FR  23710-58S03 MEC-R22  27C128
R31     RB20DET AT FR 23710-80S11 MEC-R43  27C128
R31     RB20DET MT FR 23710-59S05 MEC-R26  27C128
R31     RB20DET MT FR 23710-79S02 MEC-R70R 27C128
R31     RB20DET MT FR 23710-80S02 MEC-R47  27C128
R31     RB20DET MT FR 23710-80S03 MEC-R72  27C128
R31     RB20E AT FR   23710-91S11 J170BDA3 27C128
R31    RB20E         23710-91L60?? A11-000 L14?? (#AY)
R31     RB20ET MT FR  23710-76S00 J171BDM3 27C128
              27310-73L60 Mec-R202 B 0X05  (#76)

R32-GTE   RB20E    Auto FR     23710-02U10 A11-000J01 (preFL, no ABS no HICAS)
R32-GTR   RB26DETT Manual 4W   23710-05U02 MEC-R128 27C256
R32-GTR   RB26DETT Manual 4W   23710-05U60 MEC-R280 27C256
R32-GTS   RB20DE               23710-01U11 MEC-R125 1 ox05 (#21)
R32-GTS   RB20DE   Manual      23710-10U00 MEC-R210 B 2701 (#BE)
R32-GTS   RB20DE   Auto        23710-10U11 MEC-R217 3415 (#BF)
R32-GTS   RB20DE   Manual MT   23710-01U00 MEC-R104 27C256
R32-GTS   RB20DE   Auto FR     23710-01U11 MEC-R125 (preFLno ABS no HICAS)
R32-GTS25 RB25DE   Manual FR   23710-08U01 MEC-R232 27C256
R32-GTS25 RB25DE   Auto FR     23710-08U11 MEC-R233 (facelift, no ABS no HICAS)
R32-GTS4  RB20DET  Auto 4W     23710-04U70 MEC-R117 27C256
R32-GTS4  RB20DET  Manual 4W   23710-04U60 MEC-R116 27C256
R32-GTSt  RB20DET              23710-01U00 MEC-R120        (#BE)
R32-GTSt  RB20DET              23710-0A900 MEC-R235 27C256
R32-GTSt  RB20DET  Auto FR     23710-04U11 MEC-R109 27C256
R32-GTSt  RB20DET  Auto FR     23710-04U12 MEC-R127 27C256  (#23)
R32-GTSt  RB20DET  Auto FR     23710-11U10 MEC-R213 B 3510  (#BJ)
R32-GTSt  RB20DET  Manual FR   23710-04U00 MEC-R106 27C256
R32-GTSt  RB20DET  Manual FR   23710-04U01 MEC-R126 27C256   (#22)   
R32-GtSt  RB20DET  Manual M FR 23710-04U02 MEC-R132 27C256
R32-GtS   RB20DE   Manual M FR 23710-11U00 MEC-R212 B 3603 (#BH)
R32-GtS   RB20DE   Manual M FR 23710-11U10 MEC-RZ17 B 1Z17 (#BJ)  (ASB)
R32              Type-M Manual 2371M 04U02 MEC-R132R 3613              


R33  GTS    RB20DE?? Auto FR             23710-15U10 27C256
R33  GTS25  RB25DE   Auto FR             23710-17U11 MEC-R511 H8 534
R33  GTS25  RB25DE   Manual FR           23710-17U00 H8/534
R33  GTS25  RB25DE   AUTO                2371M-17U15 MEC-R515R (9903)
R33  GTS25t RB25DET           Auto 4WD   23710-21U70 MEC-R630 H8 534
R33  GTS25t RB25DET          Auto 2WD     23710-08U11 MEC-R233 1X25 (#BB)
R33  GTS25t RB25DET  Series 1 Manual FR  23710-21U00 MEC-R520B H8 534
R33  GTS25t RB25DET  Series 1 Auto       23710-21U11 MEC-R531 A1 3Y24  (#TK)         
R33  GTS25t RB25DET  Series 2 Auto?      23710-21U11 MEC-R531 A1 3904         
R33  GTS25t RB25DET  Series 2 Auto?      23710-21U11 MEC-R531 A1 3X08  (#TK)
R33  GTS25  RB25DE   Series 2 Manual 4WD 23710-21U60 MEC-R620 A3 5830  (#CC)
R33  GTS25t RB25DET  Series 2 Manual RWD 23710 13U01 MEC-R721 A1 6913
R33  GTS25t RB25DET  Series 2 Manual RWD 23710 13U01 MEC-R721 A1 7207  (#G8)
R33  GTS25t RB25DET           Auto   RWD 23710 13U10                (#G9)
R33  GTR V-Spec RB26DETT                 23710 24U01 MEC-R581 A1 8625  
   
RS13 180SX CA18DET AT FR 23710-36F15 MEC-D017  27C128 27C128       
RS13 180SX CA18DET MT FR 23710-36F05 MEC-D016 ?? 27C128 27C128       

S12 CA18DET AT FR 23710-31F10 G121BDA2 ?? 27C128 27C128       
S12 CA18DET MT FR 23710-30F01 MEC-451 ?? 27C128 27C128       
S12 CA18ET MT FR 23710-05F04 ?? 27C64 27C64       
S12 CA18ET MT FR 23710-31F00 G121BDM2 ?? 27C128 27C128       
S12 FJ20E FR     23710-R2011 ?? 8K 8K       
S13 180SX  SR20DET MT SR 23710-50F05 K170SDM3 ?????? 27C256 M6M7256       
S13 CA18DE AT FR 23710-35F11 MEC-D014 ?? 27C128 27C128       
S13 CA18DE MT FR 23710-35F00 MEC-D001 ?? 27C128 27C128       
S13 CA18DET AT FR 23710-36F11 MEC-D015 27C128 27C128       
S13 CA18DET MT FR 23710-36F00 MEC-D003 ?? 27C128 27C128       
S13 SR20DE AT FR 23710-52F10 K078PDA7 ?????? 27C256 M5M7256       
S13 SR20DE MT FR 23710-52F00 K078PDM7 ?????? 27C256 M5M7256       
S13 SR20DET AT FR 23710-50F10 K078ODA8 ?????? 27C256 M5M7256       
S13 SR20DET MT FR 23710-50F00 K078ODM8 ?????? 27C256 M5M7256       
S14 SR20DE MT FR 23710-65F00 ??????? 27C256 37791E       
S14 SR20DET AT FR 23710-69F10 K134XDA8 ??????? 27C256 M5M7512       
S14 SR20DET MT FR 23710-69F00 ??????? 27C256 M5M7256       
SR18DE AT FF 23710-58Y12 S069PDA1 ?? 27C256 27C256       
SR18DE MT FF 23710-58Y01 S069PDM9 ?? 27C256 27C256       
SR20DE MT FF 23710-78N00 W077HDM5 ?????? 27C256 27C256       
SR20DET 23710-95N11 W184LXDZ5 ?????? 27C256 M6M7256       
Y30 VG30ET AT FR 23710-V7514 MEC-V13 ?? 27C128 27C128       
Y30 VG30ET AT FR 23710-V7516 MEC-V19R ?? 27C128 27C128       
Y31 VG30DET AT FR 23710-45V71 MEC-E09 ?? 27C128 27C128       
Y31 VG30DET AT FR 23710-45V72 MEC-E14 ?? 27C128 27C128       
Y31 VG30DET AT FR 23710-71V70 MEC-E102 ?? 27C256 27C256       
Y31 VG30DET AT FR 23710-71V72 MEC-E108 ?? 27C256 27C256       
Y31 VG30E AT FR 23710-64V11 MEC-V106 ?? 27C256 27C256       
Y32 VG30DE AT FR 23710-OP510 MEC-E207 ?? 27C256 27C256       
Y32 VH41DE AT FR 23710-1P122 8XD1112J ?? 27C256 27C256       
Z31  RB20DET MT FR 23710-20P60 MEC-R60C ?? 27C128 27C128       
Z31  RB20DET MT FR 23710-20P61 MEC-R62 ?? 27C128 27C128       
Z31  VG20ET AT FR 23710-12P11 20A3 ?? 8K 8K       
Z31  VG20ET AT FR 23710-12P11 20A4 ?? 8K 8K       
Z31  VG20ET MT FR 23710-12P01 20M3 ?? 8K 8K       
Z31  VG20ET MT FR 23710-12P01 20M4 ?? 8K 8K       
Z31  VG30DE MT FR 23710-22P01 MEC-E12 ?? 27C128 27C128       
Z31  VG30ET AT FR 23710-15P10 ?? 8K 8K       
Z31  VG30ET AT FR 23710-22P72 M156DDA4 ?? 27C128 27C128       
Z31  VG30ET AT FR 23710-V5312 V5312-1 ?? 8K 8K       
Z31  VG30ET MT FR 23710-15P00 4302 ?? 8K 8K       
Z31 RB20DET MT FR 23710-20P01 MEC-R15E ?? 27C128 27C128       
Z32  VG30DE AT FR 23710-40P11 M157BDA4 ?? 27C256 27C256       
Z32  VG30DE MT FR 23710-40P00 M157BDM3 ?? 27C256 27C256       
Z32  VG30DE MT FR 23710-40P01 8AB9119J ?? 27C256 27C256       
Z32  VG30DETT AT FR 23710-41P12 M105ADA5 ?? 27C256 27C256       
Z32  VG30DETT AT FR 23710-41P13 M105ADA6 ?? 27C256 27C256       
Z32  VG30DETT AT FR 23710-48P76        
Z32  VG30DETT MT FR 23710-41P00 M105ADM4 ?? 27C256 27C256       
Z32  VG30DETT MT FR 23710-41P01 M105ADM5 ?? 27C256 27C256       
Z32  VG30DETT MT FR 23710-41P03 M105ADM6 ?? 27C256 27C256       
Z32  VG30DETT MT FR 23710-41P04 8AB9121J ?? 27C256 27C256       
Z32  VG30DETT MT FR 23710-51P60 6AK8915J1 ??????? 27C256 M5M       
    

If i may draw some conclusions:
"23710-xxxyz"
Where 23710 appears to be the generic partnumber for "ECU"
"xxx" is the engine/chassis combo code.
GTRs are 05U
RB25 are 08U
RB2oDE are 01U
RB20DET are O4U
Some exceptions here - maybe M-spec, Type X / Type S differences? But surely they use
the same engine block as the normal ones.
This reminds me of the old "IDing GTR engine blocks" thread. 05U is factory,
there are also 24U, O46 numbers that I have heard rumored is for GrpA / N1 blocks?

"y" is gearbox
    0 = manual RWD
        1 = auto RWD
        6= manual 4WD
        7= auto 4WD.

"z" is a mystery to me. Hard to tell exactly what.
Not ABS/HICAS/ facelift, as my examples point out
(all 100% as I read the ECUs last night and know the spec of the cars).
One GTR code has a 2, the other has a 0.

As far as I know MEC-R213 refers to the chip, as it's stamped next to chip on the
circuit board and has lines from MEC-R213, going towards where chip is mounted.
Not sure what the numbers mean after it, but could be related to the chip.