K-series JDM PRC / PRD / PRB ECU info

When it comes to K-swapping, the ECU becomes a pretty big deal. If you don’t have the funds for an engine management system right off the bat, you have to consider running a stock ECU for the time being. You also need to run the correct ECU for the respective K engine and transmission you’re using or else you’re going to run into specific issues related to programming and possible poor running conditions due to differences in: VTC maps, fuel & timing maps, AFR, immobilizer system, speed sensor type, and reverse lock-out functionality, to name a few.

Because there are various eco and performance K-series engines, I’m going to focus this article on the common performance based K20A engine, specifically, the JDM K20A Type-R engine from the 01-05 EP3 CTR + 01-06 DC5 RSX Type R and USDM K20A2/K20Z1 engine from the 02-06 USDM DC5 RSX Type-S. I won’t be focusing on the 06+ Civic FA/FD generation ECU’s because Honda completely changed the physical ECU design and programming architecture design on these generation ECU’s due to them switching to a drive-by-wire throttle system.

The JDM 01-05 EP3 CTR “PRD” and 01-06 RSX Tye-R “PRC” JDM ECU’s are very handy for golden era Kswaps and K-series era car Kswaps (EM2/EP3/DC5) in their stock form as they do not have a factory programmed immobilizer in them, unlike the USDM 02-04/05-06 RSX Type-S “PRB” ECU. When using a stock USDM PRB ECU in golden era or mentioned K-series era car, you MUST buy an immobilizer bypass box that K-Tuned and Hybrid Racing offer in order to have fuel pump operation – no way around it. For K-series era cars (EM2/EP3/DC5), you can have the immobilizer reprogrammed  at the dealership if you don’t want to fork money out for a bypass box, but doing this can tend to cost more than going with a bypass box. This bypass box tends to fall in the $150-$175 range. The beauty of the JDM ECU is that it saves you money on the immobilizer bypassing hassle, money you can use towards getting the ECU KPRO’d later on or money used towards a whole different engine management system altogether such as FuelTech, Link, etc..

There are some slight differences with these ECU’s wiring pinouts, specifically at the fuel pump relay pinout.  So, if you try using a JDM ECU in a USDM K-swapped vehicle or USDM K-series native vehicle as is, the car will not start. To fix this, the fuel pump relay pinout needs to be moved from ECU pin E1 down to pin E10. E10 is the proper pinout on the JDM PRC/PRD ECU’s for the FPR.
Pro Tip: get a donor terminal pin with about 1-2″ of wire lead pinned to E10 and then splice it to the E1 wire. Doing this kills 2 birds with one stone, as you will never have to worry about  the FPR pinout again if you ever find yourself switching between USDM and JDM ECU’s for whatever reason!

JDM vs USDM PRD/PRC/PRB ECU DIFFERENCES

• FUEL PUMP RELAY
  PRC/PRD – Uses FPR pinout E10
  PRB – Uses FPR pinout E1
• IMMOBILIZER SYSTEM
  PRC/PRD (01-04) – absent
  PRC  (05) – present
  PRB (02-06) – present
• VTC MAPS
  PRC/PRD – programmed for K20A Type-R camshafts and PRC intake manifold (large intake runners)
  PRB (02-04) – programmed for K20A2 camshafts (weaker profile than R cams) and PRB intake manifold (smaller intake runners)
  PRB (05-06) – programmed for K20Z1 camshafts (shares same cam profiles as JDM Type-R cams but with a PRB intake manifold)
• FUEL & TIMING MAPS
  PRC/PRD –  programmed for premium higher octane rated fuel (higher than 93)
  PRB – programmed for US rated octane fuel (91-93)
• FUEL INJECTORS
  PRC/PRD/PRB – all programmed for 310cc injectors use
• OXYGEN SENSORS
  PRC/PRD/PRB – all programmed with dual 02 sensor configuration ie. wideband primary 02 (upstream) and narrowband secondary 02 (downstream)
• SPEED SENSOR – VSS / CSS
  PRC/PRD (01-05/06) – programmed for low frequency VSS type speed sensor (mechanical style, mounted on rear side of trans)
  PRB (02-04) – programmed for low frequency VSS type speed sensor (mechanical style, mounted on rear side of trans)
  PRB (05-06) – programmed for high frequency CSS (located on front side of trans)
• SPEED LIMITER
  PRC/PRD – set somewhere between 110-120mph
  PRB – no speed limiter
• VTEC PRESSURE SWITCH SENSOR
  PRC/PRD – not present
  PRB – present / enabled
• VTEC CROSSOVER POINT
  PRC/PRD – programmed very high, around 6000-6200rpm
  PRB – programmed around 5700rpm
• REVERSE LOCK OUT
  PRC/PRD/PRB – all programmed for reverse lockout functionality, typical for a 6MT ECU.

Because the JDM 01-05 K20A Type-R and USDM K20A2/K20Z1 engines are very similar (aside from slight cam profile and compression ratio differences), you can get away with using a JDM PRD/PRC ECU on a USDM K20A2/Z1 engine and vice-versa for a period of time. It’s HIGHLY SUGGESTED to upgrade your ECU whether it be Hondata KPRO’d or you switch to FuelTech/Link/etc. system so that its programmable so that you can get FULLY TUNED!