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General information on the JWT ECU upgrade...

Merlin Johnson (

[Editorial note: This FAQ entry has been lifted from the ECU section of the SR20DE page of Merlin's Import Performance Page. Its content has been modified slightly.]

The ECU upgrade requires you to send in yours and probably wait a working week. If you pay for air freight you can get it back in 4 days. The ECU is NOT socketed so you CANNOT return to stock without some trouble. The socketed version applies to the 300ZX cars.

There is no single EPROM to replace as some might think, as there are other support chips to change out. Early versions had a daughter board attached via cable to the main ECU (there is an internal port for this), but left things exposed. Jim Wolf made some changes and now everthing looks stock.

Jim Wolf is the modifier (well actually I think Clark does all the computer work :) of the ECU and does it for Stillen. Right now he is one of the few people in the country that makes a reliable ECU upgrade. I have called Dinan, SuperChip and others and they all don' t have one. [Editorial note: Another ECU has recently surfaced called G-Force. It is mentioned in several FAQ entries below.]

Driving with the new ECU makes power delivery a lot smoother and will pull hard from 4000rpm to 7600rpm with a rev limiter at 7700rpm. Gas mileage doesnt suffer (except under your foot) and this ECU has passed smog. You will have to use 92 octane or better.

The main modifications to the chip are a leaning of mixture at lower RPM (stock runs a bit too rich) adjusting the timing, actually leaning out a bit at upper RPMs, and extending the air/fuel maps. The stock computer will not map out air/fuel past a point and just sticks in the last known ratio, while the new mods will continue to map a/f as long as you keep giving air to the motor, plus your not really going to get above 170hp without the ECU.

Expect about a 8-10 hp increase with no other engine mods. The ECU goes for $695 [Editorial note: Lately, a price of $595 has been floating around the mailing list.]

General information on the G-Force ECU upgrade...

Allen Chan (

The G-Force ECU is sold by G-Force/RPM in Nashua, NH. (603) 594-0763. Ask for Peter or Tedashi there. The biggest problem is that they don't have a core swap option. They are still working on that. The ECU cost about $550, depending on how much arm twisting you do.

Comparisons between the G-Force and JWT ECUs...


At the end of the comparison, Clint and Fred felt that both ECUs performed about the same. They all do what they promised. There was no clear winner. Clint (who was driving with G-Force ECU) noticed that G-Force has a better throtle response in 2nd gear than JWT ECU. And that's when Clint's car would be ahead of Fred's by less than one-quarter of car length. However, Fred's car (JWT ECU) would gain back the distance once he shifted into 3rd and 4th gear. After that they both were dead even.

As for me, the test mule, I like the performance gain I got from G-Force ECU. It definitely out performs stock ECU. Simpily put it, it works! It may not out perform JWT ECU (and vice versa) but it certainly works as well as JWT. I guess it's always good to know that now we have two ECUs to choose from. Assume there won't be any kind of price fixing, we should be able to enjoy competitive pricing soon.

Clint Fong (

As you all may know, Fred and I raced our (otherwise) identically prepped SE-Rs - mine with Tony's G-Force ECU installed in my car, and Fred with his JWT ECU. We both have POP Charger intakes, and HKS exhausts. Tires are BFG Comp T/A HR4s, stock size on stock rims. All in all, I'd say that the GF and JWT ECUs perform similarly. Perhaps the GF has a *slight* edge in initial throttle response, for whatever reasons, but I'd say it's a tough call as to which is definitively least there's now another option for ECUs, which doesn't compromise the standard that was set by JWT :)

Fred Miceli (

The G-Force "seems" to give a slight advantage when we both mashed the throttle in the roll-ons especially in the 2nd gear (40mph +) roll-ons but by the time 3rd winds out, we are dead even and then in 4th I pull just a few feet. However, this is what usually happens when Clint and I normally run (we both have POP, HK$ Exh, JWT ECU). JW ECU and G-Force ECU seem identical, with the G-Force possibly with a very tiny throttle response edge. Again, thats a very very tiny edge...Our tests were as scientific as possible, and we made sure our cars were warmed up, tires warmed up, equal air pressures, etc.

Anyone out there have before and after ECU upgrade track times? How much (in quantitative measurements, like track times) difference did it make?

Merlin Johnson (

Anywhere from .2 to .4 seconds off your 1/4 mile time.

Jay Groesser (

Well, go it in the mail last night and popped it on. I like the way $600 buys you zero instructions, at least installation is obvious. Took it out of the subdivision and gunned it. VROOOOOOOOOM. No shit, you feel a nice kick in the ass. It is DEFINITELY NOTICEABLE!!! Plus I have had a grin for the last 3 hours after seeing the tach rise to the are of 7500rpm!!!

Ok, now for all the skeptics, I knew there would be some of you out there(including me!) that would say it was in my head. So I performed some tests last week, same road, windows up, roof closed. It was atually about 7 degrees cooler the other day. Goes like this:

before ECUafter ecudifference
2nd gear; 2500-6500 rpm
1st run5.67 sec5.33 sec0.34sec
2nd run5.78 sec5.31 sec0.46sec
3rd gear; 2500-6000 rpm
1st run12.21 sec11.28 sec0.93sec
2nd run11.95 sec11.21 sec0.74sec

That was a significant difference in my eyes. Plus I started off same straight road that leads into a curve. On the third gear run w/o ECU, I would hit 6000 about 15 ft before the curve. With ECU I was hitting it nearly 80ft before. I could put the stopwatch down and shift before I even hit the curve.

Is it worth $600 bux? For me, hell yeah. The biggest thing for me is that f*ckin governor is now gone, and which I might add, I will be testing my top speed on the way into Atlanta tonight. The power is very noticeable, mostly on WOT form standstill. Those timed runs didn't fell much quicker except for when I would see how much shorter of a distance it took to get to speed.

Will the ECU upgrades pass smog inspections?

Merlin Johnson (

I have heard from Allen Chan ( that the G-Force ECU did not pass smog. The JWT will pass a smog check, but does not have an EO. (EO is "Exemption Order", just a number that the smog board assigns a product that has gone through the official smog exemption process. To be for real, the product needs one of those numbers.)

I'm thinking about aquiring an ECU. Any drivability improvements noticed? Will the ECU give you any car lengths on competition or is it just improved response?

Pat Griffith (

Before I had the ECU, my best 1/4-mile time was 1...@88.00. After the ECU ugrade (with nothing else done to the car), I went 1...@90.17. To look further inside those numbers, the first time was at 38 degrees and 57 humidity, and the second time was at 70 degrees and 82 humidity. All were done at the same track. And it "felt" faster, too. :)

I just installed my JWT ECU and the car is idling high. Is this normal or should I send it back to JWT?

Lee Alvarez (

Do not worry, I had the same problem, so I called Jim Wolf & spoke with Clark, and he said that it is fairly common, and that after approx. 50 starts the short term memory in the ECU will purge the "bad" info that it has telling it to idle higher. One day you will start the car and without warning the idle will be back to normal, if my memory is correct, it took about 12 days, until mine kicked back down.

I need some honest options! Is the ECU upgrade truly what it's cracked up to be? Is there a big difference between a stock SE-R and one with a ECU? If so, how much should I pay for one and were do I buy it?

Zak Nilsson (

The ECU upgrade truly is what it's cracked up to be. It will give you anywhere between 8 and 12 HP. It will also set your engine up to handle additional mods like headers and cams (cams especially).

There is a big difference between SE-Rs with the ECU and without. Well, noticable, anyway. Let's put it this way; my car is stock and so far every SE-R with an ECU that I've raced or driven has been faster than mine. As in, faster. If you're thinking about getting it, get it. You won't be sorry. How much should you pay and where should you buy it?

There are currently two places I know of to get the SR20DE ECU; Jim Wolf Technology in San Diego (I think) and G-Force Engineering in Nashua, New Hampshire. They are both equivalent, essentially; they both cost about the same. Whichever place you choose, tell them that you're on the SE-R mailing list, then proceed to haggle; you can probably get the price down a bit. The last price I saw for the G-Force ECU was $575.00. Try not to pay any more than that; you can probably get it for less.

I guess it depends on where you live; if you're in the northeast it might be worth your time to drive to N.H. and have them do it while-U-wait. Otherwise you can mail them your board. Same goes for JWT.

Does the new ECU pass for stock or does the Consult (a diagnostic handheld computer that some dealearships use) recognize it as being different?

Allen Chan (

The Consult will recognize an aftermarket ECU. My car got some servicing recently, and the mechanic was asking me about the aftermarket ECU that consult detected.

[Editorial note: Allen has the G-Force ECU.]

Merlin Johnson (

The JWT one will pass for stock.

How does an aftermarket ECU affect Consult readings?

Merlin Johnson (

It shouldn't. If the base idle, and idle advancement is changed then it will show up on the Consult. There is another reading called Alpha, that too can change from spec if you change certain things in the program. On my ECU I have some fuzzy logic built in and I can watch the Alpha reading and see the car learn based on how the percentage reading fluctuates.

I've advanced my timing to 17 degrees per list recommendation. Should I set it back to 15, now that I've got the ECU

Stephen Siat (

Yes, definitely yes. I've talked to Jim Wolf about that and he says there will be too much advance if you leave it at 17. So put it back to 15.

When you plan to install mods such as exhausts, intakes, and the JWT ECU, should you wait to put in the ECU last? Will mods made after the ECU not be picked up by the ECU?

Searl Tate (

You don't need to wait. You can do those mods in any order that you like. When you start to do mods like cams, you want a more custom ECU program to help out with things like smoother idle, etc. Performance won't be affected.

How do you reset the ECU?

Cary Lingg (

To reset the ECU simply disconnect the battery. I believe it takes as little as 20 minutes to reset itself. I usually let it sit disconnected overnight, overkill I guess.

Now why would you want to reset the ECU?

Jui-Lin Hung (

As I understand it, as you drive your car daily, your ECU adjusts according to your driving habits. I figure it also adjusts regarding on how your car performs as well, such as mods. Sometimes, when you make a few changes, your computer is already somewhat adjusted to what you had earlier, and it tries to take into consideration any changes from where it is. When you reset your ECU, you erase all this information, and the ECU can "learn" from scratch.

Ronald S. Chong (

I've had a few friends who've had problem when they installed the intake mod (POP or K&N Filtercharger) for the car. When installed, the car wouldn't idle correctly, but when the stock intake was re-installed, it idled fine. I suggest that they reset the ECU. After they did that, the car idled fine and has done so ever since.

How do I install the ECU in the G20?

Gilbert Callaghan (

[Editorial Note: Installation in the SE-R is essentially the same]

  1. Disconnect the negative end of the battery.
  2. Remove the side panels on both sides of the center console. The driver's side panel is just right of the accelerator. There is a standard phillips screw on the panel towards the rear of the car, and a funky plastic rivet thing on the other end. To remove the rivet, push in the center of it until the center pops in and the rivet will simply fall out. Then the panel can be removed. Do this to the passenger side also.
  3. Just to the right of the accelerator is a big white connector with a (maybe 3/8") hex nut on it. Unscrew the nut and pull the connector off.
  4. Notice that the ECU is mounted with two brackets. The one towards the front, or firewall, does not need to be removed yet, as it will slide out. The one towards the rear can be removed by removing the two bolts that secure the bracket to the floor. (These bolts are also 3/8", or whatever size that nut was.)
  5. Now go to the passenger side and pull the ECU out! The wiring harness is attached to the front mounting bracket so it will move when you pull, so make sure that the wiring harness is not caught on anything.
  6. Once you get the ECU loose, you can remove the front bracket from the ECU by removing two screws, and the ECU (along with the rear bracket) will finally be free.
  7. At this point you may want to test out the new ECU before installing it. Place the new ECU on the passenger side floor and plug it into the large white connector. You MUST screw the nut back on tight before the connector will make a good connection. You don't need to install the ECU in place or ground it, according to Jim Wolf.
  8. Start the car and enjoy! When you're ready to permenantly install it, come back to the next step.
  9. To re-install the ECU, first unscrew the nut and remove the connector.
  10. Now move the rear bracket from the old ECU to the new one.
  11. Next attach the front bracket to the ECU with the two screws.
  12. Slide the new ECU back into it's home, making sure that the wiring harness does not get crimped, and that it ends up on the driver's side of the center console.
  13. Re-attach the rear bracket to the floor with the two bolts.
  14. Screw the connector back on.
  15. Test drive, or at least start the car to make sure all is ok.
  16. Re-install the two side panels. In order to get those funky plastic rivets back on, you have to pull out the center button, insert the rivets, and the push the buttons flush with the rivets.
  17. You're done!

ECU Diagnostic Procedure (transcribed from a '95 200SX SE-R Nissan Factory Shop Manual (with some editorial comments).

Rob Microys (


  • Philips screwdriver (to remove screws on cover)
  • 10 mm socket (to remove 2 nuts holding down both the cover and ECU)
  • Ratcheting socket driver
  • Short extension
  • Universal joint


  1. Remove screws and nuts holding cover down. Take care not to drop in to area behind console, 200SX's are known to eat little nuts and screws, etc, in that area (at least mine does...). Remove cover from ECU, the cover is a little tight around the ECU... don't be afraid to pull hard on it, it won't break.
  2. Turn ignition switch to "ON". Do not start engine
  3. Diagnostic Test Mode I - BULB CHECK
    • Start Engine.
    • Diagnostic Test Mode I - MALFUNCTION WARNING
  4. Turn diagnostic test mode selector on ECM fully clockwise.
  5. Wait at least 2 seconds
  6. Turn diagnostic test mode selector on ECM fully counter clockwise.
  7. Diagnostic Test Mode II - SELF-DIAGNOSTIC RESULTS
    • Start Engine
  8. Turn diagnostic test mode selector on ECM fully clockwise. (Note, This step erases the DTC/MIL, if not, turn test mode selector fully clockwise and repeat step.)
  9. Wait at least 2 seconds
  10. Turn diagnostic test mode selector on ECM fully counter clockwise.
  11. Return to Step 2.


  • In Diagnostic Test Mode II - SELF-DIAGNOSTIC RESULTS (Step 6) the ECU will flash the current DTC on the MIL (malfunction indicator lamp). eg MIL 12 (for Mass Air Flow Sensor) flashes long-pause-short-short-pause, and repeats. MIL 43 flashes long-long-long-long-pause-short-short-short-pause, and repeats.
  • In Diagnostic Test Mode II - FRONT HEATED OXYGEN SENSOR MONITOR, the MIL acts as a primitive Air/Fuel Ratio meter. In closed loop (cruising, light acceleration): ON = LEAN, and OFF = RICH, in open loop (idling, heavy throttle, lift throttle) the light keeps the condition that the light had just before entering open loop.
  • Switching modes is not possible when the engine is running.
  • When ignition switch is turned of during diagnosis, power to the ECM will drop after approx. 1 second and the diagnosis will automatically return to Daignostic Test Mode I.
  • Turn back diagnostic test mode select to the fully counter clockwise position whenever vehicle is in use.


P000055No self diagnostic failure indicated
P010012Mass Air Flow Sen
P011041Int Air Temp Sen
P011513Coolant Temp Sen
P012043Throttle Posi Sen
P012598Coolant Temp Sen
P013037Closed Loop
P013033Front O2 Sensor
P013591FR O2 Sen Heater
P013677Rear O2 Sensor
P017076Fuel Inj System
P030071Random Misfire
P030168Cyl 1 Misfire
P030267Cyl 2 Misfire
P030366Cyl 3 Misfire
P030465Cyl 4 Misfire
P032534Knock Sensor
P033582Crank Pos Sen (OBD)
P034011Camshaft Posi Sen
P040032EGR System
P040236EGRC-BPT Valve
P042072TW Catalyst System
P050014Vehicle Speed Sen
P050525IACV-AAC Valve
P0705103Park/Neut Posi SW
P132021Ign Signal-Primary
P133695Crank P/S (OBD) Cog
P1400105EGRC Solenoid/V
P140135EGR Temp Sensor
P160584A/T Diag Comm Line
P190028Over Heat

Automatic Transmission codes:

P0705111Inhibitor Switch
P0710128Fluid Temp Sensor
P0720112Vhcl Speed Sen A/T
P0725127Engine Speed Sig
P0731113A/T 1st Signal
P0732114A/T 2nd Signal
P0733115A/T 3rd Signal
P0734116A/T 4th Signal
P0740124Tor Conv Clutch Sv
P0745125Line Pressure S/V
P0750118Shift Solenoid/V A
P0755121Shift Solenoid/V B
P1705126Thrtl Posi Sen A/T
P1760123Overrun Clutch S/V

JWT ECU and NOS...

Searl Tate (

The JWT NOS set, I think, is $995 if you already have their ECU. You can buy the JWT ECU _and_ the upgraded program if you want to put together your own NOS kit. Something you should keep in mind is that the cheaper NOS parts are plastic. This means plastic brackets and solenoids. The JWT stuff is the "Pro" grade equipment. I can see everyones point about the price though. It is expensive, but is the best/safest way to do any amount of NOS. Once your system is installed, you want it to be something you don't have to constantly tweak. No manual timing adjustments, no pressing of buttons to release the NOS, etc.

Maintained by Ronald S. Chong (