4AGZE Swap Wiring Info

Okay… this is going to be long, but hopefully it will help you out.

– All references are to the way my ’86 NA (manufactured 8/85) were wired. The references are to the actual plug and pin designation Toyota gives in the electrical wiring diagrams (I have the ’88 one, but not an ’86 one, so there was still a lot of stuff to figure out!). YMMV.

M1 = the gray connector in the engine bay…the side with 12 pins.
M2 = the gray connector in the engine bay…the side with 4 pins.
N1 = the “molex” connector in the trunk that mates to the engine harness.
If I say M1-9, it means M1, pin 9.

– I will use the standard Toyota color code.
B = Black
Br = Brown
G = Green
Gr = Gray
L = Blue
LG = Light Green
O = Orange
P= Pink
R = Red
V = Violet
W = White
Y = Yellow

If the wire is striped, the first letter indicates the basic color of the wire and the second indicates the color of the stripe. Ex: B-W would be a black wire with a white stripe.

– There will be some duplication, as I’ll go through each plug separately and if a wire was on one plug, it will be referenced again on another plug, if it went there.

– I was modifying my ’86 body’s electrical harness to mate to the ’88’s engine harness.

– The car hasn’t been cranked, yet…the motor is still on the ground, so I can’t claim victory, yet. But I’m supremely confident (I guess!) it will work. It MUST work!
First off, I wanted to eliminate my ECT connector, since my car has always been (and always will be) a manual tranny. So, I uncoiled the ECT connector Toyota so thoughtfully put in there and did the following to the respective pins:

1. B “IDL” This goes to M1-9. I clipped it. It was simply being routed back to the ECT. The real magic is still happening between the TPS and the ECU via the engine harness.

2. Y-R “L3”. Goes to ECU, N1-19. Remove.

3. Y-G “L2”. Goes to ECU, N1-14. Remove.

4. Y-L “L1”. Goes to ECU, N1-9. Remove.

5. G-O. “OD2” Goes to passenger cabin G2-11, driver’s side kick panel. Can remove…but I kept this wire and used it (since it was already run for me) for my Reg/Prem fuel select switch. It turned from G-O to R in the trunk and was routed to N1-5. (Yeah, I know…there’s still a wire in N1-5. We’ll get to that later.)

6. G-B. “Prk” according to the 88 wiring diagram. Wasn’t there on my car.

7. L. “N”. Went to a spade connector in my trunk. Removed.

8. L-Y. “Pwr”. Went to G2-5 under the driver’s kick panel. Can be removed, but I used it since it was already run for me. It became the wire for my Air/Fuel Ratio gauge and connects to the oxygen sensor line on the ECU.

9. Had no connection.

10. L-Y. “S3”. Went to M1-8. Remove.

11. Br-Y. “S2”. Went to M1-7. Remove.

12. V. “S1”. Went to M1-6. Remove.

13. Br-B. “DG”. Went to N1-16. Remove.

14. Not connected.

15. LG. “SPD2”. Went to N1-1. Remove.

16. V-W. “SPD1”. Also goes to Cruise computer and N1-10. Clip this wire where it joins the others and seal it with brush-on electrical tape or something.

17. P-W. “OD1”. Clip from Cruise connector, pin 6.

18. Not Connected.

19. W-B. “Gnd”. Clip from wire bundle in trunk.

20. LG. “L”. Went to M1-3. Remove.

21. LR-R. “S”. Went to N1-3. Remove.

22. G-W. “STP” or “BRAKE” depending on which diagram you look at. Clip from where it bundles to other G-W wires in the trunk and seal.

23. W-R. “+B”. Went to two other wires under the fuse box in the engine compartment. Clip there.

24. B-Y. “IG”. Clip from where it connects to other wires in the trunk.

That completes removal of the ECT connector. The cruise connector stays. Next up I’ll discuss the M1 and M2 (gray) connectors in the engine bay….

Okay, first off, M2 (the one with four pins) stays as is.

M1 had some changes…a lot have been discussed already. At this point there are only a few wires left on it, but I’ll hit all twelve pins, anyway.

1. B-W. This one gives you +12V to your starter only if you have an automatic tranny…and only when your key is in the “Start” position. Disconnect or leave. I used this pre-existing line, though. I disconnected it from the Blue connector (sorry…don’t know the pin number, but it was the third pin up from the bottom left of the connector, if I remember correctly). Anyway, I used this one to run my SC light. I connected a R-W wire to this one, just under the fuse box and ran it to N1-9.

2. B-W. Disconnect and connect to the wire that is currently at M1-4. This wire provides +12V when the clutch is pressed and the key is in the “Start” position. It energizes the Starter relay to route +12V out M2-4 to the starter, etc.

3. LG. “L” from ECT-20. Clip it.

4. B-W. Disconnect and wire directly to the wire that WAS at M1-2. This is the wire that actually goes to the hot side of the starter relay in the fuse box.

5. G-W. “Ck Engine Light”. This needs to be extended into the trunk to go to N1-1.

6. V. “S1” from ECT-12. Clip it.

7. Br-Y. “S2” from ECT-11. Clip it.

8. L-Y. “S3” from ECT-10. Clip it.

9. B. “IDL” from ECT. Clip it.

10. P-W. “OD1”. Came from ECT-17 and Cruise-6. Remove.

11. B-W. I believe this is supposed to come from N1-16 (in the trunk) as the “A/C” signal to the A/C Amplifier. I don’t have A/C on this car…never will, but see the discussion of N1-16 to see how I used this wire.

12. L-W. I believe this is the signal from the cooling fan computer wire. I hooked it to N1-11.

I guess I should discuss the JSpec GZE clip that has two wires on M1 at pins 10 and 11. According to the 88 EWD, these supposedly have something to do with the A/C Lock Sensor. I used a couple of wires I removed earlier, LG and LG-R from another harness to actually put in M1 to mate up with these, just in case they turn out to be something different. I routed them into the passenger cabin behind the seat the coiled them up there with a piece of masking tape to explain what they are, should future generations need to know.
Next up, the N1 trunk connector that mates to the JSpec GZE engine harness!

Alright….now the N1 connector that actually mates with the engine harness. If you’ve followed the posts previous to this, there are already several pins removed and already explained, but I’ll briefly cover those again, in the spirit of full disclosure for every pin.

1. G-W. “WAN” or “Ck Engine Light”. M1-5 was extended to here.

2. Same as 86. Stays. Y-B. Oil pressure sender.

3. G-W. “Brake” for CHMSL (Center High-Mounted Stop Light). My ’86 has a separate connector already wired up for the spoiler light, so I left this empty. (It was removed previously from the ECT connector removal.)

4. B-W. To Injectors. Big changes here. The ’86 has the EFI Injector resistor mounted behind the battery bracket. They then route a black wire to this pin, which feeds injectors 3 & 4 on the NA and a red wire to pin 5 to feed injectors 1 & 2. The ’88 puts the injector resistor on the engine harness and only requires one wire to feed it through this connector. The wire on this pin needs to connect to the injector relay, pin 4, in the engine bay fuse box.

5. R. “Reg/Prem”. Gas selector switch in the dash board provides this signal. I used the wire left behind from pin 5 on the ECT removal and tapped this R wire to it. See the discussion on pin 4, above. This WAS the connection for the signal to injectors 3 & 4.

6. Same as 86. Stays. Y-G. Water temp sender.

7. Same as 86. Stays. B. EFI Main Relay.

8. Same as 86. Stays. B-Y. 10A Engine Fuse.

9. R-W. “TIL”. This is the SC light signal. I connected it to what was connected at M1-1, since that runs all the way to the driver’s kick panel and will be a breeze to wire from there.

10. Same as 86. Stays. V-W. Speed Sensor.

11. L-W. Cooling Fan Computer signal. Wired to the wire that was at M1-12. I’ve not confirmed this is the correct wire. Still need to find out about this one.

12. Same as 86. Stays. B-R. Engine Main Relay to Coil.

13. Same as 86. Stays. W-R. Battery AM2 Fuse.

14. Not used. Was removed when disconnecting the ECT connector.

15. Same as 86. Stays. B. To igniter and tach.

16. B-W. “A/C” signal from A/C Amplifier. I hooked this to the B-W wire that was at M1-11 before and disconnected it from this connector. I then extended the wire and routed it back into the engine bay to use as a control ground for my SPAL fan. The wire by the kick panel was extended up to the right side of the gauge cluster housing, where I replaced the switch blank there with a spare defroster switch to control the SPAL fan. See the discussion for M1-11 in the previous post.

17. Same as 86. Stays. Y. IC Regulator.

18. Same as 86. Stays. L. Fuel Pump.

19. G-W. “Stop”. I jumpered this to the separate spoiler brake light harness which is very nearby and accessible. You’ll remember that the Y-R wire that was here was removed with the ECT connector.

20. Same as 86. Stays. B-G. “IG2”

21. Same as 86. Stays. W-B. Ground to seatbelt warning relay.

22. Same as 86. Stays. B. “V-ISC”. Idle up VSV signal.

Hope that helps somebody. It’s correct AFAIK for my particular car. I’ve talked to somebody else that had an ’86 with no power anything and he didn’t have hardly any pins on M1. I figured that they would have used the same harness on every ’86, so YMMV, even if you have an ’86!

This documentation in no way replaces the Toyota MR2 Repair Manuals. The purpose of this content is only to provide supplementary information to fellow MR2 enthusiasts. Midship Runabout and its contributing authors will not be held responsible for any injury or damages that may occur as the result of practicing any of the methods or procedures described within this website. Article and photo submissions are property of the contributing author.

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