280ZX Turbo to Z31 Turbo ECU and MAF Upgrade

Which Z31 Turbo ECU?

Any Z31 Turbo ECU will work. It just has to match two things on your car: the injector impedance and the O2 sensor type. The 280ZX Turbo runs low-impedance injectors and a one-wire zirconium O2 sensor.

• High-impedance ECU with low-impedance injectors: add six dropping resistors (see Dropping Resistors) or switch to high-impedance injectors.
• Low-impedance ECU with high-impedance injectors: works normally.
• O2 sensor: titania and zirconium sensors aren't interchangeable. Use the type your ECU was built for.

The full chart, with O2 sensor part numbers, is on Z31 ECU, Injector and O2 Sensor Differences. See also 280ZX ECU Differences.

Parts Needed

• Any year Z31 MAF. Yellow sticker = Federal, blue sticker = California.
• A Z31 Turbo ECU that matches your injectors and O2 sensor (see the table above).
• Any year Z31 ECU and MAF plugs. The California MAF has only 5 pins.
• Any year VG30E(T) or VG33E distributor encoder disc (chopper wheel). It's a good idea to use its matching CAS (crank angle sensor) too, since the 280ZXT's is only gel covered.
• Several spools of automotive wire, a soldering kit, heat shrink and electrical tape.
• 1986–89 ECU: a heated titania O2 sensor.
• 1988–89 ECU: six dropping resistors (6.8 ohm, 10 watt). A 1981 Turbo already has a resistor pack.
• 1981 Turbo: the 1982–83 Turbo distributor and shaft.

Procedure

Wire colors: B = black, G = green, L = blue, R = red, W = white, Y = yellow. The first letter is the main color and the second is the stripe, so Y/L is yellow with a blue stripe.

ECU Plugs: Pins to Change

Connecting the ECU

1. Insert a new wire (from a Z31 ECU plug) into the empty pin 12 position of the ECU connector. Cut wire 33 Y/L, leaving several inches, and attach it to the new pin 12. Pin 12 now connects through wire 33 Y/L to the 12 R/W wire on the MAF (position F), so the ECU can run the MAF's self-cleaning cycle. Z31T ECU pin 33 isn't used; tape it off.
2. Insert a new wire into the empty pin 34 position and connect it to switched 12V power (27/35 B/W from the fuel pump control module sub harness).
3. 1981 Turbo only: insert a new wire into the empty pin 114 position and connect it to fused direct battery power.

Connecting the Air Regulator

The 280ZXT ECU controls the air regulator through pin 108 B, but on the Z31T ECU pin 108 runs the fuel pump relay, so the two wires trade places.

1. Cut the 108 B and 16 L/R wires coming out of the ECU connectors, leaving several inches of wire.
2. Connect the harness side of 108 to ECU pin 16. The Z31T ECU now controls the air regulator from pin 16.

Connecting the Fuel Pump Relay (FPR)

1. Connect the remaining harness side of 16 L/R (the 12V+ that turns on the relay) to switched 12V power (27/35 B/W from the fuel pump control module sub harness).
2. Remove the glove box and find the green FPR with a flashlight (removing the dash may be easier). Cut the black wire (the relay's ground) before the FPR and connect the relay side to a new wire. Run the new wire under the dash to ECU pin 108 (cut in the step above). The Z31T ECU now controls the FPR ground from pin 108.

Connecting the MAF

1. MAF position A, wire 30 Y/G → 30 Y/B on the 280ZXT harness.
2. MAF position B, wire 31 B → 31 Y/R on the harness.
3. MAF position C, wire B → body ground.
4. MAF position D, wire 26 B → 26 B on the harness.
5. MAF position E → run a new wire to 27/35 B/W (the VCM solenoid power source, under the AFM bracket).
6. MAF position F, wire 12 R/W (cleaning cycle) → 33 Y/L on the harness.

MAF self-cleaning: about 5 seconds after you turn the key off, the ECU heats the MAF hot wire to roughly 1,000°C (1,832°F) for 1 second to burn off dust. It skips the cycle if the engine never went above 1,500 rpm, the car never went above 20 km/h (12 mph), the head temperature is over 115°C (239°F), or the engine stalled with the key on. A short glow at the MAF after shutdown is normal.

Fuel Pump Control Module (1982–83 Turbo)

The Z31T ECU doesn't use a fuel pump control module; it controls the FPR ground itself. Remove the FPCM and tape up its connector. The 1981 Turbo doesn't have an FPCM.

AAC and EGR Controls

The Z31T ECU uses different AAC and EGR systems. You can leave the 280ZXT actuators on the manifold, but they won't work. Remove the VCM solenoid and cap any open vacuum lines. If you remove the AAC actuator, adjust the throttle body stop screw to set idle speed.

Knock (Detonation) Sensor

The Z31T ECU expects a different knock sensor signal. Disconnect the sensor wiring on the right side of the block, by the oil filter, and tape it up.

Distributor Encoder Disc and CAS

1. Remove the distributor cap, then the rotor.
2. Under the rotor is a Phillips/flathead screw. Press down firmly with the right screwdriver and remove it.
3. Remove the rotor mount, then the 280ZXT encoder disc.
4. Install the VG30/VG33 disc in reverse order, number stamp up.
5. 1981 Turbo: swap in the 1982–83 Turbo distributor and shaft first.

If you use the VG CAS, its plug doesn't match the L28ET harness. The VG CAS pigtail can be found on Pathfinders, Quests and Villagers up to 1996. Wire it as follows:

• Black to black (ground)
• Green to green/yellow (ECU pin 8, 1° signal)
• Red to green/black (ECU pin 17, 120° signal)
• Black/white to black/white (12V)

Dropping Resistors

1981 Turbo with a 1984–87 ECU: remove the resistor pack

Either make a set of 6-to-1 spade jumpers to fit the resistor plug, or cut out the plug and connect all 7 wires together (1 power + 6 injectors). Do not bypass the resistors if you're using a 1988–89 ECU.

1988–89 ECU: add resistors

If you keep the stock low-impedance injectors with a 1988–89 ECU, add a 6.8 ohm, 10 watt resistor inline with the power wire to each injector. Stagger them along the harness so they don't make a bulge.

O2 Sensor

Match the sensor to the ECU. The 1984–85 ECU uses the stock one-wire zirconium sensor. The 1986–89 ECU needs a heated three-wire titania sensor (NGK 24007 was the one used in the guide). The titania sensor has a 12 mm thread, so use an 18 mm to 12 mm adapter or weld in a new M12x1.25 bung.

1. Black (signal) wire → ECU pin 24.
2. Red heater wire → switched 12V power.
3. White heater wire → ECU pin 115.

ECU Pin Comparison by Year

Highlighted rows are the pins you add or change.