V4

48-pin table

Sorted TunerStudio 1–48. Molex ID is the cavity on the housing.

01 Power, grounds & main relay

The V4 will not run from key-on voltage alone. L4 (pin 5) wakes it, E4 (pin 29) latches the main relay, M4 (pin 1) is the resulting 12 V feed.

How the latch works

On key-on the ECU grounds E4, the relay closes, M4 comes alive, and firmware holds the relay until it has finished writing to flash on shutdown. E4 is not a TunerStudio-assignable output.

Pins: L4 · 5 · Key-on 12 VE4 · 29 · Main relay controlM4 · 1 · 12 V from main relayM3 · 2 · Power groundL3 · 6 · Power ground

Relay pinout (standard 5-pin automotive)

• 30 — constant battery 12 V, fused 25–30 A close to the battery.
• 87 — switched 12 V out to M4, injectors, coils, VVT, idle, sensor 12 V if used.
• 86 — relay coil to ignition-switched 12 V (same feed as L4 is fine).
• 85 — relay coil to ECU E4 (low-side).
• 87a — unused.

Grounds

M3 and L3 are power ground. Run both, 2.0 mm² or thicker, to a sanded boss on the block or heads — not a painted seat-belt bolt. H4 and G4 are analog ground. Sensor grounds stay in that star and only meet chassis inside the ECU.

Minimum fuse map

• Battery → relay 30: 25–30 A.
• Key-on → L4 and relay 86: 5 A.
• Relay 87 → injectors / injector driver: 10 A (4-cyl) to 20 A (8-cyl batch).
• Relay 87 → coil +12 V: 10–15 A.
• Fuel pump (via D2 relay): 15–20 A on the pump side, 5 A on the coil side.

02 Analog sensors

Four thermistor inputs with pull-ups, ten 0–5 V analog channels, two independent 5 V supplies, two analog grounds. Auxiliary reuse pins are analog inputs. Sensor roles are assignable in TunerStudio.

Temperature

H3 (CLT) and G2 (IAT) are the usual pair. G3 and G1 are extra thermistor / Hall / flex pins — oil temp, flex fuel, VSS, or a spare sender. On-board pull-ups. Two-wire NTC: one side to the analog pin, the other to sensor ground (H4 or G4).

Pins: H3 · 18 · CLTG2 · 23 · IATG3 · 22 · AN temp 4 / Hall / FlexG1 · 24 · AN temp 3 / Hall / FlexH4 · 17 · Sensor groundG4 · 21 · Sensor ground

TPS and pedal

Cable throttle: H1 is TPS, 5 V from B1, ground on H4 / G4. Closed ~0.4–0.8 V, WOT 3.8–4.7 V, monotonic. Drive-by-wire adds throttle TPS 2 on F3 and pedal PPS 1 / PPS 2 on E2 and E3.

Pins: H1 · 20 · TPS 1F3 · 26 · AN volt 2E2 · 31 · AN volt 3E3 · 30 · AN volt 7B1 · 44 · TPS 5 V

MAP and 0–5 V

F2 is the default MAP input. 5 V from C2. Remaining analog pins — H2, F1, E1, D1, C1 — take oil pressure, fuel pressure, wideband analog, or whatever the tune assigns. All aux-reuse pins on V4 are analog inputs.

Pins: F2 · 27 · AN volt 1C2 · 39 · MAP 5 VH2 · 19 · AN volt 4F1 · 28 · AN volt 10E1 · 32 · AN volt 6D1 · 36 · AN volt 8C1 · 40 · AN volt 9

03 Crank, cam, flex & VSS

One VR crank pair, one dedicated Hall input, two multi-use Hall / flex / temp pins. No RPM on A4 means the engine will not fuel or spark.

VR crank

Most OEM crank sensors on 36-1, 60-2 and 12-1 wheels are VR. VR+ to A4, VR− to A3, twisted pair, shield earthed at the ECU analog ground only. If you see RPM while cranking but the engine will not sync, swap A4 and A3 before touching the trigger-type setting.

Pins: A4 · 45 · Crank VR+ / HallA3 · 46 · Crank VR−

Hall crank

Three-wire Hall: 5 V or 12 V supply, signal to A4, ground to sensor ground. Leave A3 unconnected.

Cam, VSS, flex

F4 is the primary Hall input (cam by default). G3 and G1 can be Hall, flex-fuel frequency, VSS, or thermistors. Sequential 4-cylinder COP needs a cam. 6- and 8-cylinder batch / wasted spark run on crank only — F4 is then free for wheel speed.

Pins: F4 · 25 · Hall camG3 · 22 · AN temp 4 / Hall / FlexG1 · 24 · AN temp 3 / Hall / Flex

04 Injectors · 4 / 6 / 8 cyl

Four primary high-Z injector drivers. Cylinder count is assignable: 4-cyl sequential on those four, 6-cyl 3-channel matched through an external driver on K1 / J3 / J4, 8-cyl two-channel batch through J4 / J3.

The four primary outputs

C4, C3, B4, B3 are Injector 1–4. The ECU switches ground. Injector 12 V comes from main-relay 87. Cylinder order is a TunerStudio table.

Pins: C4 · 37 · Injector 1C3 · 38 · Injector 2B4 · 41 · Injector 3B3 · 42 · Injector 4

4-cylinder — sequential

One injector per primary output. Sequential with a cam on F4, or batch/semi-sequential on crank only.

6-cylinder — 3-channel matched

Three matched batch channels through an external injector driver. Trigger that box from K1 (Ignition 4), J3 (GPO 5) and J4 (GPO 6). Two injectors per channel. Primary Inj 1–4 stay unused for fuel. Confirm 5 V vs 12 V jumper on GPO 5 / 6, and that Ign 4 is set as a fuel output — not a coil — in TunerStudio.

Pins: K1 · 12 · Ignition 4J3 · 14 · GP Out 5J4 · 13 · GP Out 6

8-cylinder — two-channel batch

Two injector channels: J4 (GP Out 6, Injectors A) and J3 (GP Out 5, Injectors B) into an external driver. Four injectors per channel. Primary Inj 1–4 stay unused for fuel. Confirm 5 V vs 12 V jumper on GPO 5 / 6.

Pins: J4 · 13 · GP Out 6J3 · 14 · GP Out 5

05 Ignition · 4 / 6 / 8 cyl

Four 5 V logic-level coil triggers plus two GP highs. Cylinder count is assignable. Dumb coils need an igniter — these pins will not drive them.

Pins: K4 · 9 · Ignition 1K3 · 10 · Ignition 2K2 · 11 · Ignition 3K1 · 12 · Ignition 4J3 · 14 · GP Out 5J4 · 13 · GP Out 6

4-cylinder

Smart coils on K4–K1 (Ignition 1–4). Wasted spark with two coils, or sequential COP with four coils plus a cam on F4. Coil +12 V from main-relay 87. Coil power ground to the head, not analog ground.

6-cylinder — wasted spark

Three logic coils on K4, K3, K2 (Ignition 1–3). Two cylinders per coil. Ignition 4 (K1) is taken by the 6-cyl 3-channel injector driver — do not also put a coil on it.

8-cylinder — wasted spark

Four logic outputs on K4–K1, wasted spark (two cylinders per coil). Pair cylinders 360° apart. Example 1UZ-FE order 1-8-4-3-6-5-7-2 pairs as 1&6, 8&5, 4&7, 3&2 — assign whatever firing order the engine actually has. GPO 5 / 6 are then free for the two-channel injector driver.

Lock timing to a fixed 10° and confirm with a light on cylinder 1 before you add load. If the light is 180° out, add 360° to the offset or swap wasted-spark pairs — do not guess with fuel in the hole.

06 Drive-by-wire

One H-bridge on M1 and L1, throttle TPS 1/2, pedal PPS 1/2. Cable-throttle cars leave the H-bridge empty.

Pins: M1 · 4 · ETB+L1 · 8 · ETB−H1 · 20 · TPS 1F3 · 26 · AN volt 2E2 · 31 · AN volt 3E3 · 30 · AN volt 7

Motor

ETB+ M1, ETB− L1. If the blade drives closed on a positive test, swap the two wires or invert the output in firmware.

Sensors

Throttle-body TPS 1 on H1, TPS 2 on F3. Pedal PPS 1 on E2, PPS 2 on E3. Each needs 5 V (B1) and sensor ground. Two independent wipers, not a Y-splice of one signal.

07 VVT, pump, fan & spare

Two dedicated high-current low-sides plus four half-bridges. Roles are assignable — fuel pump, fan, boost, VVT, stepper.

Dedicated low-sides

L2 is Low-side 1, M2 is Low-side 2. Typical: VVT and idle, or dual VVT. Solenoid 12 V from the main relay.

Pins: L2 · 7 · Low-side 1M2 · 3 · Low-side 2D2 · 35 · GP Out 1D3 · 34 · GP Out 2D4 · 33 · GP Out 3B2 · 43 · GP Out 4

Fuel pump and fan

Typical assignment is GP Out 1 (D2) for the fuel-pump relay and GP Out 2 (D3) for the fan relay. Relay coils only. Pump power on its own 15–20 A fused feed. Firmware primes on key-on.

GPO 5 and GPO 6

J3 and J4 are push-pull logic. On a 4-cylinder they are free for tach, shift light or an extra coil. On a 6-cylinder they share the 3-channel matched injector driver with K1. On an 8-cylinder they trigger the two-channel injector driver. Do not double-assign them.

Stepper idle

Bipolar stepper idle valves can use the four half-bridges (D4, D3, D2, B2) as two coils. Unipolar (5-wire / 6-wire) steppers are not supported. DBW cars should not also run a stepper.

08 CAN & Core EFI dash

A1 / A2 are the CAN pair. The Core EFI 7-inch dash speaks the Core EFI protocol on this bus. 120 Ω at each end.

Pins: A1 · 48 · CAN HighA2 · 47 · CAN Low

Physical layer

Twisted pair, CAN H A1, CAN L A2. 1 Mbit/s is the Core EFI default. A 120 Ω terminator belongs at each end of the bus — inside the dash and inside the ECU, or as a plug-in resistor on the last device.

Core EFI 7-inch dash

The Race Shop 7-inch dash listed as ‘Core EFI Protocol’ is the matching unit (the non-Core protocol dash is for Haltech / ECUMaster / Link / AEM). Power the dash from a fused ignition feed, ground it to chassis, CAN H/L to A1 / A2. Enable the dash broadcast in TunerStudio.

USB for tuning

TunerStudio talks USB, not CAN. J2 (D−, white) and J1 (D+, green), or the internal micro-USB. Shielded cable, one ground between laptop and ECU — the USB ground.

Pins: J2 · 15 · USB D−J1 · 16 · USB D+

09 Firmware & TunerStudio

Core EFI loader for firmware, TunerStudio for the tune. Loaders and ini files live on the Race Shop support drive. Cylinder count, injection mode and pin functions are assignable in the project.

What runs on the box

V4 runs Core EFI firmware, tuned in TunerStudio. Use the Core EFI V4 loader from the Race Shop support page — not a binary from another Core EFI product.

Update via Auto DFU

1. 01
   Talk USB first

   Windows Device Manager should show ‘STMicroelectronics Virtual COM Port’. If it does not, install the ST VCP driver before you try DFU.

2. 02
   Auto DFU from the console

   Open the Core EFI console, pick the COM port, Update Firmware. The activity LED stops, the VCP disappears, ‘STM Device in DFU Mode’ appears, then erase + download.

3. 03
   Power cycle

   When the console reports Upgrade successful / Verify successful, key-off, wait 10 seconds, key-on. Confirm the new version string.

TunerStudio project

• New project → load the Core EFI V4 ini that shipped with that firmware.
• Set cylinder count, injection mode (sequential / batch) and ignition mode (COP / wasted spark) to match the engine. 6-cyl fuel is 3-channel matched on Ign 4 / GPO 5 / GPO 6 — assign those as injector-driver outputs, not coils.
• Assign spare analog and GP pins to the sensors and relays actually fitted.
• Calibrate TPS, CLT, IAT, MAP, AFR before you crank.
• Save the .msq off the laptop.

10 First start

Garage checklist. Fuel last. Work the list in order.

11 Faults

Most first-start failures are power, crank signal, or a driver fighting a short. Work the list in order — do not retune a dead trigger.

Dead ECU / no USB

• L4 has key-on 12 V to ECU ground.
• M3 and L3 are on a real engine earth.
• E4 is grounding the relay coil; M4 then shows 12 V.
• USB: J2 white, J1 green, shielded cable, ST VCP driver installed.

No RPM while cranking

• VR: A4 / A3, twisted, swap polarity once.
• Hall: A4 only, A3 open, sensor actually powered.
• Trigger type and tooth count match the wheel.
• Look at the composite logger in the Core EFI console before you touch fueling.

RPM yes, no fuel

• 4-cyl: C4, C3, B4, B3 actually clicking on the output test.
• 6-cyl: K1, J3, J4 toggling into the 3-channel injector driver, and that box has 12 V.
• 8-cyl: J4 / J3 toggling into the external driver, and that box has 12 V.
• Injector +12 V from main-relay 87.
• Fuel-pump relay on D2 clicks.

No spark

• 4-cyl / 8-cyl wasted spark: smart coil or igniter on K4–K1.
• 6-cyl: smart coils on K4, K3, K2. K1 is the injector driver, not a coil.
• Coil +12 V present while cranking (relay 87).
• Fixed-timing test at 10° with a light on cylinder 1.

Sync loss under load

• Shield the crank pair. Cross it away from injector and coil looms.
• Power ground on the block, not a painted chassis hole.
• VR gap too large, or a cracked reluctor.