MBE ECU pinout and wiring reference
This page documents the wiring of the MBE 9A4/967-style engine management ECU as fitted to TVR models running the Speed Six straight-six and AJP V8 (Cerbera, Tuscan, Tamora, T350, Sagaris). It is a transcription of an ECU wiring diagram showing sensor inputs on one side, injector and coil drivers on the other, and a 19-way male multiplug forming the chassis-side interface.
Use this as a reference when tracing faults, repinning a connector, or sanity-checking an aftermarket loom. The MBE ECU uses a single large multiway connector at the unit itself; the pin numbers below refer to that ECU header. Always confirm against your own car — looms vary between models and years, and previous owners may have rewired things.
ECU pin map
Section titled “ECU pin map”The central ECU connector terminations as labelled on the diagram:
| Pin | Function |
|---|---|
| 2 | MAP sensor signal |
| 3 | Lambda 2 (even bank) |
| 6 | Radiator fan 2 |
| 7 | Ground (0 V) |
| 13 | Crank position sensor + |
| 14 | Diagnostics / ECU fault to dash |
| 17 | Air charge temperature (ACT) |
| 18 | TPS2 (even bank) signal |
| 19 | Coil drive A |
| 20 | Coil ground |
| 21 | Lambda 1 (odd bank) |
| 23 | Air-con request input |
| 25 | Fuel pump drive |
| 26 | Ground (0 V) |
| 27 | Crank position sensor − |
| 33 | Tacho output |
| 35 | TPS1 (odd bank) signal |
| 36 | Engine coolant temperature (ECT) |
| 38 | Injector bank 1 (odd) drive |
| 40 | Coil ground |
| 41 | Radiator fan 1 |
| 42 | Air-con acknowledge |
| 44 | Shift lamp |
| 48 | 5 V Vref out |
| 49 | Signal return (Sigrtn) |
| 50 | Ground (0 V) |
| 51 | Ground (0 V) |
| 52 | 12 V ECU power |
| 53 | Injector bank 2 (even) drive |
| 55 | Coil drive B |
Pin 14 appears twice on the source diagram, labelled both “Diag” and “ECU fault to dash” — in practice the same line is used for both functions.
Sensor inputs
Section titled “Sensor inputs”All temperature and position sensors share the ECU’s Sigrtn (pin 49) as their analogue ground; do not bond their grounds to chassis or you will pick up offsets. The 5 V Vref (pin 48) feeds the potentiometric sensors (throttle bodies, MAP).
| Sensor | Connector | Pin | Goes to |
|---|---|---|---|
| ACT (air charge temp) | 2-pin | 1 | ECU 17 |
| ACT | 2 | Sigrtn (ECU 49) | |
| ECT (coolant temp) | 2-pin | 1 | ECU 36 |
| ECT | 2 | Sigrtn | |
| TPS1 (odd bank) | 3-pin | 1 | 5 V Vref |
| TPS1 | 2 | ECU 35 | |
| TPS1 | 3 | Sigrtn | |
| TPS2 (even bank) | 3-pin | 1 | 5 V Vref |
| TPS2 | 2 | ECU 18 | |
| TPS2 | 3 | ECU 48 (5 V Vref) | |
| Lambda 1 (odd) | 3-pin | 1 | 12 V (fused) – heater |
| Lambda 1 | 2 | 0 V | |
| Lambda 1 | 3 | ECU 21 | |
| Lambda 2 (even) | 3-pin | 1 | 12 V (fused) – heater |
| Lambda 2 | 2 | 0 V | |
| Lambda 2 | 3 | ECU 3 | |
| Crank position | 2-pin shielded | 1 | ECU 27 (CPS −) |
| Crank position | 2 | ECU 13 (CPS +) | |
| Crank position | shield | – | Sigrtn |
| MAP | 3-pin | A | 0 V |
| MAP | B | ECU 2 | |
| MAP | C | 5 V Vref |
The crank sensor screen must only be terminated at one end (Sigrtn at the ECU) to avoid a ground loop that introduces noise into the trigger signal.
Injector and ignition outputs
Section titled “Injector and ignition outputs”The ECU drives injectors and coils on the low side — the 12 V feed sits permanently on one pin of each device, and the ECU pulls the other pin to ground to fire it. Injectors are wired in two banks; the source diagram daisy-chains the drive side of all four odd-bank injectors back to ECU pin 38, and all four even-bank injectors back to ECU pin 53.
| Output | Connector | Pin | Goes to |
|---|---|---|---|
| Injectors 1, 3, 5, 7 (odd) | 2-pin each | 1 | ECU 38 (Inj bank 1, daisy-chained) |
| Injectors 1, 3, 5, 7 | 2 | 12 V (fused) | |
| Injectors 2, 4, 6, 8 (even) | 2-pin each | 1 | ECU 53 (Inj bank 2, daisy-chained) |
| Injectors 2, 4, 6, 8 | 2 | 12 V (fused) | |
| Coil pack (even) | 4-pin | 1 | ECU 19 (coil drive A) |
| Coil pack (even) | 2 | ECU 20 (coil ground) | |
| Coil pack (even) | 3, 4 | 12 V (fused) | |
| Coil pack (odd) | 4-pin | 1 | ECU 40 (coil ground) |
| Coil pack (odd) | 2 | ECU 55 (coil drive B) | |
| Coil pack (odd) | 3, 4 | 12 V (fused) | |
| Diagnostic socket | 2-pin | 1 | ECU 14 (Diag) |
| Diagnostic socket | 2 | 0 V |
19-way chassis multiplug
Section titled “19-way chassis multiplug”This is the male multiplug on the engine-bay side of the loom that carries the bulk of the ECU’s interface with the rest of the car: switched power, fan and pump drives, lambda heater feeds, and dash signals. Pins marked “Big Pin” carry higher current and use the larger terminal size in the housing.
| Pin | Function |
|---|---|
| 1 | ECU 25 – fuel pump drive |
| 2 | ECU 6 – radiator fan 2 |
| 3 | 12 V to lambda heaters (fused) |
| 4 | Oil pressure switch |
| 5 | 12 V to alternator from warning lamp |
| 6 | 12 V permanent (not connected to ECU) |
| 7 | 12 V to injectors (fused, big pin) |
| 8 | 12 V feed to starter solenoid (big pin) |
| 9 | 12 V to coil – odd bank (fused, big pin) |
| 10 | 12 V to coil – even bank (fused, big pin) |
| 11 | ECU 44 – shift lamp |
| 12 | ECU 14 – diagnostics / fault to dash |
Pins 13–19 of the multiplug were not legible in the source — verify the remainder against the original diagram or a known-good loom before relying on them.
Notes and cautions
Section titled “Notes and cautions”- Engine management wiring is safety-critical. A miswired injector or coil feed can damage the ECU, set fire to a loom, or leave the car undriveable. Double-check every pin with a meter before applying power.
- The two coil packs use opposite polarity at the connector — odd bank has ground on pin 1 and drive on pin 2, even bank has drive on pin 1 and ground on pin 2. It is easy to swap them by mistake.
- Lambda heaters draw significant current; make sure their 12 V feed is properly fused and that the heater ground is solid, otherwise you will see slow or failed sensor warm-up.
- If you are converting to an Emerald, Syvecs or other aftermarket ECU, you cannot assume the pin numbering carries over — only the sensor and actuator wiring on the engine side stays the same.
Compiled from a community-uploaded MBE ECU wiring diagram for TVR Speed Six and AJP V8 applications — always verify against the original document and your own loom before relying on it.