1993 - 1995 Mazda RX-7 ECU

ECU - Electronic Control Unit Connector.

The 1993–1995 Mazda RX-7 FD3S is equipped with a proprietary Mazda EGI (Electronic Gasoline Injection) ECU that manages the 13B-REW twin-rotor twin-sequential-turbocharged rotary engine. The ECU is located behind the passenger-side kick panel in the footwell and interfaces with the engine harness via four wiring connectors. Beyond standard EFI functions such as fuel injection, ignition timing, and sensor monitoring, the ECU governs the sequential twin-turbocharger switching logic controlling both primary and secondary turbo actuators. Key signals include the NE crank-position input, G cam-position input, throttle position, MAP sensor, pre- and post-catalyst oxygen sensors, and four fuel injectors with leading and trailing ignition coil outputs.

Connector 1

Connector 2

Connector 3

Connector 4

Notes

The ECU uses two primary wiring connectors designated X-05 (blue plug, engine harness) and X-14 (dash/body harness) in factory wiring documentation. US-market FD3S pinouts differ from JDM specification. Engine Control, Fuel Control, and Ignition systems are co-indexed at section Z-28 in the 1993 factory wiring supplement; the Diagnosis Connector is at Z-112. The 1993 US-market ECU carries Mazda part number N3A7-18-881A. Wire colours follow Mazda convention: B=Black, W=White, R=Red, G=Green, Y=Yellow, L=Blue, O=Orange, Lg=Light green.

Signals

• Vehicle Speed Sensor — vehicle speed signal input to ECU (connector 1, pin 1M)
• MAP Sensor — manifold absolute pressure analogue input for load calculation (connector 1, pin 1O)
• Brake Switch — brake pedal state input (connector 1, pin 1S)
• Tachometer output — engine RPM output signal to instrument cluster (connector 2, pin 2B)
• Primary O2 Sensor — pre-catalyst oxygen sensor analogue input for closed-loop fuelling (connector 3, pin 3C)
• Engine Coolant Temperature Sensor — coolant temperature analogue input for fuelling and fan control (connector 3, pin 3E)
• Throttle Position Sensor — throttle angle analogue input for load and acceleration enrichment (connector 3, pin 3F)
• Intake Air Temperature Sensor — intake air temperature analogue input for charge-density correction (connector 3, pin 3L)
• Power Ground — ECU power ground return (connector 4, pin 4A)

References

• 1993 Mazda RX-7 Wiring Diagrams (Factory Service Manual supplement)
• 1994 Mazda RX-7 Wiring Diagram (Factory Service Manual supplement)
• ‘94 Mazda RX-7 Factory Service Manual (Internet Archive)

Category:Car Connectors