OBD2 B Series VTEC Distributor Wiring Guide for Honda Engine Swaps

Swapping engines in 1992-2000 Honda Civics is a popular modification for car enthusiasts looking to boost performance. A frequently asked question revolves around engine wiring, especially when incorporating VTEC systems and different OBD (On-Board Diagnostics) standards. This comprehensive guide addresses the common wiring scenarios for engine swaps in 92-00 Civics, with a particular focus on Obd2 B Series Vtec Distributors and their integration into various setups. Whether you’re dealing with a B series VTEC engine or navigating different OBD generations, this guide aims to clarify the wiring process, ensuring a smoother engine swap experience.

Understanding OBD and Distributor Compatibility for Honda Swaps

When performing an engine swap in a 92-00 Honda Civic, understanding OBD generations (OBD0, OBD1, OBD2) is crucial for proper wiring and ECU (Engine Control Unit) compatibility. The distributor, a key component in engine ignition, is also affected by these OBD standards. This guide breaks down the wiring considerations when using an OBD2 B series VTEC distributor in your Honda Civic swap project.

OBD1 Engine/ECU into OBD1 Civic (1992-1995)

For 92-95 Civics, which are natively OBD1, swapping in an OBD1 engine and ECU is generally the most straightforward process. The VTEC wiring is often pre-run in these models, simplifying the integration of VTEC engines.

(Note: For all 1992 Civics, the VTEC wiring is pre-wired to the ECU harness on the shock tower. Utilizing a 92-95 EX/SI engine harness makes VTEC plug-and-play. See Figure 5)**

D16Z6/D15B (JDM)/Mini-Me Swaps with P28 ECU

• DX/LX (D15B7): Wiring the VTEC solenoid and VTEC pressure switch to the P28 ECU is necessary. All other connections are typically plug-and-play. (See Figure 1)
• CX (D15B8): Similar to DX/LX, VTEC solenoid and pressure switch wiring to the P28 ECU is required (Figure 1). For CX models that are not 4-wire O2 sensor configurations, wiring the additional three O2 sensor connections to the ECU is needed (Figure 1).
• VX (D15Z1): VTEC wiring follows the same procedure as above. For knock sensor and IAB (Intake Air Bypass) wiring, refer to Figure 1. If using a chipped P28 ECU, IAB and knock sensor wiring may not be necessary. VX models with 7-wire O2 sensors will need conversion to 4-wire (diagram available at http://www.hybridautomotive.com/tech/o2/).

B16A3/B17A/B18C1/B18C (OBD1 JDM) with Chipped P28/P30/P61/P72 ECU

• EX/Si (D16Z6): VTEC is typically plug-and-play. Knock sensor and IAB wiring are shown in Figure 1, but may be bypassed with a chipped P28 ECU.
• DX/LX (D15B7): VTEC wiring is required (Figure 1). Knock sensor and IAB wiring are also in Figure 1, and can be skipped with a P28 ECU.
• CX (D15B8): VTEC, knock sensor, and IAB wiring are needed as per Figure 1, with potential bypass for knock and IAB using a chipped P28. Non-4-wire CX models require additional O2 sensor wiring (Figure 1).
• VX (D15Z1): VTEC solenoid and pressure switch wiring can be reused. 7-wire O2 sensor conversion might be necessary.

B18A (OBD1)/B18B in DX/CX/VX/EX using P74/P75 ECU or Chipped OBD1 ECUs

• LX/DX/EX (D15B7/D16Z6): Plug-and-play.
• CX/VX (D15B8/D15Z1): Plug-and-play. 1-wire O2 CX models require 4-wire O2 sensor wiring (Figure 1). 7-wire VX O2 sensors might need conversion.

OBD2 Engine/OBD1 ECU into OBD1 Vehicle (1992-1995)

Integrating an OBD2 engine into an OBD1 Civic requires more attention to wiring, especially when using an OBD1 ECU. OBD2 B series VTEC distributors will need adapters for OBD1 compatibility in these scenarios.

(Note: For 92 Civics, VTEC wiring is pre-run. EX/SI 92-95 engine harnesses simplify VTEC connections.)

D16Y8 with P28 ECU

• EX/Si/VX (D16Z6/D15Z1): Mostly plug-and-play for basic functions. VTEC is plug-and-play. The knock sensor is not utilized by the P28 ECU. The EX/Si/VX distributor may not directly bolt onto the Y8 head; using it might require only some legs to be bolted. To use the Y8 distributor, an OBD2A or OBD2B to OBD1 adapter harness is necessary. The intake air temperature sensor location differs on the Y8, requiring relocation to the intake arm (Figure 3) or using a Z6/Z1 manifold. Reuse Z6 injectors as Y8 injectors are incompatible. For VX models, consider EX/SI/DX injectors for similar flow rates. Reuse the Z6/Z1 alternator due to plug differences. The CKF sensor on the Y8 crank is not used and should be secured away. VX models may need 5-wire to 4-wire O2 sensor conversion (http://www.hybridautomotive.com/tech/o2/).
• LX/DX/CX (D15B7/D15B8): Mostly plug-and-play. VTEC solenoid and pressure switch wiring is needed (Figure 1). Reuse the DX/CX distributor as it should bolt on. To use a Y8 distributor, an OBD2A or OBD2B to OBD1 adapter harness is needed. IAT sensor relocation or CX/DX manifold usage is necessary as with the EX/Si/VX. DX injectors can be reused due to similar flow rates. CX models should upgrade to EX/SI/DX injectors for better flow matching the Y8. Reuse the CX/DX alternator. CKF sensor is not used and should be tied off.

B16A2/B18C1 (OBD2)/B18C5 with Chipped P28/P30/P72 ECU

• EX/SI/VX (D16Z6/D15Z1): Mostly plug-and-play. VTEC is plug-and-play. Knock sensor is not used with P28 but is with other ECUs. To use an A2/C1/C5 distributor, an OBD2A or OBD2B to OBD1 adapter harness is required. IAT sensor relocation is necessary (see pic). Reuse Z6 injectors as A2/C1/C2 injectors are incompatible. VX models will need EX/SI/DX injectors for similar flow. An OBD1 B series alternator is needed for plug-and-play. CKF sensor is unused. VX models may need 5-wire to 4-wire O2 conversion (http://www.hybridautomotive.com/tech/o2/).
• DX/CX (D15B7/D15B8): Mostly plug-and-play. VTEC wiring is needed (Figure 1). Knock sensor not used with P28 but is with others. OBD2 B series VTEC distributor requires an OBD2A or OBD2B to OBD1 adapter harness. IAT sensor relocation is needed. Reuse DX injectors; CX models require EX/SI/DX injectors. OBD1 B series alternator needed. CKF sensor is not used. 1-wire O2 CX models need 4-wire conversion (Figure 1).

B18B/B20B/Z (OBD2) with P75 ECU

• EX/SI/VX/DX/CX (D16Z6/D15Z1/D15B7/D15B8): Mostly plug-and-play. For the distributor, use an OBD1 B18 distributor for plug-and-play or an OBD2 LS distributor with an adapter harness. An OBD1 B series alternator is required. EX/SI/DX injectors can be reused; VX/CX models need EX/DX/SI injectors. CKF sensor is not used. 1-wire O2 CX models need 4-wire conversion (Figure 1). VX 7-wire O2 may need 4-wire conversion (http://www.hybridautomotive.com/tech/o2/).

OBD0 Engine into OBD1 Vehicle using OBD1 ECU

Swapping an OBD0 engine into an OBD1 Civic is less common but achievable.

B18A (OBD0) with P75 OBD1 ECU

• EX/SI/DX/CX/VX (D16Z6/D15Z1/D15B7/D15B8): Mostly plug-and-play. OBD0 and OBD1 alternators use the same plugs. Reuse EX/SI/DX injectors; CX/VX need EX/SI/DX injectors. The fan switch location is different on OBD0 engines (back of the block). Rewire the fan switch from the thermostat housing to the back of the block. Wiring order doesn’t matter. VX 7-wire O2 and CX 1-wire O2 models need 4-wire conversion (Figure 1, http://www.hybridautomotive.com/tech/o2/).

OBD2 Engine into OBD2 Vehicle using OBD2 ECU (1996-2000)

(NOTE: 96-98 OBD2A and 99-00 OBD2B ENGINE and DASH HARNESSES are NOT interchangeable due to different ECU connectors. See Figure 11)

D16Y8 with P2P ECU

• DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid, VTEC pressure switch, and knock sensor wiring is needed (Figure 6 for OBD2A, Figure 7 for OBD2B). IACV (Idle Air Control Valve) wiring from 3-wire to 2-wire is also required (Figure 6, Figure 7). The secondary O2 sensor wiring might need extension with an O2 adapter if using an EX catalytic converter. IAT sensor relocation is necessary (Figure 8).
• HX (D16Y5): Mostly plug-and-play. Reuse VTEC solenoid and pressure switch. 5-speed models need knock sensor wiring (Figure 6, all HX models 96-00 are OBD2A wired). 7-wire O2 needs 4-wire conversion (eastcoasthondas.com – eastcoasthondas Resources and Information.).

B16A2/B18C1/B18C5 with P30 (OBD2A)/P2T/P72 ECU

• EX (D16Y8): Mostly plug-and-play. Reuse VTEC, pressure switch, and knock sensor wiring. Secondary O2 may need extension. For B18C1, IAB wiring to P72 ECU is necessary (Figure 6, Figure 7). IAT sensor relocation is needed (Figure 8). For B18C1/C5, convert to round style IAT (Figure 9).
• DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC, pressure switch, and knock sensor wiring needed (Figure 6, Figure 7). IACV wiring (3-wire to 2-wire) is also needed (Figure 6, Figure 7). Secondary O2 extension might be required. IAT sensor relocation is necessary (Figure 8). For B18C1/C5, round style IAT conversion is possible (Figure 9).
• HX (D16Y5): Mostly plug-and-play. Reuse VTEC and pressure switch. 5-speed models need knock sensor wiring (Figure 6). 7-wire O2 to 4-wire conversion is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.).

B18B/B20B/Z using OBD2A P75 ECU (00-01 P75 with immobilizer is not recommended)

• EX/HX (D16Y8/D16Y5): Plug-and-play. HX 7-wire O2 needs 4-wire conversion (eastcoasthondas.com – eastcoasthondas Resources and Information.).
• DX/LX/CX (D16Y7): Mostly plug-and-play. IACV wiring (3-wire to 2-wire) is needed (Figure 6, Figure 7). Secondary O2 extension might be required. IAT sensor relocation is necessary (Figure 8).

OBD1 Engine into OBD2 Vehicle using OBD1 ECU

Using an OBD1 ECU in an OBD2 Civic requires additional adaptations.

D16Z6 using P28 ECU

• DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid and pressure switch wiring is needed (Figure 1). IACV wiring (3-wire to 2-wire) is also needed (Figure 6, Figure 7). IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is required. CKF, EVAP purge, and secondary O2 are eliminated. A D16Z6 distributor will need an adapter. Use Z6 injectors (remove injector “clips” for plug-and-play, Figure 10). Reuse the Y7 alternator or use an adapter.
• HX (D16Y5): VTEC is plug-and-play. IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is needed. CKF, EVAP purge, EGR, and secondary O2 are eliminated. 7-wire O2 to 4-wire conversion is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.). D16Z6 distributor needs adapter. Use Z6 injectors (remove clips, Figure 10). Reuse Y7 alternator or adapter.
• EX (D16Y8): VTEC is plug-and-play. IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is needed. CKF, EVAP purge, EGR, and secondary O2 are eliminated. D16Z6 distributor needs adapter. Use Z6 injectors (remove clips, Figure 10). Reuse Y7 alternator or adapter.

B16A2/B18C1/B18C5 using OBD1 P30 ECU

• DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid, pressure switch, and knock sensor wiring is needed (Figure 1). IACV wiring (3-wire to 2-wire) is also needed (Figure 6, Figure 7). IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is required. CKF, EVAP purge, and secondary O2 are eliminated. For 96-98 Civics, use an OBD2 B series VTEC distributor for plug-and-play or an OBD2A to OBD1 distributor adapter. For 99-00, use an OBD2B to OBD1/2 distributor adapter and OBD1/2 B series DOHC VTEC distributor. Use B series injectors (remove clips, Figure 10). Use an OBD2 B series alternator or an OBD2-1 alternator adapter.
• HX (D16Y5): VTEC is plug-and-play. IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is needed. CKF, EVAP purge, EGR, and secondary O2 are eliminated. 7-wire O2 to 4-wire conversion is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.). Use an OBD2 VTEC distributor or an OBD2A to OBD1 distributor adapter. Use B series injectors (remove clips, Figure 10). Use an OBD2 B series alternator or OBD2-1 adapter.
• EX (D16Y8): VTEC is plug-and-play. Knock sensor wiring is needed (Figure 1). IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is required. CKF, EVAP purge, EGR, and secondary O2 are eliminated. For 96-98 Civics, use an OBD2 B series VTEC distributor or OBD2A to OBD1 distributor adapter. For 99-00, use OBD2B to OBD1/2 distributor adapter and OBD1/2 B series DOHC VTEC distributor. Use B series injectors (remove clips, Figure 10) or Y8 injectors. Use OBD2 B series alternator or OBD2-1 adapter.

B18A/B using OBD1 P75 ECU

• DX/LX/CX (D16Y7): Mostly plug-and-play. IACV wiring (3-wire to 2-wire) is needed (Figure 6, Figure 7). Secondary O2 extension might be needed. IAT sensor relocation (Figure 8) is necessary. CKF, EVAP purge, EGR, and secondary O2 are eliminated. Use an OBD2 B18B distributor or OBD2A to OBD1 distributor adapter. For 99-00 Civic, use OBD2B to OBD1 distributor adapter with either an OBD1 or OBD2 B18A/B distributor. Use B18A/B injectors (remove clips, Figure 10). Use OBD2 B series alternator or OBD2-1 adapter.
• EX/HX (D16Y8/Y5): IAT sensor relocation (Figure 8) or OBD1 style IAT wiring (Figure 9) is needed. CKF, EVAP purge, EGR, and secondary O2 are eliminated. For 96-98 Civics, use an OBD2 B18B distributor or OBD2A to OBD1 distributor adapter. For 99-00, use OBD2B to OBD1/2 distributor adapter and OBD1/2 B series DOHC VTEC distributor. Use B18A/B injectors (remove clips, Figure 10). Use OBD2 B series alternator or OBD2-1 adapter. HX 7-wire O2 needs 4-wire conversion (eastcoasthondas.com – eastcoasthondas Resources and Information.).

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Figure 1: OBD1 ECU Wiring

Figure 2: JDM VTEC Solenoid

JDM VTEC Solenoid

Figure 3: OBD1 IAT Sensor in Intake Arm

Figure 4: OBD0 Fan Switch vs OBD1 Fan Switch

Figure 5: OBD1 Shock Tower Harness

Figure 6: OBD2A Hybrid Pinouts (96-98)

Figure 7: OBD2B Hybrid Pinouts (99-01)

Figure 8: OBD2 IAT Sensor in Intake Arm

Figure 9: Round Style IAT Sensor

Figure 10: OBD2 to OBD1 Injector Clip Modification

Figure 11: OBD2A vs OBD2B Harness Comparison