Swapping engines in your 1992-2000 Honda Civic, including the popular Del Sol, can significantly boost performance and breathe new life into your ride. However, navigating the intricacies of wiring, especially when dealing with different OBD (On-Board Diagnostics) systems, can seem daunting. This guide simplifies the process, providing a comprehensive overview of wiring considerations for various engine swaps in 92-00 Civics, ensuring a smoother and more successful project. Whether you’re upgrading to a VTEC engine or dealing with OBD1 to OBD2 conversions, understanding these wiring nuances is crucial.
OBD1 Engine/ECU into OBD1 Civic (1992-1995)
For 1992-1995 Civics, which are inherently OBD1, swapping in an OBD1 engine and ECU is generally the most straightforward path.
(Note: For all 1992 Civics, the VTEC wiring is pre-run on the shock tower to ECU harness. Utilizing a 1992-1995 EX/Si engine harness makes VTEC installation plug-and-play.)
D16Z6/D15B (JDM)/Mini-Me with P28 ECU
If you’re opting for a D16Z6, JDM D15B, or a Mini-Me swap using a P28 ECU, the process is largely plug-and-play.
(Note: If your JDM D15B engine lacks a VTEC pressure switch, you’ll need to install one from any 1990-2001 Civic, Integra, or Accord. See Figure 2 for visual guidance.)
- DX/LX (D15B7): Wiring the VTEC solenoid and VTEC pressure switch to the P28 ECU is necessary. All other connections should be plug-and-play. (Refer to Figure 1 for wiring details.)
- CX (D15B8): Similar to DX/LX, VTEC solenoid and pressure switch wiring to the P28 ECU is required (Figure 1). If your CX model uses a 1-wire O2 sensor system (non-4 wire), you’ll need to wire the additional three O2 sensor connections to the ECU as shown in Figure 1.
- VX (D15Z1): VTEC wiring follows the same procedure as above. For knock sensor and IAB (Intake Air Bypass) wiring, consult Figure 1. (Note: If using a chipped P28 ECU, IAB and knock sensor wiring might not be necessary.) If your VX model has a 7-wire O2 sensor, conversion to a 4-wire setup is required. Diagrams for 7-wire to 4-wire conversion are available online.
B16A3/B17A/B18C1/B18C (OBD1 JDM) with Chipped P28/P30/P61/P72 ECU
For B-series engine swaps like B16A3, B17A, B18C1, or OBD1 JDM B18C, using a chipped OBD1 ECU (P28, P30, P61, P72) simplifies the wiring process.
- EX/Si (D16Z6): VTEC wiring is plug-and-play. Knock sensor and IAB wiring are shown in Figure 1. (Note: Chipped P28 ECUs might eliminate the need for IAB and knock sensor wiring.) All other wiring is typically plug-and-play.
- DX/LX (D15B7): VTEC, knock sensor, and IAB wiring are needed as per Figure 1. (Note: P28 ECU might negate IAB and knock sensor wiring.) The rest of the wiring should be plug-and-play.
- CX (D15B8): VTEC, knock sensor, and IAB wiring are needed (Figure 1). (Note: Chipped P28 negates IAB/knock sensor wiring.) If your CX is not a 4-wire O2 sensor model, wire the additional O2 connections (Figure 1). Other wiring aspects are generally plug-and-play.
- VX (D15Z1): Reuse existing VTEC solenoid and pressure switch wiring for plug-and-play VTEC. For 7-wire O2 sensor VX models, convert to 4-wire using online diagrams.
B18A (OBD1)/B18B in DX/CX/VX/EX using P74/P75 ECU or Chipped OBD1 ECUs
When installing OBD1 B18A or B18B engines into DX, CX, VX, or EX Civics, using a P74/P75 ECU or any chipped OBD1 ECU makes the wiring relatively straightforward.
- LX/DX/EX (D15B7/D16Z6): Plug-and-play wiring for these models.
- CX/VX (D15B8/D15Z1): Mostly plug-and-play. For 1-wire O2 sensor CX models, wire in the additional 3 wires for a 4-wire O2 sensor setup (Figure 1). For 7-wire O2 sensor VX models, convert to 4-wire. All other wiring connections should be plug-and-play.
OBD2 Engine/OBD1 ECU into OBD1 Vehicle (1992-1995)
Swapping an OBD2 engine into an OBD1 Civic and utilizing an OBD1 ECU is a common approach, requiring specific wiring adjustments.
(Note: Again, for 1992 Civics, VTEC wiring is pre-run; using a 92-95 EX/SI engine harness ensures plug-and-play VTEC.)
D16Y8 with P28 ECU
Using a D16Y8 engine with a P28 ECU in an OBD1 Civic is a popular upgrade.
- EX/Si/VX (D16Z6/D15Z1): Mostly plug-and-play. VTEC remains plug-and-play. The knock sensor will not be used with the P28 ECU. The EX/Si/VX distributor might not directly bolt onto the Y8 head perfectly; however, it can still be used. For full compatibility with the Y8 distributor, an OBD2A or OBD2B to OBD1 adapter harness is necessary. The intake air temperature (IAT) sensor is not located on the Y8 intake manifold. Relocate your IAT sensor to the intake arm (Figure 3) or use a Z6/Z1 manifold, which bolts directly to the Y8 head. Reuse Z6/Z1 injectors as Y8 injectors are not direct plug-ins. For VX models, use EX/SI/DX injectors for similar fuel flow rates to the Y8. Also, reuse the Z6/Z1 alternator as the Y8 alternator uses a different connector style. The CKF (Crankshaft Position Sensor) on the Y8 crankshaft will not be used; secure it out of the way. For VX models, follow instructions to convert the 5-wire O2 sensor to a 4-wire setup.
- LX/DX/CX (D15B7/D15B8): Mostly plug-and-play. Wiring for VTEC solenoid and pressure switch is needed (Figure 1). Reuse the DX/CX distributor as it bolts directly. For Y8 distributor use, an OBD2A or OBD2B to OBD1 adapter harness is needed. Relocate the IAT sensor to the intake arm (Figure 3) or use a CX/DX manifold on the Y8 head. DX injectors can be reused due to similar flow rates. For CX models, upgrade to EX/SI/DX injectors for better flow matching the Y8. Reuse the CX/DX alternator due to connector differences. The Y8 CKF sensor will not be used; secure it.
B16A2/B18C1 (OBD2)/B18C5 with Chipped P28/P30/P72
For OBD2 B-series engines (B16A2, B18C1, B18C5) in an OBD1 Civic using chipped P28/P30/P72 ECUs:
- EX/SI/VX (D16Z6/D15Z1): Mostly plug-and-play. VTEC is plug-and-play. Knock sensor is not used with P28 but will be with other chipped ECUs. An OBD2A or OBD2B to OBD1 adapter harness is needed for the A2/C1/C5 distributor. Relocate the IAT sensor to the intake arm (Figure 8). Reuse Z6 injectors as A2/C1/C2 injectors are not direct plug-ins. For VX, use EX/SI/DX injectors for similar flow rates. Use an OBD1 B-series alternator for plug-and-play compatibility. The CKF sensor on A2/C1/C5 is not used; secure it. For VX, convert the 5-wire O2 sensor to 4-wire.
- DX/CX (D15B7/D15B8): Mostly plug-and-play. VTEC wiring is required (Figure 1). Knock sensor is not used with P28 but will be with other chipped ECUs. An OBD2A or OBD2B to OBD1 adapter harness is required for the A2/C1/C5 distributor. Relocate IAT sensor to the intake arm (Figure 8). Reuse DX injectors; for CX, upgrade to EX/SI/DX injectors for proper flow rates as OBD2 injectors don’t directly fit OBD1 plugs. Use an OBD1 B-series alternator. The CKF sensor is not used. For 1-wire O2 CX models, convert to 4-wire using Figure 1.
B18B/B20B/Z (OBD2) with P75 ECU
Using OBD2 B18B/B20B/Z engines with a P75 ECU in OBD1 Civics:
- EX/SI/VX/DX/CX (D16Z6/D15Z1/D15B7/D15B8): Mostly plug-and-play. Use an OBD1 B18 distributor or an OBD2 LS distributor with an adapter harness. An OBD1 B-series alternator is needed for plug-and-play. For EX/SI/DX, reuse stock injectors; for VX/CX, use EX/DX/SI injectors. The CKF sensor is not used. For 1-wire O2 CX models, convert to 4-wire (Figure 1). For 7-wire O2 VX models, convert to 4-wire.
OBD0 Engine into OBD1 Vehicle using OBD1 ECU
Swapping an older OBD0 engine into an OBD1 Civic with an OBD1 ECU requires some specific adaptations.
B18A (OBD0) with P75 OBD1 ECU
Installing an OBD0 B18A engine with a P75 OBD1 ECU in any 92-95 Civic model:
- EX/SI/DX/CX/VX (D16Z6/D15Z1/D15B7/D15B8): Mostly plug-and-play. The alternator plugs are compatible between OBD0 and OBD1. Reuse EX/SI/DX injectors; for CX/VX, use EX/SI/DX injectors. The OBD0 engine’s fan switch location is on the back of the block, unlike OBD1 which is on the thermostat housing. Rewire the fan switch from the thermostat housing to the back of the block. Polarity doesn’t matter for the fan switch wiring. For VX 7-wire O2 sensors and CX 1-wire O2 sensors, convert to 4-wire using Figure 1.
OBD2 Engine into OBD2 Vehicle using OBD2 ECU (1996-2000)
(NOTE: Avoid mixing 1996-1998 OBD2A and 1999-2000 OBD2B engine and dash harnesses when swapping engines into 96-00 Civics due to different ECU connectors. See Figure 11.)
D16Y8 with P2P ECU
For D16Y8 engine swaps using a P2P ECU in 1996-2000 Civics:
- DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid, VTEC pressure switch, and knock sensor need wiring (Figure 6 for OBD2A, Figure 7 for OBD2B). The idle air control valve (IACV) needs rewiring from 3-wire to 2-wire (Figure 6 & 7). The secondary O2 sensor wiring might need lengthening with an adapter if using an EX-style catalytic converter. Relocate the IAT sensor to the intake arm (Figure 8) as the Y8 manifold lacks a provision.
- HX (D16Y5): Mostly plug-and-play. Reuse VTEC solenoid and pressure switch wiring. 5-speed models need knock sensor wiring as only CVT models originally had knock sensors (Figure 6 – all 96-00 HXs are OBD2A). 7-wire O2 sensors need to be converted to 4-wire.
B16A2/B18C1/B18C5 with P30 (OBD2A)/P2T/P72
For B-series OBD2 engine swaps (B16A2, B18C1, B18C5) with OBD2A ECUs (P30, P2T, P72):
- EX (D16Y8): Mostly plug-and-play. Reuse VTEC, pressure switch, and knock sensor wiring. Secondary O2 wiring may need extending. For B18C1, IABs need wiring to the P72 ECU (Figure 6 & 7). Relocate the IAT sensor to the intake arm (Figure 8). For B18C1/C5, convert to a round-style IAT and place the connector on the manifold (Figure 9 for plug style).
- DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC, pressure switch, and knock sensor wiring are needed (Figure 6 & 7). IACV needs 3-wire to 2-wire conversion (Figure 6 & 7). Secondary O2 wiring might need lengthening. Relocate IAT sensor to the intake arm (Figure 8). For B18C1/C5, convert to round IAT style.
- HX (D16Y5): Mostly plug-and-play. Reuse VTEC and pressure switch wiring. 5-speed HX models need knock sensor wiring (Figure 6). 7-wire O2 sensor needs 4-wire conversion.
B18B/B20B/Z with OBD2A P75
Using OBD2A P75 ECUs (note: 00-01 P75 ECUs with immobilizers are less desirable) with OBD2 B-series engines:
- EX/HX (D16Y8/D16Y5): Plug-and-play. For HX, 7-wire O2 sensor to 4-wire conversion is needed.
- DX/LX/CX (D16Y7): Mostly plug-and-play. IACV needs 3-wire to 2-wire conversion (Figure 6 & 7). Secondary O2 wiring might need lengthening. Relocate IAT sensor to intake arm (Figure 8).
OBD1 Engine into OBD2 Vehicle using OBD1 ECU
Installing an OBD1 engine into a 1996-2000 OBD2 Civic and using an OBD1 ECU involves more modifications.
D16Z6 with P28 ECU
Using a D16Z6 engine and P28 ECU in an OBD2 Civic:
- DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid and pressure switch need wiring (Figure 1). IACV needs 3-wire to 2-wire conversion (Figure 6 & 7). Relocate IAT sensor to intake arm (Figure 8) or rewire to OBD1 style (Figure 9). CKF, EVAP purge, and secondary O2 are eliminated. A D16Z6 distributor needs an adapter. Use Z6 injectors and remove injector “clips” for plug-and-play (Figure 10). Reuse the Y7 alternator or use an adapter.
- HX (D16Y5): VTEC is plug-and-play. Relocate IAT sensor to intake arm (Figure 8) or rewire to OBD1 style (Figure 9). CKF, EVAP purge, EGR, and secondary O2 are eliminated. 7-wire O2 to 4-wire conversion needed. D16Z6 distributor needs adapter. Use Z6 injectors (remove clips). Reuse Y7 alternator or adapter.
- EX (D16Y8): VTEC is plug-and-play. Relocate IAT sensor (Figure 8 or 9). CKF, EVAP purge, EGR, secondary O2 eliminated. D16Z6 distributor adapter needed. Use Z6 injectors (remove clips). Reuse Y7 alternator or adapter.
B16A2/B18C1/B18C5 with OBD1 P30
For OBD2 B-series engines (B16A2, B18C1, B18C5) with an OBD1 P30 ECU in OBD2 Civics:
- DX/LX/CX (D16Y7): Mostly plug-and-play. VTEC solenoid, pressure switch, and knock sensor need wiring (Figure 1). IACV needs 3-wire to 2-wire conversion (Figure 6 & 7). Relocate IAT sensor (Figure 8 or 9). CKF, EVAP purge, secondary O2 eliminated. For 96-98 Civics, use an OBD2 B-series VTEC distributor or an OBD2A to OBD1 distributor adapter. For 99-00, use an OBD2B to OBD1/2 adapter and an OBD1/2 B-series DOHC VTEC distributor. Use B-series injectors (remove clips – Figure 10). Use an OBD2 B-series alternator or OBD2-1 adapter.
- HX (D16Y5): VTEC is plug-and-play. Relocate IAT sensor (Figure 8 or 9). CKF, EVAP purge, EGR, secondary O2 eliminated. 7-wire O2 to 4-wire conversion needed. Use an OBD2 VTEC distributor or OBD2A to OBD1 adapter. Use B-series injectors (remove clips – Figure 10). Use OBD2 B-series alternator or OBD2-1 adapter.
- EX (D16Y8): VTEC is plug-and-play. Knock sensor wiring needed (Figure 1). Relocate IAT sensor (Figure 8 or 9). CKF, EVAP purge, EGR, secondary O2 eliminated. For 96-98, use OBD2 B-series VTEC distributor or OBD2A to OBD1 adapter. For 99-00, use OBD2B to OBD1/2 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
Using OBD1 P75 ECU with B18A/B engines in OBD2 Civics:
- DX/LX/CX (D16Y7): Mostly plug-and-play. IACV needs 3-wire to 2-wire conversion (Figure 6 & 7). Secondary O2 wiring might need lengthening. Relocate IAT sensor (Figure 8). CKF, EVAP purge, EGR, secondary O2 eliminated. Use an OBD2 B18B distributor or OBD2A to OBD1 adapter. For 99-00 Civic, use OBD2B to OBD1 distributor adapter with 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): Relocate IAT sensor (Figure 8 or 9). CKF, EVAP purge, EGR, secondary O2 eliminated. For 96-98, use OBD2 B18B distributor or OBD2A to OBD1 adapter. For 99-00, use OBD2B to OBD1/2 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. For HX, 7-wire O2 to 4-wire conversion needed.
Figure 1: OBD1 ECU Wiring
Figure 2: JDM VTEC Solenoid Bolt Location
JDM VTEC Solenoid Bolt for Honda Engine. This close-up photo highlights the bolt location for installing a VTEC pressure switch on a JDM D15B engine, a necessary step if the engine lacks this component for VTEC system activation.
Figure 3: OBD1 IAT Sensor in Intake Arm
Figure 4: OBD0 and OBD1 Fan Switch Comparison
Figure 5: OBD1 Shocktower Harness
Figure 6: OBD2A Hybrid Pinouts (1996-1998)
Figure 7: OBD2B Hybrid Pinouts (1999-2001)
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
This guide provides a starting point for your Honda Civic or Del Sol engine swap wiring project. Always double-check wiring diagrams and consult reliable sources for your specific engine and chassis combination. Happy swapping!
