Swapping engines in 1992-2000 Honda Civics is a popular modification for enthusiasts looking to boost performance. This guide focuses on simplifying the engine swap wiring process, particularly when dealing with B-series engines and OBD2 systems. Whether you’re upgrading to a VTEC engine or navigating different OBD versions, understanding the engine harness diagram is crucial for a successful swap. This guide aims to be your go-to resource, covering 95% of the wiring questions you might encounter during your 92-00 Civic engine swap project, predominantly focusing on B and D series engines.
We will primarily concentrate on B and D series engines due to their widespread use in swaps. While H and F series swaps have their nuances, we will provide links to resources for those less common setups. Similarly, K and J series swaps, being more complex, are beyond the scope of this article, but ample information exists elsewhere for those swaps. If you find any areas we can improve or corrections needed, please reach out via private message so we can maintain a clean and focused guide for everyone. The goal here is to consolidate common knowledge and address frequently asked questions, making this information readily accessible and saving you time searching through forums.
Swapping an OBD1 Engine/ECU into an OBD1 Civic
For those working with 92-95 Civics, good news: VTEC wiring is pre-run on the shock tower to ECU harness. Utilizing a 92-95 EX/Si engine harness makes VTEC integration plug-and-play.
D16Z6/D15B (JDM)*/Mini-Me using P28 ECU
*Note: If your JDM D15B engine lacks a VTEC pressure switch, you’ll need to install one. Simply remove the existing bolt and replace it with a VTEC pressure switch from any 90-01 Civic, Integra, or Accord.
DX/LX – D15B7: You will need to manually wire the VTEC solenoid and VTEC pressure switch to your P28 ECU. All other connections should be plug-and-play. Refer to Figure 1 (OBD1 ECU Wiring) for wiring details.
CX – D15B8: Similar to the DX/LX, VTEC solenoid and pressure switch wiring to the P28 ECU are required (Figure 1). If your CX model has a 1-wire O2 sensor setup (non-4 wire), you will also need to wire the three additional O2 sensor connections to the ECU, as detailed in Figure 1.
VX – D15Z1: For VTEC wiring, see the instructions above. For knock sensor and IAB (Intake Air Bypass) valve wiring, consult Figure 1. If you are using a chipped P28 ECU, wiring the IAB and knock sensor may not be necessary. If your VX model utilizes a 7-wire O2 sensor, you’ll need to convert it to a 4-wire configuration. Diagrams for this conversion are available at http://www.hybridautomotive.com/tech/o2/.
B16A3/B17A/B18C1/B18C (OBD1 JDM) using chipped P28/P30/P61/P72 ECU
EX/Si – D16Z6: VTEC is plug-and-play. For knock sensor and IAB wiring, refer to Figure 1. Again, if using a chipped P28 ECU, IAB and knock sensor wiring may be bypassed. All other connections are plug-and-play.
DX/LX – D15B7: VTEC wiring is needed as described above. Knock sensor and IAB wiring instructions are in Figure 1. P28 ECU users can often skip 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 as described above and in Figure 1. Chipped P28 ECU users may not need IAB or knock sensor wiring. For 1-wire O2 CX models, wire in the additional 3 O2 connections as per Figure 1. Other wiring is plug-and-play.
VX – D15Z1: Reuse the existing VTEC solenoid and pressure switch wiring for a plug-and-play VTEC setup. If your VX has a 7-wire O2 sensor, convert it to 4-wire using diagrams at http://www.hybridautomotive.com/tech/o2/.
B18A (OBD1)/B18B in DX/CX/VX/EX using P74/P75 ECU/all chipped OBD1 ECUs
LX/DX/EX – D15B7/D16Z6: Plug-and-play.
CX/VX – D15B8/D15Z1: Plug-and-play. For 1-wire O2 CX models, wire in the additional 3 wires for a 4-wire O2 sensor (Figure 1). For 7-wire O2 VX models, convert to 4-wire using diagrams at http://www.hybridautomotive.com/tech/o2/. All other wiring is plug-and-play.
OBD2 Engine/OBD1 ECU into OBD1 Vehicle
Remember, for all 92 Civics, VTEC wiring is already present on the shock tower to ECU harness, making VTEC plug-and-play with a 92-95 EX/SI engine harness.
D16Y8 using P28 ECU
EX/Si/VX – D16Z6/D15Z1: Mostly plug-and-play. VTEC is plug-and-play. The knock sensor will not be utilized with the P28 ECU. The EX/Si/VX distributor may not directly bolt to the Y8 head. While usable, not all mounting points will align. To use 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 (OBD1 IAT sensor in intake arm)) OR use the Z6/Z1 manifold, which is compatible with the Y8 head. Reuse Z6 injectors as Y8 injectors may not plug in correctly. For VX models, use EX/SI/DX injectors for similar flow rates to the Y8. Also, reuse the Z6/Z1 alternator due to different plug styles on the Y8 alternator. The Crankshaft Speed Fluctuation Sensor (CKF) sensor on the Y8 will not be used; secure it out of the way. For VX models, convert the 5-wire O2 sensor to 4-wire as instructed previously (http://www.hybridautomotive.com/tech/o2/).
LX/DX/CX – D15B7/D15B8: Mostly plug-and-play. VTEC solenoid and pressure switch wiring will be required (Figure 1). Reuse the DX/CX distributor as it will bolt up. To use the Y8 distributor, use an OBD2A or OBD2B to OBD1 adapter harness. Relocate the IAT sensor to the intake arm (Figure 3) OR use the CX/DX manifold, which fits the Y8 head. DX injectors can be reused as they have the same flow rate. For CX models, upgrade to EX/SI/DX injectors for higher flow rates comparable to the Y8 injectors. Reuse the CX/DX alternator due to plug style differences with the Y8 alternator. The Y8 CKF sensor will not be used; secure it out of the way.
B16A2/B18C1 (OBD2)/B18C5 using chipped P28/P30/P72
EX/SI/VX – D16Z6/D15Z1: Mostly plug-and-play. VTEC is plug-and-play. The knock sensor will not be used with the P28 ECU, but will be for other ECUs. To use the A2/C1/C5 distributor, an OBD2A or OBD2B to OBD1 adapter harness is needed. Relocate the IAT sensor to the intake arm (Figure 3). Reuse Z6 injectors as A2/C1/C2 injectors may not plug in correctly. For VX models, use EX/SI/DX injectors for similar flow rates to the A2. Use an OBD1 B-series alternator for plug-and-play compatibility. The CKF sensor on the A2/C1/C5 will not be used; secure it out of the way. For VX models, convert the 5-wire O2 to 4-wire as previously described (http://www.hybridautomotive.com/tech/o2/).
DX/CX – D15B7/D15B8: Mostly plug-and-play. Wire up VTEC as shown previously. The knock sensor is not used with the P28 ECU but will be with other ECUs. An OBD2A or OBD2B to OBD1 adapter harness is required for A2/C1/C5 distributors. Relocate the IAT sensor to the intake arm (Figure 3). Reuse DX injectors as A2/C1/C2 injectors may not plug in correctly. For CX models, upgrade to EX/SI/DX injectors for A2-comparable flow rates, as OBD2 injectors won’t directly plug into OBD1 plugs. Use an OBD1 B-series alternator for plug-and-play. The CKF sensor on the A2/C1/C5 will be unused. For 1-wire O2 CX models, use Figure 1 to convert to a 4-wire setup.
B18B/B20B/Z (OBD2) using 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 for plug-and-play. For EX/SI/DX models, reuse EX/SI/DX injectors. For VX/CX, use EX/DX/SI injectors for plug-and-play. The CKF sensor will not be used. For 1-wire O2 CX models, refer to Figure 1 for 4-wire O2 conversion. For 7-wire O2 VX models, use the previously mentioned instructions to convert to 4-wire (http://www.hybridautomotive.com/tech/o2/).
OBD0 Engine into OBD1 Vehicle using OBD1 ECU
B18A (OBD0) using P75 OBD1 ECU
EX/SI/DX/CX/VX – D16Z6/D15Z1/D15B7/D15B8:
Mostly plug-and-play. The alternator will plug in directly as OBD0 and OBD1 alternator plugs are the same. For injectors, reuse EX/SI/DX injectors, and for CX/VX, use EX/SI/DX injectors. The fan switch location differs on OBD0 engines, being on the back of the block. Rewire the fan switch from the thermostat housing to the back of the block. Wiring order is not critical; use connectors from a junkyard or another suitable wiring method (Figure 4 (OBD0 fan switch/OBD1 fan switch)). For 7-wire O2 VX models (http://www.hybridautomotive.com/tech/o2/) and 1-wire O2 CX models, use Figure 1 for 4-wire rewiring.
OBD2 Engine into OBD2 Vehicle using OBD2 ECU
Important Note: Do not mix 96-98 OBD2A and 99-00 OBD2B engine and dash harnesses when swapping engines into 96-00 Civics, as ECU connectors are different (Figure 11 (OBD2 Harness Comparison)).
D16Y8 using P2P ECU
DX/LX/CX – D16Y7: Mostly plug-and-play. VTEC solenoid, VTEC pressure switch, and knock sensor wiring will be necessary (Figure 6 (OBD2A hybrid pinouts) for OBD2A, Figure 7 (OBD2B hybrid pinouts) for OBD2B). The idle air control valve (IACV) will need to be wired from a 3-wire to a 2-wire configuration (Figure 6 for OBD2A, Figure 7 for OBD2B). The secondary O2 sensor wiring may require lengthening with an O2 adapter if using an EX-style catalytic converter. Relocate the IAT sensor to the intake arm, as the Y8 manifold lacks a location for it (Figure 8 (OBD2 IAT into intake arm)).
HX – D16Y5: Mostly plug-and-play. Reuse VTEC solenoid and VTEC pressure switch. 5-speed models will require knock sensor wiring, as only CVT models originally had knock sensors (Figure 6, all 96-00 HX models are OBD2A). 7-wire O2 sensors need to be wired to 4-wire (eastcoasthondas.com – eastcoasthondas Resources and Information.).
B16A2/B18C1/B18C5 using P30 (OBD2A)/P2T/P72
EX – D16Y8: Mostly plug-and-play. Reuse VTEC solenoid, VTEC pressure switch, and knock sensor wiring. The secondary O2 sensor might need extension if it doesn’t reach. For B18C1, IAB wiring to the P72 ECU is needed (Figure 6 for OBD2A and Figure 7 for OBD2B). Relocate the IAT sensor to the intake arm (Figure 8). For B18C1 and C5, consider converting to a round-style IAT sensor and placing the connector on the manifold (Figure 9 (Round style IAT) for plug style).
DX/LX/CX – D16Y7: Mostly plug-and-play. VTEC solenoid, VTEC pressure switch, and knock sensor wiring are necessary (Figure 6 for OBD2A, Figure 7 for OBD2B). IACV wiring from 3-wire to 2-wire is also needed (Figure 6 for OBD2A, Figure 7 for OBD2B). Secondary O2 sensor wiring may need extension for EX-style catalytic converters. Relocate the IAT sensor to the intake arm (Figure 8). For B18C1 and C5, round-style IAT conversion is an option (Figure 9).
HX – D16Y5: Mostly plug-and-play. Reuse VTEC solenoid and VTEC pressure switch. 5-speed models require knock sensor wiring (Figure 6). 7-wire O2 sensor to 4-wire conversion is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.).
B18B/B20B/Z using OBD2A P75 (Note: 00-01 P75 ECUs have immobilizers, making them less desirable)
EX/HX – D16Y8/D16Y5: Plug-and-play. For HX, 7-wire O2 to 4-wire conversion is necessary (eastcoasthondas.com – eastcoasthondas Resources and Information.).
DX/LX/CX – D16Y7: Mostly plug-and-play. IACV wiring from 3-wire to 2-wire is required (Figure 6 for OBD2A, Figure 7 for OBD2B). Secondary O2 sensor wiring extension may be needed. Relocate IAT sensor to intake arm (Figure 8).
OBD1 Engine into OBD2 Vehicle using OBD1 ECU
D16Z6 using P28 ECU
DX/LX/CX – D16Y7: Mostly plug-and-play. VTEC solenoid and pressure switch wiring are needed (Figure 1). IACV wiring from 3-wire to 2-wire is required (Figure 6 for OBD2A, Figure 7 for OBD2B). Relocate IAT sensor to the intake arm (Figure 8) or rewire IAT to OBD1 style (Figure 9). CKF, EVAP purge, and secondary O2 are eliminated. The D16Z6 distributor needs an adapter. Use Z6 injectors, removing injector “clips” for plug-and-play (Figure 10). Reuse the Y7 alternator for plug-and-play or use an adapter.
HX – D16Y5: VTEC is plug-and-play. Relocate IAT sensor to the 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 is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.). D16Z6 distributor needs an adapter. Use Z6 injectors, removing “clips” (Figure 10). Reuse Y7 alternator or use an adapter.
EX – D16Y8: 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. D16Z6 distributor needs an adapter. Use Z6 injectors, removing “clips” (Figure 10). Reuse Y7 alternator or use an adapter.
B16A2/B18C1/B18C5 using OBD1 P30
DX/LX/CX – D16Y7: Mostly plug-and-play. VTEC solenoid, pressure switch, and knock sensor wiring are needed (Figure 1). IACV wiring from 3-wire to 2-wire (Figure 6 for OBD2A, Figure 7 for OBD2B). Relocate IAT sensor to intake arm (Figure 8) or rewire to OBD1 style (Figure 9). 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 an OBD1/2 B-series DOHC VTEC distributor. Use B-series injectors, removing “clips” (Figure 10). Use an OBD2 B-series alternator for plug-and-play or an OBD2-1 alternator 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 is needed (eastcoasthondas.com – eastcoasthondas Resources and Information.). Use an OBD2 VTEC distributor for plug-and-play or an OBD2A to OBD1 distributor adapter. Use B-series injectors, removing “clips” (Figure 10). Use an OBD2 B-series alternator for plug-and-play or an OBD2-1 alternator adapter.
EX – D16Y8: VTEC is plug-and-play. Knock sensor wiring is needed (Figure 1). Relocate IAT sensor to intake arm (Figure 8) or rewire to OBD1 style (Figure 9). CKF, EVAP purge, EGR, and secondary O2 are 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 distributor adapter and an OBD1/2 B-series DOHC VTEC distributor. Use B-series engine injectors, removing “clips” (Figure 10) or use Y8 injectors. Use an OBD2 B-series alternator or an OBD2-1 alternator adapter.
B18A/B using OBD1 P75
DX/LX/CX – D16Y7: Mostly plug-and-play. IACV wiring from 3-wire to 2-wire is needed (Figure 6 for OBD2A, Figure 7 for OBD2B). Secondary O2 sensor wiring extension may be needed. Relocate IAT sensor to intake arm (Figure 8). CKF, EVAP purge, EGR, and secondary O2 are eliminated. Use an OBD2 B18B distributor or an OBD2A to OBD1 distributor adapter. For 99-00 Civic and OBD2B to OBD1 distributor adapter with either an OBD1 or OBD2 B18A/B distributor. Use B18A/B injectors, removing “clips” (Figure 10). Use an OBD2 B-series alternator or an OBD2-1 alternator adapter.
EX/HX – D16Y8/Y5: Relocate IAT sensor to intake arm (Figure 8) or rewire to OBD1 style (Figure 9). CKF, EVAP purge, EGR, and secondary O2 are eliminated. For 96-98 Civics, use an OBD2 B18B distributor or an OBD2A to OBD1 distributor adapter. For 99-00, use an OBD2B to OBD1/2 distributor adapter and an OBD1/2 B-series DOHC VTEC distributor. Use B18A/B injectors, removing “clips” (Figure 10). Use an OBD2 B-series alternator or an OBD2-1 alternator adapter. For HX, 7-wire O2 to 4-wire conversion is necessary (eastcoasthondas.com – eastcoasthondas Resources and Information.).
(Note: Figures are mentioned in the text but cannot be displayed in this text-only response. Please refer to the original article for Figures 1-11 which are crucial for visualizing the wiring diagrams and components mentioned.)
This guide provides a detailed walkthrough for common engine swap wiring scenarios in 92-00 Honda Civics, with a focus on OBD2 B-series engine harness configurations. Always double-check wiring diagrams and consult professional resources when undertaking engine swaps to ensure safety and proper functionality.
