JDM OBD2 ECU B Series Swap Guide: Wiring and ECU Solutions for Honda Civic & Integra

Swapping a B-series engine into your Honda Civic or Integra is a popular upgrade, especially for enthusiasts looking to boost performance. This guide provides a detailed walkthrough focusing on OBD2 systems and ECU compatibility, crucial for a smooth swap. We’ll cover wiring intricacies and ECU options to ensure your JDM B series engine integrates seamlessly into your OBD2 chassis.

Understanding OBD2 and B-Series Engine Swaps

When undertaking a B-series engine swap in a 96-00 Civic or 96-01 Integra, understanding OBD2 (On-Board Diagnostics II) is paramount. These vehicles utilize OBD2 systems, which vary between models and years (OBD2a for 96-98 Civic/96-99 Integra and OBD2b for 99-00 Civic/00-01 Integra). The B-series engine, often sourced from JDM markets, might come with an OBD1 or OBD2 ECU (Engine Control Unit), leading to potential compatibility issues. This guide breaks down the necessary steps for a successful swap, emphasizing wiring and ECU solutions.

Engine Mounts, Brackets, and Mechanicals for 96-98 Civic

For 96-98 Civics (EK chassis), ensure you have the correct mechanical components for your B-series engine swap (B16, B18, B20 VTEC, etc.).

Essential Brackets and Mounts

Consider these brackets for a clean and proper engine installation:

99-00 Civic Si Engine Brackets:
- Front transmission bracket
- Rear engine “T” bracket (99-00 Si or JDM EK4/9 “T” bracket is recommended over Integra “T” bracket to avoid pushing the motor too far forward).
- A/C bracket (if retaining AC)
- Left side (driver side) dual-post engine block mount (only needed for B18 swaps; B18 engines typically come with a 3-post right side mount). Alternatively, use a Hasport EK right-side driver replacement mount for both 2 and 3-hole configurations, eliminating the failure-prone OEM liquid-filled mount.
94-01 Integra Brackets (Alternative):
- Front transmission bracket
- A/C bracket

If you want to keep your air conditioning, a “P54” 94-97 Del Sol DOHC VTEC or CRV A/C bracket will support the smaller Civic A/C compressor.

Reuse these stock Civic brackets as they are compatible with B-series engines:

Top transmission mount
Left side (driver side) dual-post bracket

Shift Linkage and Axles

Shift Linkage: For 96-00 EK chassis, 99-00 Si or JDM EK4/9 shift linkage is highly recommended for proper shifter centering. 94-01 Integra linkage may cause the shifter to sit too far back.
Axles: Compatible axles include: 94-01 Integra (all 5-speed models), 99-00 Si, and 94-97 DOHC Del Sol.

With the engine mechanically installed, the next critical step is wiring.

Wiring Your B-Series Swap in a 96-98 Civic: OBD2 Considerations

Wiring is a key aspect of a successful B-series swap. For 96-98 Civics, you can reuse your existing engine wire harness (EWH) or opt for a 96-98 EX 5-speed EWH. OBD1 EWHs are incompatible with OBD2 Civics due to their 2-piece design, unlike the 1-piece design of EK Civic harnesses. Crucially, OBD2a (96-98 Civic) and OBD2b (99-00 Civic) harnesses are not interchangeable.

Wiring Modifications for Non-VTEC Civics

If your Civic is a non-VTEC model, modifying your EWH for OBD1 VTEC engine compatibility involves:

Adding VTEC Wiring: Integrate wiring for the VTEC solenoid (VTS) and VTEC pressure switch (VTPS).
Knock Sensor (KS) Wiring: Wire in the knock sensor.
IACV Mod: Convert the 3-wire Idle Air Control Valve (IACV) plug to a 2-wire plug. OBD1 engines and 96-00 5-speed EX/99-00 Si Civics use a 2-wire IACV.

Image: Wiring diagrams illustrating the IACV mod and A-plug wiring for 96-98 Civics.

VTEC Civic Wiring (EX Models)

For 5-speed EX models, the EWH is already mostly pre-wired for VTEC. However, the secondary O2 sensor wiring is part of the cabin harness, not the EWH. If using a US OBD2 ECU, you’ll need to manually wire in the 2nd O2 sensor. This is unnecessary if you plan to use an OBD1 ECU, as OBD1 ECUs do not monitor a 2nd O2 sensor.

Injector, Distributor, Alternator, and IAT Plug Changes

Adapting an OBD1 engine to an OBD2 Civic requires further wiring modifications for components like the distributor (dizzy), injectors, alternator, Intake Air Temperature (IAT) sensor, and Crankshaft Fluctuation (CKF) sensor.

Distributor Plug:
- Option 1 (Cutting/Splicing): Convert to OBD1 distributor plugs by cutting and splicing OBD1 plugs to your OBD2 EWH, matching wire colors.
- Option 2 (OBD2 Distributor): Use an OBD2 B-series VTEC distributor (96-00 B-series VTEC dizzy), which is plug-and-play (PnP) with a 96-98 EWH. This is the easier solution.
Injector Clips:
- Option 1 (Cutting/Splicing): Convert to OBD1 injector plugs by cutting and splicing OBD1 plugs to your OBD2 EWH, color matching wires.
- Option 2 (OBD2 Injectors): Use OBD2 injectors (96-00 B-series or D-series injectors), which are PnP with a 96-98 EWH.
- Option 3 (Clip Modification): Remove the blue cap inside your OBD2 injector clip and carefully wiggle the clip onto the OBD1 injector. Secure with a zip tie to prevent vibration-induced disconnection.

Image: Illustration of modifying an OBD2 injector clip to fit an OBD1 injector.

Alternator Plug: OBD1 alternators use a round plug, while OBD2 alternators use a square plug.

Image: Comparison of OBD1 and OBD2 alternator plug styles.

- **Option 1 (Cutting/Splicing):** Cut and splice an OBD1 alternator plug to your OBD2 EWH.
- **Option 2 (OBD2 Alternator):** Use an OBD2 B-series alternator (96-01 B-series), which is PnP.
- **Option 3 (Internal Plug Swap):** Disassemble the OBD1 alternator and swap in the inner plug from an OBD2 alternator.

IAT Sensor: OBD2 and OBD1 IAT sensor plugs differ.
- Option 1 (OBD2 IAT): Keep your OBD2 IAT sensor and drill a hole in the intake arm to mount it.
- Option 2 (OBD1 IAT): Cut and splice an OBD1 IAT plug to your EWH to use the OBD1 IAT sensor located on the intake manifold runner.
CKF Sensor: US OBD2 ECUs require a CKF sensor, integrated into the oil pump on US OBD2 engines. OBD1 and JDM OBD2 ECUs do not require this sensor, and JDM/OBD1 engines lack a CKF sensor on the oil pump.
- CKF Bypass Trick: Utilize a CKF bypass method to avoid upgrading to a US OBD2 oil pump. This is crucial for using a JDM OBD2 ECU or converting to OBD1 while avoiding CKF sensor errors with a US OBD2 system.

ECU Options for 96-98 Civic B-Series Swaps

Choosing the right ECU is vital for engine management and meeting emission requirements. Here are ECU options, ordered from easiest to most complex:

JDM OBD2 ECU:
- Pros: Easiest option, direct plug-in to EK chassis, does not require VTPS.
- Cons: Limited OBD2 ECU upgrades, fails US smog tests (incompatible with US OBD2 scanners), 115-120mph speed limiter.
OBD1 ECU Conversion: Using an OBD2a to OBD1 jumper harness with an OBD1 ECU (JDM or US), such as a chipped P28.
- Pros: OBD1 ECUs are highly tunable, forgiving, and do not require 2nd O2 or CKF sensors.
- Cons: Fails smog tests, requires wiring in VTPS.
US OBD2 ECU (Staying OBD2 Spec):
- Option 3a (OBD2a): 96-97 Del Sol DOHC VTEC P30 ECU, 96-99 Integra P72/GSR ECU, or 96-98 P73/ITR ECU.
- Option 3b (OBD2b Conversion): Convert to OBD2b spec with an OBD2a to OBD2b jumper harness and use a 99-00 Civic Si ECU.
- Pros: Can pass smog tests (with successful CKF bypass in Integra or Civic Si chassis; Civic CX/DX B-series BAR’d may also pass).
- Cons: Requires 2nd O2 sensor wiring and functionality.

99-00 Civic B-Series Swaps: Key Differences

Engine installation information for 96-98 Civics largely applies to 99-00 models. Wiring and ECU considerations are similar but with specific nuances.

Wiring for 99-00 Civic

Wiring is similar to 96-98 Civics, but with these distinctions:

Non-VTEC Civic Modifications:
1. VTEC Wiring (VTS, VTPS)
2. Knock Sensor (KS) Wiring (unless using P28 ECU)
3. IACV Mod (3-wire to 2-wire conversion)
4. Distributor Plug Change: 99-00 Civics use a smaller distributor plug. You’ll need a 99-00 Si, 96-98 Civic, or 96-01 Integra large-size distributor plug.

Image: Wiring diagrams illustrating IACV mod and B-plug wiring for 99-00 Civics.

Optional 99-00 Si EWH: Similar to using an EX harness in a 96-98 Civic, switching to a 99-00 Si EWH is suggested. Like EX harnesses, the 2nd O2 sensor wiring is in the cabin harness, requiring manual wiring if using a US OBD2 ECU.

ECU Options for 99-00 Civic

99-00 Si ECU:
- Pros: Easiest option, direct plug-in, compatible with US OBD2 scanners, potentially smog legal (with CKF bypass).
- Cons: CKF bypass needed, limited OBD2 ECU reprogramming, 2nd O2 sensor required.
OBD1 ECU Conversion: OBD2b to OBD1 jumper harness with OBD1 ECU (P28).
- Pros: Tunable, forgiving, no 2nd O2 or CKF sensor requirement.
- Cons: Fails smog, VTPS wiring needed.
US OBD2b ECU (Staying OBD2b Spec):
- Option 3a: 99-00 Si ECU, 00-01 Integra GSR or ITR ECU (requires immobilizer removal).
- Option 3b (OBD2a Conversion – Incorrect in original text, assuming typo and should be OBD2b): OBD2b to OBD2b jumper harness (likely referring to staying OBD2b) and 99-00 Civic Si ECU.
- Pros: Smog legal potential (with CKF bypass), for Integra/Si chassis and potentially BAR’d Civic CX/DX.
- Cons: 2nd O2 sensor required.
JDM OBD2 ECU: Via OBD2b to OBD2a jumper harness, or JDM CTR (PCT) ECU (OBD2b PnP).
- Pros: CKF bypass not needed (as JDM ECUs don’t monitor CKF).
- Cons: OBD2b to OBD2a jumper needed (unless using CTR ECU), fails smog, 115-120mph speed limiter.

OBD2a/OBD2b Integra B-Series Swaps

For 96-01 Integras, engine installation is mechanically straightforward, reusing existing mounts, brackets, axles, and shift linkage.

Wiring for 96-01 Integra

Option 1 (Reuse Integra EWH): Use the existing Integra EWH and follow wiring guides for 96-98 Civic (for 96-99 Integra) or 99-00 Civic (for 00-01 Integra).
Option 2 (US OBD1 EWH): 96-01 Integras have a 2-piece harness design compatible with US OBD1 EWHs. OBD1 VTEC EWH options include: 94-95 Integra GSR, 92-95 Civic Si/EX, 93-95 DOHC Del Sol. For non-VTEC Integras using an OBD1 VTEC EWH, wire in VTPS, VTS, and KS from the ECU plugs to the shock tower plug.

ECU Options for 96-01 Integra

Note: 96-01 Integras have the 2nd O2 sensor in the cabin harness, eliminating the need to wire it in during swaps. 00-01 Integra ECUs have immobilizers, requiring immobilizer removal for swapping.

96-99 Integra JDM OBD2 ECU: Direct PnP. Same pros/cons as 96-98 Civic JDM ECU option.
00-01 Integra JDM OBD2 ECU: OBD2b to OBD2a jumper harness needed. Same pros/cons as 96-98 Civic JDM ECU option.
96-01 Integra OBD1 ECU Conversion: Same pros/cons as 96-00 Civic OBD1 conversion.
96-99 Integra OBD2a US ECU: PnP. Same pros/cons as 96-98 Civic US OBD2 options.
00-01 Integra OBD2a US ECU (Typo in original, likely OBD2b): Same pros/cons as 99-00 Civic US OBD2 options.
96-99 Integra OBD2b US ECU: OBD2a to OBD2b jumper needed. 00-01 Integra ECU requires immobilizer removal for 96-98 Integra compatibility.
00-01 Integra OBD2b US ECU: 99-00 Si ECU is PnP. Pin A15 to A16 fuel pump wire move needed if using 00-01 Integra ECU. 00-01 Integra ECU immobilizer removal or bypass chip required.

Conclusion

Performing a JDM B-series OBD2 ECU swap requires careful planning and execution, especially concerning wiring and ECU selection. This guide provides a comprehensive overview to navigate the complexities of these swaps in 96-00 Civics and 96-01 Integras. By understanding the nuances of OBD2a and OBD2b systems, and the various ECU options available, you can achieve a successful and optimized B-series engine swap. Remember to prioritize safety and consult wiring diagrams and professional resources when undertaking such modifications.