I’ve put together a brief summary of the wiring and sensors for the 1998-2001 Geo/Suzuki G13 engine. This 4 cylinder, 1.3L engine is rated between 75-79 HP at 5400 rpm, and is readily available in gently used Chevy/Geo Metros and Suzuki Swifts. It’s light weight and simplicity make it ideal for hovercraft, airboats, and experimental aircraft. It appears most people still prefer to convert pre OBD 2 engines (engines manufactured before Jan 1, 1996), but as these cars age and become more scarce, it is important to explore newer and more readily available options. Newer engines are typically more complicated, but offer greater performance due to innovations like multipoint fuel injection and variable valve timing. When searching for a donor car, I recommend finding a car with manual transmission, and no A/C or power steering. This will make the extraction simpler, but will not have a great effect on the necessary modifications to the wiring harness.

The wiring is fairly complicated, but much of the bulk is devoted to accessories that most builders won’t need (i.e. defrosters, wipers, interior lights, radio, etc.). Below I provide several tables and figures compiled from notes I made during my conversion.

The notes are broken into 4 sections:
1. Completed wiring harness – Picture of the completed wiring harness with all non-critical connections removed.
2. Connector tables – wire outs for the ECU/PCM connectors, with notes on which wires can be removed. In some cases where action such as rerouting of a wire is required to bypass systems (for example, bypassing the clutch pedal switch in the ignition system), there are a series of notes below with more details.
3. Wiring diagrams – detailed diagrams showing connections to the ECU/PCMN, engine sensors, and ignition/charging system. Non-critical wires that can be removed are highlighted.
4. Miscellaneous notes – Tips I’ve compiled to make the Geo/Suzuki extraction and conversion easier.

1. Completed Wiring Harness

Trimmed Geo/Suzuki wiring harness.

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2. Connector Tables

The existing loom will have to be removed to trace wires through the harness. In an old car, the loom is likely brittle, and will need to be replaced anyway.
ECM Connector 1 (C21)
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ECM Connector 2 (C22)
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ECM Connector 3 (C22)
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3. Wiring Diagrams
The following wiring diagram gives pin outs for the three ECM connectors. All critical engine sensors are shown, and systems that can be removed are labeled ‘remove.’ Click on the picture for a larger version.

Though not a great help for modifying the wiring harness, I highly recommend purchasing the Haynes or Chilton manuals to help with removing the engine. As with any source, they are incomplete, but in my experience, the extra information is helpful.