Which ECM terminals connect to the oxygen sensor in this diagram?

The diagram shows ECM coupler terminals B20 and B15 connecting to the heated oxygen sensor, with a Gr/Y wire indicated.

What is the difference between sensor 3 and sensor 3-1 in the legend?

Item 3 is the heated oxygen sensor for 1993 California-spec vehicles only; item 3-1 is the heated oxygen sensor used on other vehicles.

What should be checked before diagnosing with the flow chart?

Verify the air cleaner (clogged), vacuum leaks (air inhaling), spark plugs (contamination, gap), high-tension cords (crack, deterioration), distributor rotor or cap (wear, crack), ignition timing, engine compression, and any other system or parts that might affect A/F mixture or combustion.

What should you do if code No. 13 appears along with another code?

The other code number has priority — check and correct what it represents first, then proceed to the following check for code 13.

What kind of voltmeter is required for these measurements?

A voltmeter with high impedance (MΩ/V minimum) or a digital type voltmeter for accurate measurement.

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Suzuki Samurai Heated O2 Sensor Wiring Diagram - ECM B15/B20 & Code 13 Notes

Heated oxygen sensor coupler wiring and terminal diagram with diagnostic note

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Wiring diagram of the heated oxygen sensor coupler terminals and ECM connections alongside a diagnostic note for trouble code 13.

AI caption August 2006 · Photo 57 of 86

This scanned page is an oxygen sensor (O2 sensor) wiring diagram and diagnostic note page from a Suzuki service manual, uploaded to a 1986 Suzuki Samurai gallery. The diagram shows the ECM (1) and ECM coupler (2) connected via terminals B20 and B15 (with a Gr/Y wire noted) to the heated oxygen sensor. Two sensor variants are shown: item 3, the heated oxygen sensor for 1993 California-spec vehicles, and item 3-1, the heated oxygen sensor for other vehicles. Terminal-side views of both sensor couplers identify the sensor signal terminal, sensor ground terminal, and heater terminal(s). Item 4 is the coupler and item 5 indicates wiring to other sensors. The accompanying NOTE instructs the technician, before following the diagnostic flow chart, to verify that non-EFI systems are in good condition: air cleaner (clogged), vacuum leaks, spark plugs, high-tension cords, distributor rotor/cap, ignition timing, engine compression, and anything else affecting air/fuel mixture or combustion. It also states that if trouble code No. 13 appears together with another code, the other code has priority and should be corrected first. Finally, it requires use of a high-impedance (MΩ/V minimum) or digital voltmeter for accurate measurement. The reference to 1993 California-spec vehicles suggests this page is from an early-1990s EFI Suzuki manual rather than a 1986 model.

This document covers 1993, which may differ from this 1986 Suzuki Samurai.

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Frequently asked questions

Which ECM terminals connect to the oxygen sensor in this diagram?: The diagram shows ECM coupler terminals B20 and B15 connecting to the heated oxygen sensor, with a Gr/Y wire indicated.
What is the difference between sensor 3 and sensor 3-1 in the legend?: Item 3 is the heated oxygen sensor for 1993 California-spec vehicles only; item 3-1 is the heated oxygen sensor used on other vehicles.
What should be checked before diagnosing with the flow chart?: Verify the air cleaner (clogged), vacuum leaks (air inhaling), spark plugs (contamination, gap), high-tension cords (crack, deterioration), distributor rotor or cap (wear, crack), ignition timing, engine compression, and any other system or parts that might affect A/F mixture or combustion.
What should you do if code No. 13 appears along with another code?: The other code number has priority — check and correct what it represents first, then proceed to the following check for code 13.
What kind of voltmeter is required for these measurements?: A voltmeter with high impedance (MΩ/V minimum) or a digital type voltmeter for accurate measurement.