Which ECM pin is the engine speed (tach) output on this Subaru?

Per the circled row, the engine speed output is on connector B134, terminal 23.

What voltage should the engine speed output show at idle?

With the engine ON (idling), the signal is 0 — 13 V or more, described as a waveform. With ignition ON and engine OFF, no signal (—) is shown.

What are the MAP sensor terminals and expected voltages?

On connector B136: signal is terminal 22 (1.7–2.4 V key on, 1.1–1.6 V at idle), power supply is terminal 16 (5 V), and sensor ground is terminal 35 (0 V).

What should the fuel level sensor read at the ECM?

Fuel level sensor on connector B136, terminal 20, reads 0.12 — 4.75 V both with ignition ON (engine OFF) and at idle.

What voltage does the fuel temperature sensor signal show?

On B136 terminal 12 it reads 2.5 — 3.8 V in both conditions, with the note 'Ambient temperature: 25°C (75°F)'.

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Subaru ECM I/O Signal Chart – Engine Speed (Tach) Output Pin B134-23 & Voltages

Service-manual diagnostic table of Engine Control Module ECM I/O signals with connector, terminal and voltage values

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Service-manual diagnostic table listing ECM input/output signal voltages by connector and terminal for engine-off and idling states.

AI caption March 2021 · Photo 63 of 71

This is a page from a Subaru service manual's ENGINE (DIAGNOSTICS) section showing the Engine Control Module (ECM) I/O Signal table. The table lists ECM inputs/outputs by connector number (B134 or B136) and terminal number, with expected signal voltages in two conditions — Ignition switch ON with engine OFF, and engine ON (idling) — plus notes. A hand-drawn ellipse highlights the 'Engine speed output' row: connector B134, terminal 23, with no signal at ignition ON/engine OFF, and 0–13 V or more while idling, noted as a waveform. Other rows include the malfunction indicator light (B134/17), purge control solenoid valve (B134/14), manifold absolute pressure sensor signal/power/ground (B136 terminals 22, 16, 35), fuel tank pressure sensor signal and ground (B136/21, B136/35), fuel tank pressure control solenoid valve (B134/12), drain valve (B134/13), fuel tank sensor control valve (B134/24), fuel level sensor (B136/20), and fuel temperature sensor signal (B136/12, referenced at 25°C/75°F ambient). The document is useful for identifying the ECM tachometer/engine speed output pin and verifying evaporative emissions and fuel/pressure sensor voltages during diagnostics. The uploader circled the engine speed output row, consistent with the album's tach-adapter project files.

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Frequently asked questions

Which ECM pin is the engine speed (tach) output on this Subaru?: Per the circled row, the engine speed output is on connector B134, terminal 23.
What voltage should the engine speed output show at idle?: With the engine ON (idling), the signal is 0 — 13 V or more, described as a waveform. With ignition ON and engine OFF, no signal (—) is shown.
What are the MAP sensor terminals and expected voltages?: On connector B136: signal is terminal 22 (1.7–2.4 V key on, 1.1–1.6 V at idle), power supply is terminal 16 (5 V), and sensor ground is terminal 35 (0 V).
What should the fuel level sensor read at the ECM?: Fuel level sensor on connector B136, terminal 20, reads 0.12 — 4.75 V both with ignition ON (engine OFF) and at idle.
What voltage does the fuel temperature sensor signal show?: On B136 terminal 12 it reads 2.5 — 3.8 V in both conditions, with the note 'Ambient temperature: 25°C (75°F)'.