Subaru ECM I/O Signal Chart: Engine Speed (Tach) Output Pin B134-23 & Voltages
Reference · 2012-2016 ImprezaAll 3 manual pages
Service-manual diagnostic table listing ECM input/output signal voltages by connector and terminal for engine-off and idling states.
Part of 2012-2016 Subaru Impreza Manual Pages
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)'.
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