Yamaha HPDI Z150, Z175 and Z200 Diagnostics: Reading the Two-Stroke V6 by App

The HPDI models of the Z series are the only two-strokes in this lineup: V6 engines with high-pressure direct injection and their own oil supply. Plenty of them still run fine, but parts and know-how are getting harder to find. That makes it all the more important to know what's going on before you start swapping parts. M-JET DIAGNOSTIC reads the ECU on these engines at the diagnostic connector and shows the values on your phone over Bluetooth.

Which Z models are covered

Covered are the Z150P and Z150Q, Z175G and Z175H, and Z200N and Z200P, plus the counter-rotating LZ150P and LZ200N. Unlike the four-strokes, there's just one ECU variant here. So every engine in the series delivers the same 34 live values, knows the same 12 fault types and offers the same 14 actuator tests. Idle learning is included too.

Live data with two-stroke specifics

• High-pressure side fuel pressure in MPa
• O2 sensor voltage
• Firing state for each of the six cylinders
• Oil plunger pump delivery
• Oil level switches for the remote tank and three switches on the engine tank
• Water separator switch, thermo switch, cooling water temperature
• Engine rpm, ignition timing, injection duration, TPS voltage and throttle angle, atmospheric pressure, intake air temperature, battery voltage
• Kill switch, main switch, shift position, starter relay and the over-rev control release lead

Checking cylinder by cylinder

The actuator tests cover six ignition coils and six injectors one at a time, plus the electric fuel pump and the oil plunger pump. The per-cylinder firing state in the live data is especially useful on a two-stroke V6. If the engine runs rough, you can see whether the ECU registers misfires on one cylinder. Then you fire that cylinder's coil and injector directly. Running the oil plunger pump at the dock makes sense if oil consumption looks suspiciously low or after work on the oil system.

What the fault memory reports

The twelve fault types are easy to keep track of: pulser coil and crank position sensor with irregular signal, thermo sensor, TPS, atmospheric pressure and intake air temperature sensors out of spec, fuel pressure sensor, injector, water in the fuel filter, shift position switch, a tripped kill switch and low battery voltage. For the battery, the ECU's check value is at least 12 V. On an engine that injects at high pressure that's no small detail, because a weak battery quickly shows up as a starting or running problem.

Mechanical checks you have to do yourself

Compression per cylinder, the condition of pistons and rings, reed valves and oil lines aren't covered by any sensor. An HPDI that shows clean values and still runs poorly belongs on a compression gauge. On these engines I'd check battery and fuel pressure first, then the firing state per cylinder, and only after that the mechanical side.

Related topics

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• Test Yamaha Outboard Coils, Injectors and Fuel Pumps One at a Time
• Yamaha F20 to F100 Diagnostics: Fault Memory, Live Data and Component Tests by App
• All Yamaha outboard diagnostics topics

Everything runs via app over Bluetooth, for Yamaha outboards with control unit generations from 2003. Learn more about the M-JET DIAGNOSTIC for Yamaha WaveRunner & Outboard.