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P1656 fault code: what it means

P1656: Problem in PCM to VTM-4 (4WD) control unit communication. 4WD engagement may not work.

Engine and gearbox (powertrain) · Minor

Usual causes, most likely first

  1. VTM-4 control unit
  2. wiring fault
  3. PCM

P1656 by make

Honda

Problem in PCM to VTM-4 (4WD) control unit communication. 4WD engagement may not work.

Usual causes: VTM-4 control unit; wiring fault; PCM

Lexus

Oil control valve (OCV) circuit on older Lexus VVT-i engines.

Usual causes: failed OCV solenoid; OCV wiring or connector fault

Toyota

Oil control valve (OCV) circuit fault on older Toyota VVT-i engines. VVT stops working; engine can be flat or idle rough.

Usual causes: failed OCV solenoid; OCV wiring or connector fault

Not sure what P1656 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.