Fault code P1601 – a step-by-step guide to diagnosing and fixing it

Error code P1601 is displayed and the check engine light is on - what does this mean?

The DTC P1601 is a manufacturer-specific OBD-II fault code that indicates a problem with the communication between the engine control module (ECM) and other control units in the vehicle. This trouble code occurs when the EOBD system detects an interruption or fault in the internal communication of the vehicle electronics. For different manufacturers, this error code can have different specific meanings, but usually refers to communication errors or memory problems in the control unit.

What causes can this error code have?

• Defective engine control unit (ECM/PCM)
• Broken or damaged cable connections between control units
• Corroded or loose plug connections
• Weak or defective vehicle battery
• Problems with the power supply to the control units
• Software errors or damaged firmware in the control unit
• Defective CAN bus connections
• Electromagnetic interference

What symptoms occur in parallel with fault code P1601?

• Check engine light: The check engine light is permanently activated
• Starting problems: The vehicle is difficult or impossible to start
• Irregular engine running: Engine runs unevenly or stutters when idling
• Loss of power: Reduced engine power while driving
• Communication error: OBD scanner cannot establish a connection to the control unit
• Failure of comfort functions: Electrical systems do not function properly
• Emergency running program: Engine only runs in emergency mode with limited power

How can the problem with error code P1601 be rectified?

• Repairing the P1601 code requires a systematic approach to identify the exact cause.
• Check and replace the vehicle battery: Test the battery voltage and replace a low battery, as insufficient power can cause communication errors
• Inspect and repair the cable connections: Check all cable connections between the control units for damage, corrosion or loose connections and repair or replace defective cables
• Cleaning and securing the plug connections: Clean all relevant plug connections with contact spray and ensure that they are firmly and correctly connected
• Software update or reprogramming of the control unit: Carry out a firmware update or have the control unit reprogrammed by a specialist to rectify software errors
• Replacing the engine control unit: If all other measures fail, replace the defective ECM/PCM with a new or overhauled control unit and have it programmed accordingly
• Check the CAN bus system: Test the CAN bus lines for continuity and resistance values and repair any interruptions or short circuits in the network