Fault code P1602 – a step-by-step guide to diagnosing and fixing it

Error code P1602 is displayed and the check engine light is on - what does this mean?

The DTC P1602 is a manufacturer-specific trouble code that mainly occurs in General Motors, Ford and Chrysler vehicles and indicates a loss of communication between the Powertrain Control Module (PCM) and other control units. The OBD system detects an interruption in the internal communication of the engine control unit, which can lead to various vehicle malfunctions. This fault code can have slightly different meanings for different manufacturers, but generally refers to PCM communication problems.

What can cause this fault code?

• Defective Powertrain Control Module (PCM)
• Broken or damaged cable connections to the PCM
• Corroded or loose plug connections on the control unit
• Voltage problems in the vehicle electrics
• Defective fuses in the PCM circuit
• Software error or damaged PCM programming
• Faulty earth connections of the control unit
• Electromagnetic interference due to defective components

What symptoms occur in parallel with fault code P1602?

• Starting problems: The vehicle is difficult to start or does not start at all
• Engine performance: Significant loss of power and uneven engine running
• Shifting behavior: Problems with the automatic transmission shifting
• Electronics: Failure of various electrical systems such as air conditioning or radio
• Indicator lights: Several warning lights illuminate simultaneously
• Emergency running program: The vehicle switches to emergency running mode with limited power

How can I fix the problem with error code P1602?

• Repairing the P1602 requires a systematic approach, as various components can be affected.
• Perform a PCM reset: Disconnect battery for 15 minutes, check and firmly connect all plug connections to the PCM, then reconnect battery and reinitialize system
• Complete wiring check: Check all cable connections to the PCM for damage, corrosion or loose connections and repair or replace defective cables
• Check the power supply: Check battery voltage and charging system, test all relevant fuses and replace if necessary, clean and tighten earth connections
• PCM replacement: If other repairs are unsuccessful, replace the Powertrain Control Module with a new or reconditioned control unit and have it programmed
• Professional diagnostics: Use OBD scanner to read out additional fault codes, analyze live data and have a complete system diagnosis carried out at a specialist workshop