What does it mean?
P1586 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Encoding Signal Circuit Not Rational .
Symptoms
- Check engine light on, often with faults stored in other modules at the same time
- Module runs a default configuration, so calibration does not suit the actual engine or transmission
- Noticeably poor drivability, wrong shift points or reduced power
- Some equipment functions are missing or behave incorrectly
- Vehicle may go into limp mode, and on some systems will not start
- Scan tool reports a configuration or variant mismatch
Likely causes
- Control module replaced or reprogrammed without the correct variant coding being written
- Coding resistor or coding plug damaged, missing or fitted with the wrong value
- Open or shorted wire on the coding line between the module and its reference point
- Corroded module connector, with high resistance changing the measured coding value
- Software version in the module not matching the rest of the vehicle after an update
- Unstable supply voltage during a previous programming attempt, leaving incomplete data
- Internal memory fault in the control module
How to fix it
- Read the module part number and software level and confirm they match what the vehicle requires
- Check the service history for recent module replacement or programming work
- Inspect the coding plug or resistor and its connector for damage, corrosion and correct value
- Measure the coding line for continuity, shorts to ground and shorts to voltage
- Check module supply voltage and grounds, and connect a stable power supply before any programming
- Write the correct variant coding for this vehicle and let the module complete its self test
- Replace the module only if it will not accept the coding after the wiring and supply prove good