What does it mean?
P1606 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Rough Road Spec Engine Torque ABS-ECU Electrical Malfunction .
Symptoms
- MIL (check engine lamp) on, very often together with ABS and traction control warning lamps
- False or nuisance misfire codes, because rough-road compensation is no longer available
- Traction and stability control disabled
- Speedometer reading erratically if a wheel speed sensor is the root cause
- ABS operating at low speed for no reason
- In many cases no noticeable change in engine performance
Likely causes
- Faulty or contaminated wheel speed sensor, or a cracked and rusted tone ring
- Open circuit, short or corrosion in the wiring between the ABS module and the engine module
- ABS module fault, usually with its own stored codes
- Loss of the bus message that carries the rough-road and torque information
- Poor ground or low supply voltage at the ABS module
- Mismatched tyre sizes or badly worn tyres making the wheel speed comparison implausible
- Software versions of the ABS and engine modules not matched after a replacement
How to fix it
- Scan every module, not only the engine module; ABS codes usually point straight at the cause
- Compare all four wheel speeds in live data while driving slowly and look for one that drops out
- Inspect the wheel speed sensors and tone rings for debris, rust, cracks and physical damage
- Test the signal or communication line between the ABS and engine modules for open circuit, short to ground and corroded terminals
- Check the ABS module supply voltage and ground quality
- Confirm the fitted tyre sizes match front to rear and match the vehicle configuration
- Repair the wheel speed or ABS fault first, then clear the code and confirm the engine code does not return